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Author Topic: Histogram confusion  (Read 997 times)
KevinA
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« on: March 26, 2013, 04:24:10 AM »
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I'm not big on studying histograms at the taking stage, of late since I have been shooting with the 1D X I've found them somewhat confusing in post.
I can shoot a scene at a good average exposure, I can asses the image and think bringing up the shadows would help or if possible getting a bit more out of the highlights.
The histogram for the highlights looks to be well within reach, I can bring the exposure down to see where it ends, the thing is despite the histogram showing I can get the detail well within the exposure, the actual image still shows clipped extreme highlights.
I've never seen this with previous cameras.
This is just a histogram question I have no complaints regarding image quality of the X which i think is superb.
I'm just confused by the histogram showing all highlight detail is captured but plainly it is not.
Any ideas?
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Kevin.
KevinA
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« Reply #1 on: March 26, 2013, 04:56:11 AM »
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Shooting raw of course.
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Kevin.
scooby70
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« Reply #2 on: March 26, 2013, 05:03:50 AM »
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I haven't got an explanation for you but I just wanted to say that you're not going mad or doing something wrong - I've seen that too in cases where there's a small amount of extreme highlight and to prevent blinking highlights in the shot I've had to back it off much further than looking at the histogram would have me believe was required.

To be honest and I may be wrong but I just assumed that the small percentage area of the image that these extreme highlights represented was too small to register on the histogram.
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FranciscoDisilvestro
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« Reply #3 on: March 26, 2013, 05:06:43 AM »
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Which tools (software) are you using? Are you checking the raw histogram with RawDigger or something similar? It could also be a bad camera profile
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KevinA
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« Reply #4 on: March 26, 2013, 05:11:45 AM »
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Which tools (software) are you using? Are you checking the raw histogram with RawDigger or something similar? It could also be a bad camera profile
Aperture and Photoshop, no time to add yet another step into the workflow:-)
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FranciscoDisilvestro
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« Reply #5 on: March 26, 2013, 05:34:01 AM »
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Does it happen if you perform the RAW conversion in ACR? It is somewhat difficult to tell without an actual raw file or at least looking at a real RAW histogram (such as in RawDigger)

Regards
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Ellis Vener
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« Reply #6 on: March 26, 2013, 09:23:05 AM »
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When are you seeing the clipping? On the camera, in Aperture? or after opening the photo in Photoshop as a TIFF, PSD or JPEG?

If the latter is the case which color space are you assigning for post-raw processing?

When you say "extreme highlights"  could those be specular highlights  - light sources in the photo  or reflections of light sources in the photo?

Is is possible you've got some areas that are beyond the range of your histogram?
« Last Edit: March 26, 2013, 09:25:48 AM by Ellis Vener » Logged

Ellis Vener
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stamper
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« Reply #7 on: March 26, 2013, 09:55:07 AM »
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I have found from experience that when I use the histogram in camera and the information is just touching the far right then in reality there is still about 2/3 of a stop between the camera and LR. The histogram in camera is a jpeg rendering of the raw and it is about 2/3 underexposed as compared to LR .Google for UNI white balance and you will find an explanation for this.
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Ellis Vener
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« Reply #8 on: March 26, 2013, 04:24:59 PM »
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Some histogram basics: http://www.ppmag.com/web-exclusives/2007/12/what-is-a-histogram-and-how-do.html
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Ellis Vener
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KevinA
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« Reply #9 on: March 27, 2013, 04:48:42 AM »
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When are you seeing the clipping? On the camera, in Aperture? or after opening the photo in Photoshop as a TIFF, PSD or JPEG?

If the latter is the case which color space are you assigning for post-raw processing?

When you say "extreme highlights"  could those be specular highlights  - light sources in the photo  or reflections of light sources in the photo?

Is is possible you've got some areas that are beyond the range of your histogram?
In Aperture, I'm using Adobe 1998 colour space. Not specular, mostly clouds or white buildings in full Sun.
I've not done any formal testing on this, I usually see it in white clouds. It's more a curiosity than serious problem.
I've never had it with other cameras, I'm usually deciding where exactly i'm prepared to clip the highlight as the histogram extends further.
Not the X, I often get a histogram that fits , if I just used the histogram I would often be bringing in the shadows and highlights points to the ends of the h/gram.
As I say more a curiosity than a problem as I go by eye anyway, the h/gram is just another guide.
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KevinA
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« Reply #10 on: March 27, 2013, 05:18:20 AM »
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OK I've looked a bit deeper, it looks to be an Aperture issue, camera raw does show the histogram extends beyond  range.
It's only noticeable in dusk shots with a setting Sun in. Aperture says you have all the highlights captured, camera raw shows a more truthful representation.
The end result is the same.
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Kevin.
stamper
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« Reply #11 on: March 27, 2013, 05:59:19 AM »
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The problem with comparing different raw converters is that their "default" settings are different. The initial renderings will not be zerod out. In reality you can't start of with a neutral setting but you can try and make them as neutral as possible by removing any contrast setting and any sharpness setting. Applying sharpening will affect the rendering.
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