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Author Topic: Light Metering  (Read 8012 times)
Eric Myrvaagnes
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« Reply #60 on: February 04, 2005, 03:56:24 PM »
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When I read your replies and remembered that Ansel Adams probably didn't use a $300 - $600 digital light meter - I felt a lot better.

And remember: Edward Weston hated using any meter at all.
 
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-Eric Myrvaagnes

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Dinarius
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« Reply #61 on: February 06, 2005, 07:32:49 AM »
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But with landscape photography it's difficult to measure the incident light on the subject since it's far away.
Not sure what your point is here.

There is only one sun and it's 93m miles away. So, even if you did walk the five miles, or whatever, to take an incident reading, it should be exactly the same as the reading taken next to the camera.

Landscape photography involves a single and extremely distant light source. Hence the need for either; a. an incident reading and some bracketing or, b. spot metering if the dynamic range is of importance to you, as in for example, the Zone System.

Studio photography usually involves more than one realtively close light source. Even when only one light source is involved, it relatively close proximity to the subject requires careful monitoring. Spot metering may do the trick, but indident readings are far easier. Also, on a purely "best practice" point, any unnecessary removal of the camera from the security of the tripod is welcome in my view. I'm much happier to drop or knock my lightmeter! ;-)

D.
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Jonathan Wienke
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« Reply #62 on: February 06, 2005, 12:41:18 PM »
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The big fallacy of using an incident meter for landscape work is that the light falling on the subject is not necessarily the same as the light in the vicinity of the photographer. Ever heard of a partly cloudy day? Some days you can get away with that assumption, but other days it would be totally foolish.

Determining optimal digital exposure isn't really that difficult to figure out; non-specular highlights should be exposed just below the clipping point. If the DR of the subject is beyond the capture DR of the sensor, you'll have to make some tough choices regarding how much of the highlights to blow vs shadows to block, or else bracket.

Digital Exposure And Metering Strategies
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Graham Welland
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« Reply #63 on: February 12, 2005, 02:20:08 PM »
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ok, so I should have been a little more careful about the 'expose the right' comment ... my point was that you're shifting the available brightness range to fit the digital cameras capabilities and its the act of actually DOING THE SHIFT that is similar.

I totally understand the goals of the zone system to place the required brightness/tones exactly where you want them by adjusting the exposure. If that means blowing highlights or blocking up shadows then so be it.
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Graham
howard smith
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« Reply #64 on: February 17, 2005, 08:44:08 AM »
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Ray, I could be totally wrong but a stop is a stop.  The difference in expsoure between Zones 2 and 3 is a factor of 2, same as between Zones 9 and 10.  So the darker 6 stops have a range of 64X, same as the brighter 6 stops.

I'm confused.  Are you suggesting the lower portion of the scale be logarithmic and the upper portion be linear?
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Ray
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« Reply #65 on: February 18, 2005, 05:43:11 AM »
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Howard,
As I see it, the whole raison d'etre of the zone system devised by Adams and Archer is due to the inadequacy of film to capture the dynamic range of reality. It's claimed that the DR of B&W film is around 11 stops. But what does this mean? Certainly not 11 stops of high quality detail.

A description of each zone from 0 to 10 (available through any Google search) is quite illuminating. Zones 0 and 10 are complete black and complete white devoid of any detail. Zone 1 has so little detail it's as good as black. Zone 2 has some detail that might be useful. Zone 3 has pretty much full detail, but not of the highest quality. Zones 4 to 6 (one stop below to one stop above 18% grey) have the highest quality detail. Zones 7 & 8 have reasonable detail beginning to decline. Zone 9 has the barest hint of detail.

Seems to me, what we have here are 3 stops of full, high quality detail, or 6 stops (zones 3-8) of reasonably good detail. Depending on your standards, a film that can capture these 11 zones could be described as having a dynamic range of 6, 8 or 11 stops. Whatever standard you use to describe the DR, reality (a sunny day with a few shadows) will have a DR at least 4 stops more.

I recall Michael mentioned a while ago that you need 10 stops of DR to capture full detail in a bright, contrasty scene. That's 10 stops by the same standard that would describe B&W film as having a DR of 6 stops.

If we ever get an imaging device capable of a true DR of 10 stops, then there'll rarely be an issue of overexposing or using a zone system to shift the exposure a stop or two above or below that for 18% grey. Whatever you point the camera at will be recorded in full detail, both highlights and shadows.

The balance of those shadows and highlights in the processed image and print can later be determined according to taste, in the more comfortable and relaxed environment of the digital darkroom  Smiley .
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Ray
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« Reply #66 on: February 20, 2005, 10:03:15 PM »
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Ray, give any film no exposure, and you get pure black. Opn the camera up long enough and any fim will be pure white, regardless of dynamic range.

True! But underexpose such a film with a 10 stop textural range in order to create a pure black, and a white shirt will look like a grey shirt. In order to get the shirt looking white on the print you'd have to (1) increase the development time of the negative, thus losing even more detail in the shadows, and/or (2) use a high contrast paper, again losing yet more detail in the shadows.

There would seem to be little purpose in doing this because you would be cutting off your options for future processing from such a negative. The best approach would be; no zone system; one correct exposure every time which would include full detail in all areas of the image; perhaps some alteration to development time if an assessment were made that no available grade of paper could produce the desired result and if dodging and burning were going to be too much of a hassle because of the nature of the scene.

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Notice that Adams said the "full range" of film was 11 stops (not 10 as I said before) from black to white (Zones 0 thru X). He used all 11 stops, not just the 7 stops of texture (Zones II thru VIII).

The 10 stop film with full texture would have around 15 zones from black to white (the full range of the film) by the same reasoning and niether Adams nor anyone else would be able to use the 15 zones except in rare circumstances. The descriptions of the zones would then be something like, zone 0 black but rarely seen; zones 1 & 2 partial detail but rarely seen; zone 3 full detail; zone 15 pure white but rarely seen; zones 14 & 13 partial detail but rarely seen; zone 12 full detail.

I think I've got that right. Had to edit it twice.

Sorry to appear so contentious. I just get the impression you are perhaps stuck a bit in the old ways .
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Ray
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« Reply #67 on: February 22, 2005, 12:32:45 AM »
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Ray, I think you are getting beyond anything that I understand. Are you talking about a camera that will essentially automatically digitally blend several images?

Many digitally blended images exhibit more shadow detail and highlight detail than a single image. But, in my opinion, they start looking flat with washed out looking shadows and muddy looking highlights.
Howard,
It looks like I was spot on when I hinted that maybe you are a bit stuck in the old ways  Smiley .

I really have little idea what methods would be employed if we ever do get a high DR camera that can tackle reality without compromise. Jonanthan made a good attempt with a design for a leaky photosite, but that's getting into areas beyond my understanding, too.

I think it's unavoidable that such a wide DR image is going to look flat in its RAW state and this might well be a disincentive for manufacturers to to develop such a sensor.

Even at the current stage of development, we have examples of people who migrate from a P&S camera to a 20D and complain that the images look flat. They're used to snappy, high contrast images with slightly blown white shirts and black shadows that have to be black because the alternative is sheer noise.

I get the impression that you don't use Photoshop. If you did, you'd realise how easy it is to make a flat image snappy, or anything else.
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Ray
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« Reply #68 on: February 22, 2005, 10:00:47 PM »
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Howard,
I very rarely come across pure blacks. To be pedantic, I think never. The shadows in the folds of a black velvet suit would be about the closest you would get to it. Ordinary black suits are really charcoal. I've got parts of the interior of my studio painted in matte black. It's not really black but it's the blackest paint I could find.

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Or are you saying that if you had a very large dynamic range, you wouldn't care if you lost a zone or three by messing up the exposure?

Not quite. A wide dynamic range is not a guarantee against making stupid mistakes, but if you do, it's sure going to help.

I'm basically saying, with modern camera technology and a really wide dynamic range, the type of automatic, evaluative exposure metering that modern Canon cameras boast would work every time. You could then place your 'pure' blacks, if desired, either through a click on an automatic process in PS such as 'auto levels' or 'auto contrast' or be more creative and actively select what parts of the image you think would look best as pure black or near black, or whatever.

If Ansel Adams had had such a camera at Hernandez, he would have had time to remove that inappropriate yellow filter and take a second shot, and that would not have been the most difficult negative he'd had to deal with  Cheesy .
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Ray
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« Reply #69 on: February 23, 2005, 10:51:32 PM »
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Sure the camera is a mechanical device - but so are paint brushes (when compared to fingers, that is).
That's a good analogy. I'd like the camera to be an extension of my fingers as a panit brush is to a painter. No fussing with an external meter and the possibility of blown highlights or intractable shadows. No worrying about flashing histograms and decisions to autobracket or not. I just take the shot and the pre-visualisation takes the form of what I can do with it in Photoshop later.

This, I would suggest, frees me up to concentrate on purely artisitc matters whilst on the job.  Smiley
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howard smith
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« Reply #70 on: February 28, 2005, 12:51:28 PM »
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Ray, I didn't intend to single just you out for shooting style.  We do differ there quite a bit though.

There is a thread going now about "missed opportunities."  I look at missed photos about the same as missed stock market moments.  I would be richer than Bill Gates if I had ... .  But I'm not because I didn't ... .  I might be a world famous photographer if I had ..., but I didn't ... .  I don't worry or fret over missed photo moments.  Like buses, there will be another one by in a few minutes.
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howard smith
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« Reply #71 on: February 04, 2005, 06:22:02 PM »
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The best photographer I know uses a rangefinder camera with no meter.  He doesn't carry a meter either.

My cameras of choice have no built-in meters.  I used reflective handhelds for years, then was forced to use an incident meter at school.  I would never go back.  

I still use a spot meter from time to time.  I also use Polaroid film once in a while to check exposure and composition before the "real shot."

One problem I have with many camera meters is the user has no real way of determining wht it is doing.  They average this and that, weight soem readings, on and on.  When I use the handheld meter, the exposure may be wrong, but it is the one I selected.
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howardbatt
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« Reply #72 on: February 07, 2005, 09:02:43 AM »
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Thanks very much, Jonathan - especially for the link. I spent some time wandering around your site. It's very impressive. I especially liked the more "candid" yet very professional wedding portraits. The people are relaxed and "caught" but nothing about the portraits makes them look like snapshots. Well lit, well composed and nicely exposed.

I had pretty well convinced myself that an incident meter would help me but I've now realized it won't because I don't have the skills - yet - to use it effectively. That kind of technology is much like high end computers and photoshop CS. Many people buy them thinking the technology will make them better without working - just like diet pills that work in your sleep require no effort.

So - I thank everyone who took the time to write. What came through loud and clear is that there are as many ways to enjoy this art as their are practitioners. I don't think there's a "right" or a "wrong" way - it's all subjective. So, as I get better (which I will measure by compliments) I will know what kinds of tools I should have to stretch my own envelope a little more.

Beautiful pictures - thanks for the site. And the insight.

Howard Batt
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Ray
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« Reply #73 on: February 16, 2005, 07:29:36 PM »
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But latitude doesn't always make an effective substitute for correct exposure of the original.
Well, certainly not with film. Even with relatively high DR B&W film, the shadows might well be unsatisfactory if the exposure has been for the sky or the moon. I suppose it really depends on the degree of latitude, the nature of the automatic, evaluative in-camera meter and the design of the imaging chip that could capture a 12 stop DR.

This concept of 'expose to the right' was not widely publicised when DSLRs first arrived on the scene. If I've understood the situation correctly, there's an imbalance and wastage of levels due to the linearity of the imaging chip and the eye's different sensitivity to varying intensities of light. In other words, the camera does not produce enough values in the darker regions but produces too many in the brighter regions, ie. more than the eye can discern in the brighter regions.

From the camera's perspective, just a 1 stop increase in exposure requires the sensor to capture double the number of photons. If we consider current DSLRs to have a DR of 7 stops, then to design a camera along the same lines to have a 12 stop DR would seem to be impossible. The sensor of such a camera would have to be able to capture 32x the number of photons of a full-well current DSLR.

Without dramatically increasing the size of the sensor, an alternative approach would be along lines suggested by Jonathan in another thread; ie. progressively compress the values in the brighter parts of the image so that the total number of values in the brighter 6 stops would be closer to the number of values in the darker 6 stops, instead of 64x greater.
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howard smith
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« Reply #74 on: February 18, 2005, 08:02:42 AM »
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The Zone System's raison d'etre is not the inadeqaute dynamic range of b&w film, but that the film's dynamic range is much greater than the printing paper.

Pure black and pure white provide useful information - there is nothing there needed to be seen, or the area is really dark or bright.  Pure black is not low quailty detail.  It could be perfect.  A dark shadow area of black velvet reall is black with no detail.  Even brightly lit black velvet is pretty much deatil free - black with soem texture.

"The balance of those shadows and highlights in the processed image and print can later be determined according to taste, in the more comfortable and relaxed environment of the digital darkroom."  Zone System users, including Adams, frequently do/did this in the wet darkroom.  They take the same image several times and "fiddle" with the processing one image at a time until they either run out of images or get what they want.  I guess with digital, one never runs out of images.  But with film at least, once the film is exposed, there is little if anything that can be done with the dark areas.  

Enter bracketing exposure.  The problem with film at least is bracketed exposures with several examples of each exposure for several trial developings equals a lot of film for one image.  The subject may not stand still that long, or the photographer may not carry that much film.

Enter experience and previsualization.  The need to bracket exposure goes down and the number of "fiddles" goes down.
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dlashier
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« Reply #75 on: February 06, 2005, 06:25:14 AM »
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>  one saying incident reading is essential for landscape photography to accurately measure shadow and highlight.

But with landscape photography it's difficult to measure the incident light on the subject since it's far away.  imo an incident meter might make sense for studio work or copy work but the camera's spot meter more than meets the needs for outdoor photography in most cases and even can "make do" in the studio. The spot meter will let you evaluate the dynamic range of the shot and help you choose the tradeoff between shadows and highlights with minimum experimentation or bracketing.

- DL
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howard smith
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« Reply #76 on: February 20, 2005, 04:27:30 PM »
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Ray, give any film no exposure, and you get pure black. Opn the camera up long enough and any fim will be pure white, regardless of dynamic range.

Notice that Adams said the "full range" of film was 11 stops  (not 10 as I said before) from black to white (Zones 0 thru X). He used all 11 stops, not just the 7 stops of texture (Zones II thru VIII).
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howard smith
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« Reply #77 on: February 21, 2005, 09:57:38 AM »
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Ray, I think you are getting beyond anything that I understand.  Are you talking about a camera that will essentially automatically digitally blend several images?

Many digitally blended images exhibit more shadow detail and highlight detail than a single image.  But, in my opinion, they start looking flat with washed out looking shadows and muddy looking highlights.
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howard smith
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« Reply #78 on: February 23, 2005, 07:47:16 AM »
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Ray, I suppose that if I had a camera with a very very large dynamic range, I could select out of an image the stops I want, adjust them in Photoshop to fit them on paper, and print. Until then, I guess I am just stuck with having to accurately meter and expose. (To me, that is an interesting and challenging part of the puzzle. Actually, if I wanted truely great images everytime, I would take all the money I spend making my own and buy the Master's.)

Then along comes Epson with a Super Dynamic Range printer/paper combo and I want a camera with another 6 stops of dynamic range.

Seems that if the dynamic range of the camera is made large enough, there would be no real need for a meter any more. Write a Photoshop plugin called Focus-all, and you have the ultimate in point and shoot cameras. You might be approaching the elimination of the need for a photographer if you mount this bad boy on your robot that knows a great image when it sees it.

Yes, I am frustrated.

If Adams hadn't lost his light meter, maybe he would also have had a better time, although it would be hard to imagine just how much better it could have gotten.  One of the beauties to me of the Hernandez image is that it was difficult for a master, and that not just anyone with a $50K Canon could have done the same thing easier.  Maybe Adams enjoyed the challenge also, having to quickly recognize the potential, draw on his knowledge and then work hard in the darkroom to coax out the latent image to look like the image in his head.
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howardbatt
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« Reply #79 on: February 23, 2005, 10:11:00 PM »
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Thanks for the tip, Ray, but I'll probably just keep puttering with the camera.  Sure the camera is a mechanical device - but so are paint brushes (when compared to fingers, that is).

You're not the first to tell me I make no sense and I'm sure you won't be the last.  But I do appreciate your taking the time to set me straight even though you say you don't know what I'm talking about.

You and I disagree completely about the purpose of a camera but that likely is because we put it to different uses.  However, I'll not try to persuade you to my way of thinking and will understand completely if you simply ignore me should I feel the urge to write something again.
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