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Author Topic: Perfect Exposure for Raw Histogram  (Read 3910 times)
CBBN
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« on: January 16, 2006, 11:39:53 AM »
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It's understood that exposing to the right, just short of blowing out the highlights, maximizes the capture and minimizes the noise in the shadows.  And the RAW histogram in Camera Raw is a better determiner of exposure than the JPEG histogram on the back of the camera.  So if I'm going to shoot a stack of several hundred historic prints in RAW, with a tethered laptop, what's the best subject matter to shoot to determine that ONE exposure that I'm going to use?  The Macbeth color checker (8.5 x 11") or should I just choose one great print that has a range from shadow to highlight?  The lighting will be nailed down on a copystand (tunsgten).  

Chris
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61Dynamic
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« Reply #1 on: January 16, 2006, 12:11:13 PM »
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The color chart would work best as you only need to worry about the white square not over exposing for ETR.

Then, an additional benefit to that is that once you have the Raw on your computer, you can correct the exposure for all of the images based off of the final shot of the CC. Just set an sample point on the white square and drop the exposure slider until the point reads about 238-242. That will get exposure set dead-on for all of the images.
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Jonathan Ratzlaff
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« Reply #2 on: January 18, 2006, 09:27:03 PM »
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Wouldn't you want pure white to be at the very top of the histogram?  That is paper white?  Wouldn't the rest of the tones fall into place somewhere in the scale.  Given the dyamic range of a reflective print, you are probably going to have all kinds of space at the bottom of the histogram as the brightness range of a reflective image is quite low compare to
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Anon E. Mouse
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« Reply #3 on: January 18, 2006, 10:13:00 PM »
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A gray/grey card. That should be good for the reference exposure. You camera should handle the contrast range of a prints, which can be around 30:1. In contrast, an average outdoor scene has a contrast range of 160:1.

I would also include a grey scale in each frame for post processing. If you are shooting color prints, I would shoot a MacBeth color checker for reference color for processing and output, but a Kodak gray scale also has color indices which can work as well with the added benefit that you may be able to include it in each frame.
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CBBN
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« Reply #4 on: January 19, 2006, 11:29:02 AM »
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OK, I'm back from the test shoot.  I used the 8.5 x 11" MacBeth chart to set my exposure, keeping the white patch at about 240 in Camera Raw.  Then I used the 2nd patch (very light gray) to white balance the tungsten lights (still in CR) which worked perfectly.  I did a few prints (b&w and color) with these settings and they looked very good, in the usual Camera Raw flat-kinda-look, processed them staying in 16bit.  I finished the 60 or so shots, batch processed them, and the resulting TIFFs look quite good.  A simple levels adjustment layer brings the contrast and tonality where I want it.  The originals were all over the place, B&W & color, from 8x10's down to 120 contact prints.  The majority of the color was actually 4x6 prints, but when those prints were very good, the resulting copy shots were very good.
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bjanes
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« Reply #5 on: January 21, 2006, 10:39:08 AM »
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It's understood that exposing to the right, just short of blowing out the highlights, maximizes the capture and minimizes the noise in the shadows.  And the RAW histogram in Camera Raw is a better determiner of exposure than the JPEG histogram on the back of the camera.  So if I'm going to shoot a stack of several hundred historic prints in RAW, with a tethered laptop, what's the best subject matter to shoot to determine that ONE exposure that I'm going to use?  The Macbeth color checker (8.5 x 11") or should I just choose one great print that has a range from shadow to highlight?  The lighting will be nailed down on a copystand (tunsgten). 

Chris
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Wouldn't a good flatbed scanner be better for this purpose, presuming that the originals are not framed?

Bill Janes
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CBBN
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« Reply #6 on: January 21, 2006, 10:58:32 AM »
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Wouldn't a good flatbed scanner be better for this purpose, presuming that the originals are not framed?

Bill Janes
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The problem with scanning is time.  I'm going to have 3 days to copy hundreds of photographs, and each photograph has a caption on the back which is needed as well.  At 2 minutes per scan per side we'd get back logged by noon.  I'll have 2 or 3 researchers pulling prints (at the National Archives, NARA) faster than I could scan them.

NARA does allow scanning though.

I did a comparison of a WWII B&W print with excellent tones that I scanned with a flatbed (a much better Epson than probably could bring to DC) vs. a copy shot with a Nikon D1x (RAW capture) and a Canon 1DsMkII.  All printed at their default 300 ppi size, and then all printed at 22" wide (the width of the book we're producing) after interpolating them up w/Bicubic Smoother.  The 1DsMkII was certainly sharper than the Nikon (17mp vs. 5 mp) and the flatbed was almost as good...  For THIS particular workflow, the camera won out.

Also, I'm not sure if flatbeds can scan RAW, and the 12bit capture might give an additional tonal edge.

Chris
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61Dynamic
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« Reply #7 on: January 21, 2006, 11:30:49 AM »
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What's the name of the book you're making?
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bob mccarthy
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« Reply #8 on: January 21, 2006, 11:52:23 AM »
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Copying doesn't have a significant dynamic range. Nothing like outdoors with a bright object (zone 8-9) in direct sunlight and a dark object in shadow (Zone 1-2) where you may want detail in both.

Copying under lights will be easily accomplished within the range of the dlsr sensor. I'd not run right up against the edge of the histogram (255) and leave a little bit of headroom. All other adjustment can be done in photoshop.

bob
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bjanes
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« Reply #9 on: January 21, 2006, 02:26:26 PM »
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The problem with scanning is time.  I'm going to have 3 days to copy hundreds of photographs, and each photograph has a caption on the back which is needed as well.

Also, I'm not sure if flatbeds can scan RAW, and the 12bit capture might give an additional tonal edge.

Chris
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Yes, speed and portability as well as making use of equipment on hand can be the determining factors in  equipment selection.

As far as RAW, there is no need for it with a scanner, since they sample all three colors per pixel and there is no need to demosaic the image. The better scanners have 16 bits per channel, but I don't know if this would make much difference for reflective originals.

Good luck with your project

Bill
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CBBN
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« Reply #10 on: January 21, 2006, 10:05:28 PM »
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What's the name of the book you're making?
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The working title at this point is The Illustrated Encyclopedia of the Vietnam War.
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