Home Products Download Order Contacts

adobe.photoshop.camera.raw

Subject: Exposure to the right and tone placement



In another popular thread there has been much discussion about proper exposure of digital images. There appears to be consensus that one should place the highlights to the right so as to make best use of the 2048 levels supposedly available in the brightest f-stop of a 12 bit image.

In an interesting post, Rags Gardner disputes the common wisdom of 2048 levels in the brightest f-stop (go to technology, tones n zones in the link below).



I can't follow some of his argument, but it is evident that just because the analog to digital converter has a bit depth of 12 does not mean that all of these tones will be available; the highest tone will be the point at which the sensor saturates. Beyond saturation, the values will be clipped.

For my D70 camera I determined the clipping point by exposing a Kodak step wedge in half stop increments from a gray card reading and found that clipping occurs at about 1 stop above the gray card reading (since the Nikon meter is calibrated for 12% reflectance, proper exposure would be the gray card reading plus 0.5 EV). This is illustrated by this image, which has been converted from raw to 16 bit linear space by Dave Coffin's DCRaw. Note that the two brightest tones are no longer differentiated.



The brightest reproducible tone occurs at a 12 bit data value of 3900, which corresponds to 243, 31266, and 62533 respectively in 8 bit, Adobe 15+1, and 16 bit encoding. Since clipping occurs with only one half stop overexposure, one should not excessively expose to the right. In the Kodak chart, M corresponds to the midtones; note that there are more steps available below than above the midtones and slight underexposure would preserve more tone values at the expense of greater noise in the shadows. With this particular camera, one should not attempt to place the highlight at 4095 in the 12 bit linear raw file (255 in 8 bit).

If the subject contains only mid-tones and no light tones, exposing to the right will distort the tone values when the gamma correction is applied as shown in Rag's example of a photograph of a black person, unless negative exposure compensation is used in ACR to place the midtones where they should be.

Now that the pixel mafia is back from their meeting, I hope they will add their insight and expertise to the discussion. BTW, I did find that highlight recovery in ACR did a remarkable job of recovering the clipped highlights.

Reply


View All Messages in adobe.photoshop.camera.raw

path:


Replies:
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement
Re: Exposure to the right and tone placement

Copyright 2006 WatermarkFactory.com. All Rights Reserved.