cgardner
Offline
• • • • •
Upload & Sell: Off
|
@UK
I understand the point you make. There is glare off the gray card but I don't use the gray card for evaluating anything. I use the gray card for one thing, setting Custom WB, and when I do that I ensure it is angled and free from glare. The the context of the exposure phase of the workflow seen in that shot its role just mostly to hold the MacBeth chart and towels, which I usually hang over the card on a stand at subject position when setting lights for a portrait session.
I've used process control targets for years in my reproduction work and am well aware of why Macbeth makes their target out of matte construction paper vs. a more durable material. As you say to prevent glare when placed square to the camera in a test shot like this.
The overall lighting is what it is in that test shot because it is a test shot using natural light on a overcast day. The weather was crappy and I didn't want to go out in the yard and set up a stand so I just laid it on the porch and shot if from the front door. So don't assume that's typical usage. I seldom actually make a direct comparison of target to screen or print except when testing because I know by looks sight when it looks correct or not because I see it in every test shot I take in a wide variety of lighting conditions.
In any case I don't see any glare on the MacBeth target. The matte solid white patch has a .05 reflected density (90% reflection) correctly exposed at an eyedropper value of 250 in all channels. In the test shot it averages 246 in the JPG with the eyedropper tool; which while isn't dead center in the bullseye at 250 is still on it as far as I'm concerned as my capture baseline.
Again please try to understand this isn't a shot to evaluate lighting pattern but simply as a guide to first determining if the camera DR can handle the contrast of the lighting. My goal is to expose my RAW file about 1/3 stop below clipping in solid white objects like the white towel or .05 / 90% reflectance patch on the Macbeth target.
http://super.nova.org/TP/TargetNew_Step1.jpg
The white towel used with the clipping warning is like a radar detector in a car. It doesn't prevent me from speeding when I know I can get away with it (i.e. blowing some highlights) but using it and getting a warning makes me aware when and where I will be "speeding" and pay the fine of not having any highlight detail in the final steps of my total workflow.
Back in my zone system days I had situation awareness of scene range and how flat or cross lighting and overcast affected the same scene because I anal-retentively spot metered the scene with this 1° spot meter.
http://super.nova.org/TP/HoneywellSpotMeter.jpg
That photo would be how the meter was set after reading the EV value of the shadow detail at "3". The zone indication added to the meter was moved to put the 3 between Zone 0 (no detail black) and Zone 1(shadow with first detail revealed). Back then Adams had not assigned a Zone # to specular highlights and Zone 9 is were you would place a solid white object on the overall tonal range of the print. Later Adams added a Zone 10 (specular highlights white paper base of print) because of confusion about what a Zone 9 white was.
Zone 9 in metering a scene of a white car would be the part of the paint as it would appear without glare or modeling in flat light — a reflected density value of .05 log(100/90) due to the fact it reflected 90% of the incident light. That would not be the brightest white in the scene. Those would be in the specular reflections of the light on the white paint and chrome bumpers. With the spot meter it would be the non-specular white I would meter to determine scene range because it's the range WITH DETAIL I wanted to control.
The ZS was calibrated with testing so "normal" development time of the negative would fit a sunny cross-lit scene to a #2 print expose for black on the clear parts of a negative. For it to work as planned you first had to perfectly nail the exposure for the shadows perfectly to avoid loss of detail (the expose for the shadows part), then with testing find what film development time fit the highlights to the #2 print contrast range. That was done as below...
Put a subject in the direct sun. Expose for Zone 1 shadow detail. Shoot 4-5 sheets or rolls of film at that exposure. Develop the film for different times. Make prints from each exactly the same way, with print black set to the border of the negative..
http://super.nova.org/TP/ZS_Test.jpg
That's one my ZS tests from back '71 when I was learning how to use it. After making the four prints I laid them together for comparison. In person the differences are more obvious. As film development is increased the same exposure produces more density on the net. So in the test shots the shadows are all the same, but as the development time increased the highlights go from looking gray and underexposed to blown and overexposed. Somewhere in the middle there was a print where the highlights was perfect, and so was everything in middle. That became your "normal" development time (the develop of the highlights part of the B&W film paradigm).
What that meant in practical terms was that for any photo taken on a clear sunny day with B&W film if you simply zone metered the shadows and used the same development time as in the test you would have no trouble in the darkroom producing prints that looked every bit as good as the teacher's. That was after all the point of buying the books and learning the technique and was Adams became a legend — he simplified the process and make it simple for anyone to duplicate his results — IF THEY ACTUALLY UNDERSTOOD AND FOLLOWED HIS WORKFLOW.
Sunlight is consistent, so for example if EV3 correctly exposed the shadows, the brightness in the Zone 9 highlights in that sunny seen would also always have a consistent meter reading 8 f/stops brighter at EV11.
When out shooting with the tripod and medium format (in later years) after metering the shadows to set exposure I would find and meter a white object I wanted to render as solid white on the print, and note its EV reading. I knew a "normal" scene should read EV11. If the meter was anything other than EV11 it told me immediately out in the field that when I got back to the darkroom to make a full range print with perceptually correct looking highlights I had to do one of two things: 1) develop my film different than the "normal" time to fit #2 paper range, or; 3) use a different grade paper.
In actual practice I did both, depending on the situation. In college if going out with with tripod and fine grain film to shoot with the traditional ZS approach I did it exactly as Adams had in the 40's when he wrote the books, altering film development for each scene range photographed and printing everything on #2 paper. I was using a pair of Nikon Fs at the time, bought bulk film and loaded my own 10 exp. film cassettes so I didn't waste a lot of film.
For my PJ work for the student paper and other jobs I was able to get from the college I used the contemporary approach of only using one "normal" development time, then if the scene range wasn't a normal sunny day fit the negative's range to the print by using a different grade paper. By then Kodak had developed a paper called "Polycontrast" that changed contrast depending on whether the light in the enlarger was yellow or magenta. I still would spot meter the scene and take note of whether it had a "normal" baseline 8 stop Z1>Z9 range so when I got in the darkroom I knew how to filter the paper to match the negative. We had a little automatic tabletop processor in the darkroom (conveniently located in the basement of my dorm). When shooting on a deadline I could be hand the newspaper a finished print within an hour of shooting because there wasn't much trial and error in the workflow.
http://super.nova.org/TP/BW4.jpg
I didn't get a chance to set up my own darkroom again until the late '70s, after Zucker and working as a lab tech at Geographic and expanding my understanding of how to control tonal range with B&W using the methods I just described and color film by using key and fill to change the scene range to fit the fixed range of that medium. Although I didn't have any plans to make color prints at that point I bought a Bessler enlarger with an expensive color head for the convenience of being able to just dial in any yellow/magenta filter pack vs. using gel filters. That gave me better control of fitting negative to paper when using the normal development / polycontrast approach. Out of habit and SOP when working as a lab tech I documented everything I did and used control targets like the transparent step scales show below to measure the tonal ranges. DPReview uses a similar backlit transparent scale to measure camera DR:
When shooting on a deadline I could be hand the newspaper a finished print within an hour of shooting because there wasn't much trial and error in the workflow.
http://super.nova.org/TP/ZS_LabNotes.jpg
I still occasionally used the traditional ZS approach of bespoke development of the neg to fit #2 paper but most things I shot for my amusement where not that critical and Polycontrast approach was a easier way to achieve the same end goal, prints with full tonal range. My technical goal with digital is similar — prints and screen image with full tonal range — created as conveniently as possible.
When going to work for Zucker I connected the dots between why he used two flashes for color in a key over even fill configuration with my ZS experience in B&W. The contrast of color negs can't be adjusted by development because the film has three color layers. Both the film and print development is the same all the time. That means when a scene didn't fit the range of the color paper on a sunny day it was necessary to CHANGE THE SCENE CONTRAST WITH FLASH RATIO.
Outdoors in sun with color film you adjust the camera exposure is perceptually correct. What I mean by that is for a subject backlit by the sun you wound not expose to the right or left for highlight or shadow detail you would aim for the middle and get the faces looking correct. That would often blow the highlights and loose shadow detail but that was less important than the faces. That how setting exposure off a gray card or the palm of an outstretched hand came to be a common practice. The tone of an 18% gray card is similar to that of the average between the shadows and highlights on caucasian face. So if you took your Luna Pro and took reflective reading off the card or palm you by aiming for the middle you'd get the faces looking "normal".
That aim for the middle and get the faces normal approach also works quite well with digital, if you don't mind losing highlight and shadow detail. For example if you were to shoot a backlit subject in fully automated TTL metering your camera would bias the exposure in the same way average metering a card or making an incident reading with a Sekonic L-358 would if placed near the shaded side of the face and aimed at the lens. At ISO100 and 1/200th shutter speed the aperture setting would be f/4, plus or minus the influence of any bounced light hitting the front in addition to the sky light. The sky and any sunlit highlights on the subject's skin will be overexposed by 2 stops or more. If that's OK with you then that's the way you should roll. I prefer detail in my shadows so I do things differently...
http://super.nova.org/TP/TargetNewStep2.jpg
After setting the camera in M mode based on keeping the white towel entirely under clipping (for headroom in the entire workflow through JPG) I can look at the left side of the histogram and interpret what is trying to tell me. Here in this test shot for exposure it is telling me that the overcast light, while flat, is still exceeding the camera DR somewhat. In sunlight a backlit scene will have the histogram piled up more on the left as in this example:
http://super.nova.org/TP/DR_Backlight.jpg
At that point I have a decision to make. Do I want to leave exposure biased for perceptually correct highlights knowing it will not correctly render all darker tones, or do I want to change the camera settings and allow the highlights to clip to make the shaded side more "normal" looking? A can choose to do either one, but I find it is a more informed choice by first doing step one in my workflow — expose the highlights correctly (i.e. so they look normal).
Usually in a situation like that where correctly rendered foreground content is more important than correctly exposing the background I will: add dual flash to render the foreground with a full range and natural looking modeling....
http://super.nova.org/TP/HSS/_MG_5035.jpg
The if the underexpose background is a distraction isolate the foreground with cropping...
http://super.nova.org/TP/HSS/_MG_5035_Cropped.jpg
Is that a flash shot or one in sunlight? Most viewers without knowing the techniques used don't know the difference. My goal in a shot like that is make it looks similar to what would be perceived by eye without any obvious clues flash was used. The glare UK finds objectionable in the test card shot wasn't flash, but overcast natural light that was as diffuse as outdoor lighting gets. It looked the same way by eye in than orientation.
These ZS annotated flash shot illustrate that is "normal" in the highlights for exposure varies depending on the lighting scheme used. I don't set exposure via the target the adjust the lights, I adjust the lighting angles until the subject is rendered as I want it to be then use the target to guide scene range and exposure.
For example in this speedlight shot I adjusted the lights to eliminate any glare from the lenses of the eyeglasses, but knew there would be some on the metal frames but that was OK.
http://super.nova.org/TP/TowelGaryZS.jpg
Since all the lighting was in front I adjusted to make my key light create Zone 9 white on the towel and Zone 1tone in the shadows of the shirt. As with most things I know how to do that several ways manually and via ETTL but verify the results the same way:
1) Adjust overall exposure until towel clips then reduce it by 1/3 stop
2) Look at the shadows and make sure they have detail.
Key and overall exposure was set to render white highlights on front side Zone 9 white. In this studio shot I used back rim light and wanted to retain detail on the target ....
http://super.nova.org/TP/WhiteBGTowelCard1ZS.jpg
so when I put the subject in the same spot the white clothing will still have detail in the JPGs where the rim light hits it.
http://super.nova.org/TP/Ann/0470_Screen.jpg
The difference that someone like RDKirk who has used the zone system will grasp that perhaps others with less experience might not is that in the second shot with backlight the white objects on the front are not Zone 9 white as in the speedlight shot, but moved down one zone darker to Zone 8 to retain the perceptual ambience of the rim lighting while still managing to retain a full range of detail Zone 9 > Zone 1 in the overall print, with the only 255 values occuring in specular reflections and the only 0 values falling in deep voids where a detail would not be expected.
Because I started with the zone system I think in terms of zones, which are scene and print tonal values not f/stops of light measured in the scene as many today who never used it erroneously assume. My creative process starts by looking at the scene with my eyes and deciding what I want Zone 9 and Zone 1. It just so happens in most situations the reflectance of the black towel matches the reflectance of the darkest object in the scene an the white one matches the reflectance of the brightest one. So by putting just the two towels in the same light as the scene as proxies I can, with a few shots of the target, set lighting ratio to record the entire range with no loss of detail.
It makes exposing shots like this Chanel purse quick and very simple...
http://super.nova.org/TP/Chanel255.jpg
That's a type of shot where the detail in the white background isn't at all important but the specular reflections on the black surface are to model it's 3D shape and texture. That's a 2005 commemorative edition of the original design and the photograph is accurately reproducing the impression of the leather's texture by eye. There are a lot of different ways I could have adjusted ratio and exposure for that shot but I used the one described here and it only took about a minute and didn't involve a hand held meter. That's why I use the approach, it's quick and produces predictable results all the way to the final step of making a 900 x 600 pixel sharpened JPG.
Again it works for me. If you can't wrap your head around the concept and see it's merits that's fine. If you are too suborn to try it some time and help wrap your head around it that's fine too.
|
