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Author Topic: Light Metering  (Read 7802 times)
howard smith
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« Reply #20 on: February 15, 2005, 02:01:26 PM »
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I thought the problem was likely solvable, and it appears it is in Photoshop.  A similar process to processing film to adjust the negative to the print using the Zone System?

The point was that increasing the dynamic range of a digital camera to 12 stops would not represent an alternative to correct exposure any more than 12 stops of B&W eleminates exposure problems.  It provides more latitude to get acceptable results, but not a fix.  Variable contrast printing paers can cover up some exposure/developing problem, but not fix them.

To get the results you expect, there seems to be little alternative to correct exposure
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Ray
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« Reply #21 on: February 18, 2005, 08:32:06 PM »
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The full range of b&w film (black to white) is about 10 stops per Ansel Adams.  Some can get a bit more or less.  The dynamic range is about 8 stops, and the textural range about 6 stops.  The dynamic range of printing papers is about 5 or a little more stops - less than film.

This 6 stop textural range is the true limit for me, from my digital darkroom perspective. Turning texture into black or white is easy in PS. Bringing out and enhancing texture where none exists is impossible.

An image with a true textural range of 10 stops would look very flat, but would be very useful. Correct exposure would then be considered the exposure necessary to capture the 10 stop range, if it existed in the scene. I'm sure such a camera's evaluative metering system could handle that. Correct exposure every time  Smiley .

If the scene being photographed was a low contrast scene, say 5 textural stops, there might be a slight issue of 'correct' exposure, but more likely it would be an issue of 'ideal' exposure. Would expose to the right still be an advantage? Possibly not. The trade-off of slower shutter speed against marginally less noise might make it a non-issue.

I can't help wondering if b&w film in Ansel Adams' days had had a textural range of 10 stops, would Adams have devised the Zone system?
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Ray
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« Reply #22 on: February 21, 2005, 07:51:24 AM »
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Ray, I would suggest that if that white house is as white as the paper it's printed on, and you wanted to see details, you did something wrong.

Howard,
I frequently do something wrong when taking photos. Often one simply doesn't have the time to get everything right before pressing that shutter. The changing light conditions wait for no-one.

I'm reminded of the circumstances of one of the most famous photos of the 20th century, Moonrise over Hernandez.

The car screeched to a stop. Ansel didn't have time to search for his light meter; didn't even have time to remove the strong yellow filter which increased exposure and contrast in a scene that was already of greater contrast than the range of the film.  

Apparently, he visually estimated the moon, pale white with grey details, as having a Zone Vll value, which would require 1/250th at f8, then decided to give it 2 stops more, 1/60th at f8. After adjustments for the filter and a greater f stop for greater DoF, he used 1 sec at f32 which is slightly longer than 1/60th at f8.

He didn't have time to take a second shot. It's ironic that Ansel Adams' most famous photo proved to be the most difficult negative to work with and a shot that had been taken on the spur of the moment without the use of a light meter and with an irrelevant and unwanted filter attached to the lens.
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howard smith
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« Reply #23 on: February 22, 2005, 09:09:22 AM »
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"It looks like I was spot on when I hinted that maybe you are a bit stuck in the old ways   ."

I wouldn't say "stuck."  Stuck to me means you want to move and can't.  Part of the pleasure I get from photography is doing it myself instead of a lot of automatic and computerized things I have no control over or even a real chance of understanding what the equipment is doing "for me."

Actually Ray, I do use Photoshop and even have the some of the basic skills need to add some snap.  But I just don't understand why you think a 12 stop dynamic range will solve exposure problems.
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howard smith
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« Reply #24 on: February 23, 2005, 10:38:46 AM »
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Thanks.  I get frustrated and sorry when I see so many new cameras with more and more auto features.  Many users forget or worse, never knew, what all the auto camera is doing for them.  No need to focus.  No need to understand exposure, especially with auto bracketing.  DEP (or whatever it is) does all the depth of field stuff for you, so no need to learn anything here.

Then Photoshop fixes all the mistakes.  No need to look at the composition - I can move mountains in Photoshop.  Don't pick up trash or position the camera to exclude an ugly, clone it out.

But I rant.
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Ray
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« Reply #25 on: February 24, 2005, 07:28:41 PM »
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Howardbatt,
I like to think my jests always have an element of truth.

The concept I'm trying to convey here is this. The mechanical aspects of handling the camera, getting the exposure to correspond with some sort of zone system, the struggle to overcome the limitations of the camera in respect of dynamic range, precise calculations of CoCs in the field for DoF purposes etc etc etc, can be distractions from the contemplation of artistic matters whilst in the field, gazing at the view.

Time spent with a measuring tape to accurately get the distance between camera and tree for DoF purposes is time that perhaps could be better spent looking for a more advantageous angle from which to take the photo, for example.

Given that at any site one is going to spend a limited amount of time, what do you want to spend your time doing? Thinking in terms of composition, perspective, shooting position, changing lighting, play of light and shadow and so on, or stuffing around with a whole lot of mechanical adjustments to a contraption that's either antiquated or limited in its scope and flexibility?

Given the choice, which would you prefer?
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howard smith
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« Reply #26 on: February 25, 2005, 08:27:51 AM »
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Ray, photography as you define it sounds pretty mechanical, impersonal and sanitary to me.  Something done equally well by a surveillance camera in a parking garage, a spy satellite, or a robot on Mars, as a real person.  If you could squeeze the smell of hypo in the morning in there somewhere, we would be closer.
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Jonathan Ratzlaff
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« Reply #27 on: February 03, 2005, 10:49:01 PM »
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If you had a camera without a meter and no way to evaluate your exposure, I would suggest an incident meter.  However, given the quality of the in camera metering now and the ability to evaluate your image, you don't need it.  At one time I would have suggested it if you were doing a lot of studio flash, however you don't need it there either.  Why use numbers when you can see the result.
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howardbatt
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« Reply #28 on: February 05, 2005, 08:03:11 AM »
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Thanks, Dinarius.  That, essentially, is what the articles to which I referred said.  Those articles took it beyond studio, as well, with one saying incident reading is essential for landscape photography to accurately measure shadow and highlight.  Another wrote that color is dramatically better when measuring incident light.  His reasoning was that reflected light meters measure everything as 18% grey.  His examples were of a white dinner plate with fruit, a grey plate and a black plate.  All appeared as slightly different shades of grey in the examples he said resulted from measuring reflected light.

My problem is that which I implied with the idea B & H wouldn't be selling them if no one really needs a meter.  Obviously it is people who have the greatest knowledge who are going to spend more than $500 on such a device so I wondered what I was missing.  After all - the light meter doesn't change the photons striking my camera's sensor.  I understand the difference between incident and reflected metering but I don't understand why bracketing, for example, (with not just three exposures but five or ten) won't yield the same results.  I DO see why the meter would be absolutely critical if I were using film - there would be no way to know it worked until the film was developed and then it likely would be too late.
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howardbatt
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« Reply #29 on: February 06, 2005, 11:42:50 AM »
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Dinarius, I'd surely like to see some of your work if you have a web site.  You've obviously been doing this for years professionally while I've been doing it haphazardly for enjoyment.  Now that I'm old and I have a good camera and have some time, I decided to study the art and techniques.  Hand in hand with that decision and the decision to get the EOS 20D comes what some close to me (you know who I mean) calls the "tech toy bug ."  That's what led me to hand held meters and to salivating over Sekonic's high tech offerings.  

With my very limited background in the technical aspect of photography, I simply could not understand why a separate (from that which is in-camera) meter would have any use at all in digital photography.  Not because photography has changed along with the change from "celluloid to digital" but because I can take a hundred shots at 1/3 intervals and choose from them. Not only that, I use PhotoImpact 10 and it has the ability to blend three or four or five different exposures to dramatically expand the tonal range of the result.  So, if I bracket with five exposures, I've increased the tonal range of the result pretty dramatically.

On the other hand, such an approach is nothing more than me being the button pusher for the computer - I'm the robot who enables the machine.  And - picking the best of the lot doesn't necessarily mean any of them are really "good" - there is just one which is "more good" or "less bad."  That's when I got intrigued with the picture of the WHITE (not from Ireland) fox on the snow.  It has some color in the guard hairs but basically, it's white on white.  I doubt bracketing would be the way to make the picture - at least it would take a LOT of bracketing to be lucky enough to get the right one.  And THAT'S why I thought incident metering would be the way to go - not just that it's faster than bracketing or averaging - but that it gives the technical data needed for the technical camera to make the art that I see and want to capture.

And that's my argument with those who say nay to the expensive meter (but her eyes glaze over) and I'm sticking to it.

I tried to read Ansel Adams and also a book by a professor of photography who undertook to "bring it up to date."   Unfortunately, MY eyes glazed over.  I've read enough about the zone system to appreciate how it fits into all photography but the rest is so technical I gave up in favor of my ultra-modern camera.  Heck - I'm not even smart enough to figure out how to properly use a modern flash like the Canon 580EX.  So I do it like I used to and then explain that what people are looking at is not bad exposure but, rather, my artistic interpretation of the scene.  Add a little scowl as I say that and I get away with it.

Howard
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Jonathan Wienke
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« Reply #30 on: February 15, 2005, 01:33:49 PM »
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Dynamic range is easy to decrease, especially in Photoshop. Increasing it when clipping has already occurred is the difficult problem. Give me a camera with 12 stops of DR, and I'll be more than happy to do levels and curves and local contrast enhancement to add some snap to the print.
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howard smith
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« Reply #31 on: February 11, 2005, 04:33:01 PM »
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Two thoughts.  First, when I entered Brooks Institute, every student was required to have a 4x5 view camera and an incident light meter.  Because many assignments were in the studio with flash or hot lights, a flash meter was almost essential.

Second, I am not sure that "expose to the right" is the essence of the Zone System.  It is my understanding that "expose to the right" provides the maximum exposure that does not clip the highlights.  However, there are instances when clipping or blowing highlights might be desirable.  Such an instance is large specular highlights, such as direct sun or flash on water, snow, ice, metal, glass, etc.  Without clipping or blowing out the very brightest part of the image, the remainder of the image would be underexposed.  Isn't the correct exposure the one that shows a desired white with texture as white with texture?
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fangel
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« Reply #32 on: February 20, 2005, 03:00:04 AM »
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That's the general idea, devise a way to gradually decrease the photodetector's sensitivity to light as the charge level increases, so that the electron well will never quite fill completely (at least from light exposure, dark current would be another issue entirely), and response curve between light exposure and output voltage going to the ADC will more closely match that of the human eye. That will increase dynamic range that can be built into a photodetector well of any given size.
On some of Sony´s professonal studio tv-cameras you can adjust the response curve (gamma function) and you can also selectively alter the response in the highlight region (dynamic knee function). Perhaps these functions would be beneficial on a dslr.

best regards

Tom
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howard smith
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« Reply #33 on: February 21, 2005, 06:27:17 AM »
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Ray, I would suggest that if that white house is as white as the paper it's printed on, and you wanted to see details, you did something wrong.

In the Zone System, you would select a dark part of the image and meter it to show the detail and tone you want.  Then meter the house.  Expose for the dark part, and develope until the highlight came up as desired too.

You only get two areas as you want, the rest will fall where it may.
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Eric Myrvaagnes
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« Reply #34 on: February 22, 2005, 10:11:29 AM »
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This dicussion is giving me a sense of "deja-vue all over again" from many years ago, when dinosaurs roamed the earth and cameras still used film. Some manufacturer actually marketed (briefly) a film aimed directly at photographers like Ray. I think the maker was FR, but I'm not sure, and I can't remember the name of the film. But it was a B&W 35mm film that had three different emulsions on it, one with a very low ISO rating (or probably ASA, before ISO), one with a medium speed, and one very high speed (say, ISO 800 or 1600). The idea was pretty much that any exposure would work and you'd never get blown highlights. A little like stitching three exposures together in PS.

The film didn't stay on the market very long.  

Eric
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-Eric Myrvaagnes

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howardbatt
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« Reply #35 on: February 23, 2005, 11:02:22 AM »
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Gee - it's nice to see a dinosaur here. My first "real" camera was an Argus C-3.  I left the Hawkeye crowd in the dust with that and a $9.00 light meter.

But - I'll never go back.  What I like so much about digital is that I can take 100's of pictures and not so much as think of what it's going to take in dollars or time to process them.  Not so I have hundreds to choose from but because I just enjoy taking the shot.  Sometimes I'm pleasantly surprised by what develops.  Most times I click "erase" - but (after paying for the camera and the CF card) it cost me nothing.  

Isn't it nice that even with all the high tech and automation that people still hope to emulate Ansel Adams?  I admire Clyde Butcher even more than Ansel Adams - here's a guy who should probably cut back on the cheeseburgers who hauls a HUGE view camera and an equally HUGE tripod into the Everglades, sets up in water up to his waist and takes pictures of trees and flowers and clouds while the gators are cheering him on and the bugs are happy he eats so much.  Oh - it's all black and white and admired by a lot of people.  He's an artist and is recognized as such.  Of course, he's also a dinosaur.
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howard smith
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« Reply #36 on: February 24, 2005, 09:51:58 AM »
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I have from time to time stood in almost the same places Adams put his tripod and made an image.  Hernandez being but one.

I recall once while hiking coming upon a nice place to rest.  I looked at the partically frozen lake.  I had a strange feeling I had been there before, but I knew I hadn't.  Then I realized I was looking at Adams' "Frozen Lake and Cliffs, Sierra Nevada, California."  While quite similar, not at all like the b&w print I had seen.  And I could of course see a lot of stuff that had been cropped from Adams' image.  I took out my camera and took a photo, a kinda "I was there" thing.  My color slide looked very little like Adams' image except for some shapes here and there.  But for the memory of Adams' image, Howard the Artist would have taken a rest, admired the view, and walked on.  I have no vision and my Nikon had even less.
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Ray
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« Reply #37 on: February 25, 2005, 08:48:42 AM »
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I was trying to be brief, Howard. I don't have any nostalgia for the smell of darkroom chemicals which I understand are rather unhealthy anyway. I much prefer sitting in front of a computer, and capturing the moment can involve quite a lot of preparation as you well know, such as hiking for days through the rainforest, or booking airline tickets and arranging accommodation in Italy, where I hope to capture many, many moments during the next few weeks  Smiley .
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Terry G
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« Reply #38 on: February 04, 2005, 01:11:15 PM »
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I bought myself a Sekonic 504 to use with my Mamiya RZ a while back and became quite attatched to it - a great meter. It`s more or less gathering dust these days, which I feel is a shame (can`t bring myself to part with it though) but I have found on occasion (if I remember to pack it!) that its easier to use the sekonic to take a few spot readings (to check crucial highlights mainly) than pan the camera around the scene when I`ve already composed things carefully in the viewfinder.

 I`ve got to say though that if I didn`t already have the sekonic, I dont think I`d be in any hurry to go out and buy one now, happy as I am with my in-camera metering,

regards T.
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Dinarius
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« Reply #39 on: February 06, 2005, 10:58:59 AM »
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Howard,

The incident meter "assumes" that everything in the photograph is 18% grey and reads accordingly.

The reflected meter "converts" everything to 18% grey.

Correct?

So, it's question of priorities. What are you trying to achieve in a given photograph?

With the fox in the snow, a spot meter reading of the fox will give you a pretty good exposure, without any bracketing, because the fox's coat ( I am assuming an orange/red fox of the type we have here in Ireland AND that the sun is behind you.) is as near as dammit to 18% grey.

On the other hand, the (far easier to take) spot reading of the static snow will give you an exposure about two stops underexposed, since the rendering of textured snow is about two stops above 18% grey. So, you will need to adjust the reading accordingly.

But, an incident reading of the scene will immediately give you a working exposure which, given the assumed dominance of the snow within the scene, you can tweak accordingly. i.e. bracket -1/3, for example.

As to your example of the shadows: well, how important are they to the overall image? In bright mid-day sunlight, with the sun directly behind you, a "normal" ( and I use the word advisedly) exposure for ISO 64 is 1/250 sec. @ f 8/11. Now, let's say you take a spot reading of the shadows in the scene and they are five stops below. Will they hold? Probably not. Are they important enough to overexpose the rest of the scene a little? That's up to you.

You have to prioritize what you are seeing.

I don't think you're missing anything! ;-)

D.

ps. Have you read Ansel Adam's "The Negative"? It's all there! ;-)
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