Archive for the ‘Tech’ Category
Tuesday, January 6th, 2015
In a word, yes! The Zone System (ZS) can be an integral and important part of any digital photographer’s workflow because it allows you to plan and predict an image’s tonal values rather than letting the camera make the decision.
The computerized metering systems in modern cameras are really amazing, and a lot of the time they will give you practical exposures, but in difficult or extreme lighting situations, the scale of the subject’s brightness is simply greater than the camera’s technology can handle. The Zone System:
- Lets you be aware of whether, or how much, the scene brightness exceeds your camera’s limits
- Lets you make an intelligent decision about how to expose when the tones/contrast in a scene are “bigger” than what your camera can capture
- Helps you avoid blown-out highlights
- Lets you know how much exposure range you need for successful HDR captures
Zone System 101
To use the Zone System effectively in the digital world, you need to understand a few of its basic principles.
The ZS was originally conceived by Ansel Adams and fellow photo instructor Fred Archer as a tool to give photographers working with black-and-white negative film (no digital back then!) the ability to plan and control the effects of exposure and development. They created a “scale” of tones from black to white and assigned each one a number, with “I” being almost pure black and “IX” or “X” being nearly white or white. Zone “V” is middle gray, and each “Zone” is one stop lighter or darker than its neighbor.
In the digital age, image contrast can be easily increased post-capture, but there is no practical means of reducing image contrast in a single capture. Pre-exposure can enhance shadow tonality, but this requires the ability to double-expose, and High Dynamic Range techniques (HDR) require three or more exposures for best results. And while HDR techniques can accommodate a wide range of brightnesses, the end effect often appears contrived and unreal.
Sophisticated “evaluative” metering modes in modern cameras can handle many complicated shooting situations, but if the contrast of the scene exceeds the recording scale of the camera, something’s gotta give. This is where the ZS can help.
Do you need a reliable hand-held spot meter? A 1° measuring spot lets you measure important areas precisely and with ease. Using a camera’s “spot” metering mode is not always practical: the size of the spot depends on the focal length of the lens and generally requires a lot of button-pushing and pointing the camera this way and that – an exercise in frustration and wasted time.
Without a spot meter, you may know that you will lose tonality at one end of the scale or the other, but you have no way of knowing which, or by how much, at least until examining an after-the-fact histogram. By then, your scene might be gone!
That said, if a spot-meter is just not going to be in your bag of gear, you can do the test below by filling your metering area with the gray card only, and proceed as if that were a spot reading. You will at least be able to determine your dynamic range.
Spot Meters and the Zone System. By design, all light meters will give you an exposure to make the measured area middle gray. This gray is called Zone V. If you measure snow in sun, the meter will give you the exposure to make the snow Zone V gray. If you measure a black speaker grille, it will give you the exposure to make that grille Zone V gray. If you want the snow to look white (not paper white but a very light gray) you need to PLACE it on a higher Zone. If you give one stop more than the meter says, you are placing the snow on Zone VI, two stops more than the basic meter reading places that value on Zone VII, and so on. As for the speaker grille, it is just the opposite. You would need to expose the grille two or three stops LESS than indicated in order to make it look dark. This would PLACE the grille on Zone III or II respectively. You can only PLACE one value. Everything else, then, FALLS in natural relation to the placed value. A Spot Meter just makes it possible to measure small areas such as a small highlight or important dark value.
The following illustration was made using a Canon 5D MkII digital camera. The first and third images were made with the camera set on Program, letting the camera evaluate the white figurine on a white card and an egg on a black card. The sophisticated computer-based metering system assumed everything it was looking at was gray, and rendered it as gray in the capture. In the second and fourth images, I used a Pentax 1° digital (readout) spotmeter and placed the white card in the second image and the egg in the fourth image just brighter than Zone VII, rendering them as near-white. No guesswork.
Know your limits. In order to plan a ZS approach to exposure, you need to know what tonal range your camera can and can’t handle. The composite image below shows nine images made with the Canon 5D set on MANUAL exposure. The target was a Kodak Gray Card with white and black patches that I made many years ago for testing the tonal range of slide film. I set my Pentax Digital Spot Meter to the same ISO as the camera, took a reading of the gray card and exposed according to the meter (a Zone V middle gray). I made four darker exposures one stop (Zone) apart and four lighter one stop apart.
At three stops under the Zone V exposure, I had made the gray card almost as dark as the black patch, so that told me the camera could hold some tonality for a subject on Zone II. On the bright end, the gray at two stops brighter than Zone V was still a noticeable light gray compared to the white patch, but at three stops (Zone VIII) the gray had turned as white as the white patch. That told me that my upper limit for recording highlight tonality is about Zone VII-1/2, or five and a half stops total range.
Measure your subject highlights. In general, with digital (and color transparency film), images look their best when the highlights are not blown out. If a photo opportunity is fleeting or moving, and I only have one chance for a shot, I will take a quick spot reading of an important high value, maybe a white dress or bright cloud, and give it an exposure of about 2-1/2 stops brighter than the basic meter reading (Zone V). This PLACES that dress on Zone VII-1/2. Having already done the test above, I KNOW that it will be very bright, but not “blown out”!
With digital, there is nothing evil about some subtle bracketing, so if you have the opportunity, go ahead and give some + and – exposures. With some practice and your spot meter, though, you’ll be surprised how often you get it right the first time! You might not need step five!
Measure your subject range: If you suspect the range of brightness in the scene is significantly beyond the range of your camera, AND you have the opportunity to make multiple exposures of a stationary subject, you can use HDR techniques. The ZS can be a big help here, too. Rather than making random plus-and-minus exposures to cover subject brightness (dynamic range), you can quickly measure exactly how much range you need to cover.
Let’s say I have a tree in the foreground in deep shade with some textured charring on its trunk. In the same composition I have bright sun glaring off some pale boulders.
With just two spot readings I can determine the range and how to deal with it. First I’d read the charred trunk. Based on my test above, I would know that if I gave it a Zone II exposure it would still have tonality. That determines the shadow exposure. Then I’d read the bright rocks. Let’s say they measured 8-1/2 stops brighter than the trunk. That is 3 full stops brighter than what my camera can record. So I now know that AFTER my first shadow exposure, I need to make 5 or 6 more exposures each at ½ or 2/3 faster shutter speed than the exposure before, until the last exposure is at least 3 stops darker than the first. Then it’s time to let Photoshop CS5 and/or other preferred software combine the exposures.
Keep in mind that the Zone System is not dogma! Its application should be considered as something deeply personal. If you simply have a hunch that you like a certain shadow two stops darker than a basic meter reading (Zone V) rather than three, do it that way! It’s really a lot like cooking. If YOU like YOUR veggies al dente, don’t “expose” them to so much heat that they are over done! Bon appétit!
Tuesday, February 11th, 2014
Apt Question from FaceBook reader Harry Green.
“Any suggestions on how to be water conscious these days in Southern California. Our water prices are high, and I fret to think of those days I left water on for 8 hours, while printing for 8 hours. How to survive ? I used to wash DW prints and use hypo clearing agent. What is practical now a days.”
Thanks for the question!
I went through 2 rationed droughts in Carmel while I was working for Ansel and another in San Francisco when I had my studio there. Typical ration then was 50gal/day per person/per household. Because photography was a profession, Ansel got an extra allowance, and so did I in San Francisco. But all the dedicated artists were stuck with 50gpd.
• DON’T leave the water running.
• DO change the water in your print-holding tray several times during a print session.
• DO use a hypo-clear or proven wash-aid for film and prints.
• DON’T run a toning or wash load except for a “full” load. If prints have been rinsed well, they can be screen-dried after initial fix/rinse and kept aside until a full load is ready.
• Current archival standards do NOT call for elimination of all traces of fixer. We can get by with MUCH less than we thought in the late ’70s. In the words of RIT’s James Reilly at the Image Permanence Institute: “DO tone your prints. DON’T over-wash” A modest trace of fixer actually acts as an anti-oxidant. A light tea color with an HT-2 test is a good guide.
• Washing. It can be tedious, but you can save a huge amount of water by using dump-and-fill methods for film, or cycling between trays of clean water for prints rather than using an archival washer with running water. You can safely wash 2 rolls of 120 film with 2 gallons of water!
More on fixing and washing:
Answer to a comment advocating trashing the hardener bottle that comes with Kodak Rapid Fixer:
I generally buy Ilford fixers. I usually get the Hypam, because it can be used with or without a hardener. I process my sheet film in trays, so I add a hardener for that, but I use it without the hardener for prints. The Kodak Rapid fix DOES come with a bottle of hardener, but like the Hypam, you can use it or not. I use the fixers 1:3 for film and1:4 for prints – single bath only, 45 seconds with agitation. Among its other assets, selenium toner is ALSO a test for residual silver (adequate fixation). If your prints do not stain in selenium it is proof that they were fixed adequately. I do recommend using a wash-aid, but I personally have neither the time nor energy to wash each print by hand, and the more a print is handled, the more it is subject to physical damage.
Hope these tips help!
Tuesday, February 11th, 2014
When Ansel hired me in July of 1974 to be his assistant in Carmel, he actually hired me to be his #2 assistant. Ted Orland had already been on board for about two years, working Monday through Friday. Ansel, not personally having any concept of “time off,” wanted to work seven days a week and hired me to work Friday through Monday.
- Ansel’s routine was to print in the morning during the regular week and do the selenium toning and washing in the afternoon after lunch. Being Ansel’s regular assistant, Ted would be in the darkroom for the morning sessions, and I would be called in to help with the toning and washing. In those days, “archival” print washers were anything but mainstream, and things were pretty basic in the Carmel darkroom. Prints 11×14 and smaller were washed in a big rotating “squirrel-cage” washer, and 16×20 and 20×24 prints were all washed by hand – moving batches of prints from one tray of clean water to another, dumping the first tray and filling it with clean water, moving the prints back to that tray and dumping the second tray, and so on, until maybe 10 or 12 exchanges had been made. Tedious and exhausting, but as it happens that process uses relatively little water and gets prints extremely clean.
After I had been on the job for several months, Ted left to carve out his own career, and I was then “first” (and actually only) assistant. I wasn’t married or busy with a lot of activities during the weekends and often popped by the house, helping out with this-or-that on a Saturday or Sunday, so my old position of Friday-to-Monday assistant was left vacant.
So now, the darkroom truly came to be my domain. What an experience!
Setting the Stage
Ansel’s darkroom was purely functional and consisted of nothing elaborate. In fact, nothing about Ansel was elaborate! He drove a Ford LTD which he bought used. His “sound system” consisted of an old mono amplifier, an old turntable and one speaker built into a wall. He rarely turned it on. Except for the Hasselblad, even his camera equipment was a mish-mash of rather tattered gear. One lens didn’t even have a brand name on it, but it sure was sharp!
The darkroom itself was long and narrow, with three sinks taking up most of the length of one wall and enlargers along the other. One end of the darkroom, next to the pocket entrance door, was a chemical-mixing counter with various chemicals on shelves above, and drums of Hypo crystals below. At the opposite end of the darkroom there was a “panic door.” This was intended as an emergency exit in case of earthquake or other calamity. (Ansel’s nose was broken in an aftershock of the 1906 San Francisco earthquake and he was somewhat fixated on that particular risk!)
The layout of the darkroom was principally engineered to accommodate the making of “mural” sized prints. His 8×10 enlarger was built by San Francisco’s Adolph Gasser out of an old 11×14 studio camera and set up to project its image horizontally. The machine ran on tracks on the floor and projected an image on an 8-foot tall vertical easel which also rolled on the same tracks. The lightsource consisted of a bank of 36 50-watt reflector bulbs, each on its own on-off switch. If Ansel wanted to give a general “dodge” to part of an image, he could turn off the lamp illuminating that region. The easel was faced on front and back with metal sheet, so paper could be attached firmly with magnets. A roll of mural paper could be inserted over a crossbar at the top of the easel and the paper pulled down like a window blind and held flat with magnets. On the opposite side of the easel and 8×10 enlarger was a counter which held two 4×5 Beseler MCRX enlargers. One of the Beselers had an innovative lightsource (Codelight) for printing on variable-contrast papers, and it could be turned towards the rolling easel and tipped up for horizontal projection in case he wanted to use it for big prints. The other Beseler had a condenser lightsource and was rarely used except for demonstration.
One staple of nearly every darkroom was absent in Ansel’s–an enlarging timer. There wasn’t one. Being a musician from his early teens, he was accustomed to counting beats, and had an electronic metronome set at 60 beats per minute. Every print he ever made in a darkroom of his own was made by simply counting seconds! This augmented his creative control immensely. Time was not something some gizmo measured and ruled, time was a deeply rooted internal feeling for Ansel. Twenty-two seconds felt like twenty-two seconds!
On the sink side, there was a long, fairly narrow sink for processing, with a ledge at the back for chemical containers and a wide ledge at the left and right for developer and fixer containers. On the left there was a 15-gallon stainless tank that held the Dektol stock solution, and on the right there was a 25-gallon tank that held the F-6 formula fixer we mixed from scratch. A shelf over the back of the sink held the metronome, various graduates and sundries. To the right of the processing sink was an approximately 3×3-foot print holding sink. To the right of that was another large sink, about 4×6-feet which held the squirrel-cage washer and maybe another rinse tray. If Ansel were making mural prints, the equipment could be removed from the sink and a wet 42×60-ish mural print could be laid flat.
In use, with the door closed on the long, narrow room, with white lights off, amber safelights on, water running, exhaust fans on and the rhythmic beep of the metronome, it had all the feeling of being in a fantasy submarine!
Coming up: A Days Work
Tuesday, April 9th, 2013
In Part I of this blog on how to create a more expressive image, I talked about visualization–the difference between what the camera sees (the literal) and what the photographer sees in his or her mind’s eye as the final print (the expressive.)
The two may be quite similar or quite different, but being able to interpret what you see and picture the final image on paper is critical to the making of an expressive image because it dictates what techniques and equipment will be required to execute your vision successfully.
The first consideration is point of view–choosing the proper vantage point for camera and lens. This may seem almost simplistic, but you would be amazed at how many strong, compelling visions are lost in the final image because the photographer didn’t take the time to find the most favorable position.
Why does it matter so much? If you don’t set your camera and lens in the rights spot, you may wind up with elements in your final image that compete with your vision and weaken it. And yes, you can fix some of these things with cropping and Photoshop, but not always, so it really pays to get it right from the beginning.
I’ll use a photograph I did not long after I moved to Santa Fe to demonstrate the things to consider when choosing your vantage point. This is a wonderful old adobe about 15 minutes from house. Interesting to note that shortly after I made this image, the fence and gate were replaced with a tall wall, completely obscuring the building behind. Great example of why, if you see something you’d like to photograph, do it now!
Gate and Windows, Galisteo, New Mexico 1996
The first thing I did after I decided to photograph this beautiful building was to use my cut-out card with a hole the same shape as my film (see part I of the blog). This helped me evaluate the various aspects of the scene as elements in a clearly defined structural arrangement.
I also looked through the card with just one eye so that I could see the subject in two dimensions rather than three. And by “cropping out” much of the detail surrounding the scene I wanted to photograph, it was much easier to concentrate on the relationships of the objects within the scene to each other.
Now that I had the basic scene isolated and determined, I had to decide where the best vantage point would be. And vantage point includes not only your position with your tripod, but also the exact position of the lens.
I thought about whether I should stand near or far and experimented, again using my cropping card. I moved closer to the scene and noticed that the gate would be larger than I wanted relative to the size of the windows. When I moved back from the scene, the gate was not as prominent as I wanted. I ultimately chose a position that gave me a relationship that felt right.*
The other consideration in choosing a vantage point and setting up the camera is where the lens should be–up, down, left or right? In my image, if I lowered the lens too much, the pickets at the left would run into the little window, and I would see the threshold of the door through the gate. If I raised the lens too high, the pickets merged with the bottoms of the two larger window frames. The left/right position was carefully chosen so that none of the picket points ran directly into any of the architectural features in the background.
Lens & Filter
Although I will be going into detail about lens choice and filter use in the next installments of this blog, I thought I would mention each briefly here for the sake of understanding how I approached realizing my vision in this photograph.
The choice of a focal length helped refine the exact lens position. I had framed the subject with my hands and knew where I wanted the framed edges to be (cropping). I already knew where I wanted to stand near-far, so choice of lens was simply to pick up the one that gave me the angle of coverage I wanted.
Another consideration was whether to use a filter. In this case, the adobe wall of the house was a deep reddish-brown. I decided to use a strong green filter to darken the wall relative to the white fence and gate.
Bottom line when considering point of view….take your time in setting things up, don’t just happen on the scene and click away. Don’t be afraid to experiment by moving around a bit and seeing what happens when you move in, back, left, right or even up! It doesn’t have to take hours, but paying attention to the details at the beginning will help ensure a better image in the end.
* Note: I mentioned that I chose a position that felt right to me. There are numerous “formulas” for determining compositional structure–the Rule of Thirds, the Golden Sector and others. I have personally never used any of these because I have always felt comfortable with my own sense of “balance.” But if employing one of these time-tested structural aids helps to refine your own seeing, I certainly encourage it.
I’ll leave you with a short quote from Mark Twain in his essay, Fennimore Cooper’s Literary Offenses, “Eschew Surplussage!” In other words, if it doesn’t contribute to your statement, leave it out!
- Choosing the right lens to properly frame the subject
- Knowing enough about filters and exposure to record subject tones in the most useful way
- Following through in the darkroom or computer lab, aka the “light” room
Sunday, September 16th, 2012
How Do Light Meters Work?
Most of us can understand that a reliable light meter, either in-camera or hand-held is pretty essential to getting good film or digital exposures – but just how they work might be a matter of some mystery or confusion!
When light meters were first made, they were pointed from camera position toward a scene, measuring a rather broad area, evaluating the average brightness of objects either emitting light or reflecting some amount of light back toward the camera. The assumption was that if you mixed all the lights and darks in an “average” scene into one brightness, that mixture would be some sort of middle gray.
It was decided that that middle gray represented a neutral color reflecting 18% of the light falling on it. Photoshop-wise – that works out to a black set at about 55% opacity.
In photography, this works out fine so long as your meter (or camera) is reading an equal mix of lights and darks, or you are metering something that is itself middle-gray in brightness.
• But what if you are photographing a white horse in the snow? The meter thinks it is looking at something gray – and thus will give you the correct exposure to make that horse and snow GRAY! The solution is to give MORE exposure to your film or image sensor so that the scene is given enough light to look like a textured white in the image.
With film, this is about 2.5 to 3 stops more light than your meter reading.
With digital, this may be only 1.5 to 2 stops more light than the meter reading.
• Conversely, if you are photographing something dark in a dark surround, the opposite approach comes into play. The meter will tell you how to expose to make that DARK scene a middle gray! You then need to give LESS exposure to force that scene to look dark.
With film: a 2 to 3 stop reduced exposure will run you from a textured dark to nearly black.
With digital: a 1.5 to 2.5 stop reduction will typically run you from a textured dark to nearly black.
(Pssst: that’s pretty much the real basics of the Zone System! Hint – that 18% “middle-gray” is Zone V…!)
A word of caution: Some, if not many, of the modern in-camera meters with computer analytics can come up with completely unpredictable exposures. First, they seem to all be calibrated towards acceptable exposures for color slides or digital – so if you are working with a bw negative film (and to some extent color neg) you are almost certain to get a good looking contact sheet with terrible shadow detail. Second, computer analytics are not the same thing as thinking! The most sophisticated metering system in existence has no idea of WHAT it is analyzing! If you want to be in control of image tonality, you need to have an understanding partnership with your metering system and equipment.
Tuesday, June 19th, 2012
Polarizing Filters – You can’t mimic these in Photoshop!
A polarizing filter is one of the few filters that is equally effective with color imaging and with black-and-white. It can:
• Minimize or eliminate reflections in glass, water or most any surface except metal.
• Darken skies in color photos as well as in black-and-white
• Cut through haze
• Increase the saturation of colors
Types: There are two basic types of polarizer, the original “linear” polarizer and the comparatively new “circular” polarizer. They essentially accomplish the same thing, but linear polarizers pose problems with most modern through-the-lens metering systems, so circular polarizers were developed to minimize or eliminate metering issues.
Filter Factor: Most filter manufacturers list polarizers as having a variable filter factor, usually 2 to 4 depending on the effect of the polarization. I personally just use a factor of 2.5 (1.3 stop correction) because any further darkening, say, of a sky is an effect I want, and do not want to override.
Use: The great thing about using a polarizer is that you can actually see the effect before taking the picture. When held up to the eye or placed on a lens and rotated in a clockwise or counter-clockwise direction, you can see gradual lightening or darkening as you rotate. You can pick just the degree of effect you want. At its lightest orientation, it is essentially just a 1.3-stop neutral density filter. If you are using aa non-through-the-lens camera (rangefinder, Holga, etc) you will need to hold the filter up to your eye and note what part of the filter is at “12 o’clock” for the effect you want, then put the filter on your lens in the same orientation.
Above, a polarizer effectively eliminating reflections in glass. Note that the reflections in the polished table are only moderately affected – that light was polarized in a different direction. Below, note how the polarizer has darkened the sky, increased saturation in the colors and reduced haze.
Using Polarizers with Wide Angle Lenses: Polarizers work by darkening light in the subject that is already polarized. If there is no polarized light, the filter has no effect other than neutral density. The light in a sky is not evenly polarized, so if you are using a wide-angle lens, you will capture part of the sky that may be highly polarized AND also include part of a sky that is less polarized. If you are using a wide-angle lens on a subject that does not include sky, you may not notice any odd effect.
In the end, no well equipped camera case should be without the versatile polarizing filter!
Sunday, May 6th, 2012
A previous post discussed the basics of how and why colored filters can change the relationships of different subject colors in black-and-white photography. This writing will give some visual examples of the effects of filters in BW work.
The example above shows a still-life scene containing a wide range of neutrals and colors, rendered in color, black and white with no filter and then with four strongly colored filters. The effects are commensurate with the color-wheel in the previous post:
#12 Yellow. The lemon and banana are lightened significantly. The near-yellows – red, orange, green are lightened somewhat. The cyan bowl is darkened. Neutrals unchanged.
#25 Red. The lemon and banana are not quite as light as with the yellow filter, but the tomato, radishes and apple have become quite light. The cyan bowl is now quite dark. Neutrals unchanged.
#58 Green. It has turned its opposite and near opposites, radishes, tomato, apples near black. The lettuce is lightened somewhat. Neutrals unchanged.
#47B Blue. Wowzer! But consider – yellow is opposite blue, and red and green are adjacent to yellow. It darkened everything – except the cyan bowl, which it lightened because that color is its neighbor!
A note: Red or Green with foliage. Green plants and trees don’t always behave the way one might think! Living plants also reflect a great deal of infrared. Broad-leaf plants usually lighten with a green filter, Junipers and piney growths usually do not.
As I mentioned in the previous post, digital images are best “filtered” post-capture. The examples shown here should suggest the post-process effects.
Next time – polarizing filters! You can’t mimic these in Photoshop!
Friday, April 6th, 2012
Filters – How to Choose and Use
I think the thing I like most about working in black-and-white is the fact that it’s much more an expression of how I feel about a subject than a representation of “reality.” The world doesn’t exist in Black-and-White (my mother told me that…) so a b/w image is by its very nature an abstraction of the things we see.
The judicial use of filters can greatly enhance the impact of how a subject appears, and in black-and-white we can even skew the way colored subjects relate to each other.
I normally like to be fairly subtle about my use of filters; a photograph shouldn’t look like a filter was used, just as a print shouldn’t look like it was dodged and burned! One of the most generally popular choices, a #8 Yellow, is usually so subtle that I don’t see much point in using it. Another popular choice, the #25 Red, is often too strong, rendering skies and day-lit shadows illogically dark.
My two favorite filters, a #12 Yellow (“minus blue”), and a #23 Red, respectively, have both more strength and finesse than the ones found in most camera bags. The #12 yields an effect almost as strong as a #15 orange, but with only a 1 stop filter factor, only slightly greater than the #8. The #23 tends not to make skies quite so artificially dark as the #25.
Understanding the relationships of different colors of light to each other is key to choosing a filter. A standard color-wheel is shown below. The numbers in various color areas are Wratten filter-number designations, an industry standard utilized by many filter manufacturers. A #12 filter, for example is pure yellow, a #8 is a light yellow. The capital letters in bold are called Additive Primary colors, and the lower-case letters are Subtractive Primaries.
Red is opposite Cyan
Green is opposite Magenta
Blue is opposite Yellow
In Black-and-White photography the practical effect of a filter is to lighten its own color and darken its opposite color.
In purely scientific terms, a filter has no effect on its own color and darkens everything else, including “neutral” colors. When we apply a “filter factor” to the exposure, neutral colors remain unchanged and then the filter’s own color becomes lighter and its opposite becomes darker.
What we commonly call a “blue” sky is technically a bit more cyan, which is why a red filter will darken the sky more than a yellow filter. Orange is in between. Keep in mind that outdoor shadows are illuminated by the sky, not the white light of the sun. Any filter that darkens the sky will also darken the shadows!
Green or red filters can be quite useful in the Southwest, for example, where we might come across a brilliant green plant in front of a red sandstone wall. With no filter used, the b/w film will see the green and red as being largely the same: gray mush. A strong green filter will make the plant light and the sandstone dark, the red filter will do the opposite.
For workers using digital cameras for b/w, my tests indicate that it is better to use a computer-simulated “filter” after a RAW capture, rather than an actual filter for the capture itself. While this may only approximate the effect of using a filter with film, the effect ought to be similar – without any need for exposure compensation for the filter’s own density.
Polarizing filters are also extremely useful for both B/W and color work – but we’ll cover that in another post!
Friday, March 16th, 2012
Where do you focus, and how does the aperture affect an image?
In a certain way, the opening question should be the other way around! There is a law of physics that governs the relationship between shutter speed and aperture (f-stop). Shutter speeds are pretty easy to understand: 1/60 second is one half as much time as 1/30. F-stops are a little different: f8 is one half the light of f5.6, which is half the light of f4! The point is, for any shutter speed/f-stop combo, one-half the exposure time with twice the light equals the same total amount of light given to the film – or pixels. 1/60 @ f4 = 1/30 @ f5.6 = 1/15 @ f 8.
There is always the inescapable relationship between exposure time and aperture. If you are photographing a sports event, you will likely go with a fast shutter speed and let the aperture fall as it will. This article will “focus” on aperture as primary.
F-stop #s versus depth-of field. A lens can only truly focus on ONE plane. With a perfect lens, that plane would be equally sharp at any aperture – but everything nearer or farther would rapidly become unsharp. Increasingly smaller apertures reduce this apparent unsharpness, increasing what is called depth-of-field. The smaller the aperture (f16 is smaller than f4), the greater the apparent sharpness.
In the example above, figure A is focused approximately on the line of traffic in the foreground. The chain-link fence is way out of focus, as is the distant railing. The wide-open aperture (f 1.4) necessitated a very fast shutter speed resulting in the cars frozen in time. Figure B is with the lens stopped down 4 stops (f 5.6). The point of focus was not changed, but the fence is now a good deal sharper, as is the distant railing, but at the now much longer exposure time, the nearby car, while still sharp in focus, is blurred in time. Figure C is still focused in the same place but the lens is now stopped down 3 more stops to f 16. The fence now appears to be quite sharp as does the distant railing, but the car is now quite blurred at 1/15 second. (Note: it is a total coincidence that the images seem to show the same car!)
Most fixed-focal length lenses have an engraved scale allowing you to evaluate how much apparent sharpness (depth-of-field) you can get at various apertures. The example above shows a Hasselblad 80mm lens set at f 22. As the lens aperture is stopped-down, the depth of field increases in the proportion of 1/3 toward the lens from the plane of critical focus and 2/3 beyond the plane of focus. Figure A above shows the lens focused at about 3.3 feet, and at f 22 the depth of field runs from 3 feet away to 4 feet. Figure B shows what would happen if we did a landscape with the lens focused on infinity. The image would only be “sharp” from about 17 feet away to distant mountains. If we instead focused at 17 feet (this is called the “hyperfocal” distance) the image would now be sharp from about 9 feet to the mountains (Figure C).
There are two ways to plan how to make this work. One way is to choose your aperture first and see how much depth-of-field you get, and the other is to find out what aperture you need to work with and then see how much depth of field you need to work within. Let’s say your camera is on a tripod, and you want as much as possible near-and-far to be sharp. Take the Infinity mark on the lens and place it over the engraving for your smallest aperture. The lens is now focused automatically at the hyperfocal distance and you can read the depth of field on the focus scale of the lens. In this example (Figure C), f 22 gives you a pretty sharp image from about 9 feet to infinity. Lets say the camera is NOT on a tripod, and you can’t manage to stop down to f 22, but only to f 8. In this case, you would place the Infinity mark over the f 8 index. You would now see that the image would only be sharp from about 20 feet to infinity (see green arrows, figure C).
What if your lens doesn’t have markings? A lot of modern zoom lenses have distance scales, but no depth-of-field markings. If this is the case, you can find the hyperfocal distance by putting the nearest subject and distant subject marks on the lens an equal distance from the central focus mark. If your camera has a “depth of field preview” button, this can be a useful aid in seeing just how much is sharp – or not! But the actual depth of field for any given f-stop will just be a guess.
One bit of fun with f-stops: Selective Focus! Sometimes, you can make a stronger statement by limiting how much is in focus. Just leave the lens at its widest aperture. The figure on the left was done with a 200mm lens at f 4.5 focused exactly on the near marker, and the figure on the right was done at f 22 with the lens set at the hyperfocal distance.
One last thing I’d like to comment on in this writing: lens quality. Photo gear can be expensive, no doubt about it. Especially at an entry level, the prospect of getting an off-brand lens for a lot less than the brand that has your camera’s name on it can be awfully tempting. In these days of computer-aided engineering design a “Brand X” lens can be quite good – but there is an equally good chance that it will not measure up to the quality or durability of a top brand. One of the reasons being that the Brand X lens manufacturer can cut a lot of production cost by using much looser manufacturing tolerances than the top brands. The glass itself may well be of lesser quality. If you need to save dollars, look for quality used gear from a reputable source.
Hopefully, all of this will help you have a better understanding of the relationship between your vision, your lens, and your results!
Friday, March 9th, 2012
As I discussed in a previous blog, effective application of the Zone System (ZS) really requires the use of a reliable hand-held spot meter. There are basically two kinds of spot meters, those with analog dials for calculating exposure and those with digital displays. While both can afford effective results, the ones with analog dials make it FAR easier to evaluate exposure (and development, with film) than meters with LCD read-outs.
It is important to keep in mind that light meters (computer-evaluative meters in modern cameras are unpredictable) are designed to yield an exposure to render the metered area middle gray (Zone V). If the subject is light, you need to MAKE it light by giving more exposure than the meter suggests. This is called PLACING the subject on a higher Zone. Dark subjects are just the opposite.
In the illustration above, figures AA and CC were made automatically using the built-in meter in a Canon 5D MkII. The camera was set on Program Exposure and the meter set on Averaging. The background in figures AA and BB was a white card, and the egg in figures CC and DD was on a black card. Left to it’s own devices, the camera assumed the subjects were both gray and rendered them that way. Using Manual Exposure, I took a reading on the white card, PLACED it on Zone VII-2/3 knowing from my test (previous blog) that the card would then be rendered near-white, and the figurine would retain excellent detail. With the egg on the black card, my intent was to keep the egg from being overexposed, so I took a reading on the top of the egg and PLACED it on Zone VII-1/3, so I would be assured of recording some texture in the shell.
I have three spot meters: two Pentax Digital meters (these have analog dials) and a MeteredLight Pocket Spot. All three meters are matched to each other, so it doesn’t matter which I use.
The illustration above shows how a meter can help plan how to deal with subjects ranging from easy to extreme.
Figure A on the left shows a simple still-life with the spot reading’s EV values ranging from 10-2/3 on the brightest part of the glass, to 5 on the front face of the bowl. Just a bit under six stops range, and this fits my camera’s dynamic range almost perfectly.
Because I wanted to make sure the highlights were not burned out, I took the 10•• reading for the reflection and placed it just less than Zone VIII. Here is where I let the meter do the work for me. At a glance I can see my Exposure Index, an array of equivalent exposure settings, and how EV values fit in the scale from dark to light. This meter has a “window” that shows three stops above and below middle gray, so I can see the range from Zone II at the left and Zone VIII on the right. I turned the EV ring until the 10•• was positioned a bit below the Zone VIII extreme. All I had to do now was choose the particular exposure combo the meter rings displayed. On the top of the barrel I could see that one option would be 1/30 at f 3.2, but my lens wasn’t that fast, and I wanted more depth of field anyway, so following the exposures around the right side of the barrel, I could see that an equivalent exposure was ½” at f 13. Click!
Next I decided to work with a broader composition, so used a wider focal length to include a window scene along with the fruit. Figure B. The light had not changed, so using the same exposure as before, the tonalities of the bowl of fruit and surrounded areas recorded the same, but the window was completely blown out. The only way to deal with a scene like this is to use HDR techniques: make a number of exposures holding detail in the shadows and on up to the brightest high tones, then use a computer program to combine them. The ZS and a spot meter can take the guess work out of this, too.
Taking a reading on the front of the dark bowl, it still reads EV 5, so if I place that on Zone II I know it will have tonality. I see that an exposure to hold the shadows is still ½ at F 13. I now measured the brightest value outside the window and note that the sky measured EV 15. I want the sky to render well below near-white, so I’ll take that EV 15 and turn the EV ring so the 15 is placed just below Zone VII. I don’t want to change my f-stop, so I see that 1/80” will safely hold tonality in the sky.
So, a series of exposures ranging at least from ½” to 1/80” will hold all the tones in this extreme scene. Assembled in Photoshop CS5, the full range is held, figure C. This looks a bit dull because of the compression of such a wide range of tones, so figure D shows the combo with the mid-tones brightened up a bit.
Sadly, Pentax seems to no longer be making spot meters, though they can often be found on-line. So far as I know, the only spot meter still being made with an analog dial is the Metered Light Pocket Spot.( http://meteredlight.blogspot.com/ ) It is only 2×2-1/4” in size and has a ZS-ready dial, engraved from Zone I to Zone X. For the illustration, I put a couple of pieces of magenta tape over the scale, leaving a “window” equivalent to the scale of the Canon 5D.
I have had a lot of students with the do-everything Sekonic meter pictured above. It is a great meter, but a bit awkward to easily use the ZS. I made a simple little accessory card that makes it a lot easier to evaluate Zone placement and exposure. The example above shows a shadow exposure of 1/60 at f 5.6, and a highlight exposure of 1/60 at f 64. If I want to place the highlight on Zone VII-1/2, I put the VII-VIII on the card over the f64 mark and see that the reading under the Zone V on the card is f22-23, so that’s my exposure at 1/60”! I also see that my shadow now falls between Zone O and Zone I, so that area and subjects up to a stop or so brighter will not be recorded.
Bottom line. There are many reasons to avail yourself of the automated features in today’s sophisticated cameras. Computerized metering modes can work wonders in fast-changing lighting situations or if your subject is evenly lit and the sun is behind your shoulders. Autofocus can save the day with moving subjects, and auto-bracketing can help explore the nuance of exposure shifts. But if your camera is on a tripod or if you have a moment to reflect upon your subject, you may well find that with just a few seconds spent with spot meter and thought will give you more successful first-exposures than letting the camera make the decisions. It’s a snap!
P.S. In black-and-white, the “extreme” scene discussed above could be easily recorded with one exposure, on negative film. ;>)