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03-24-2008, 11:05 AM   #16
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Hmmm - I've learned so far not always to trust my K10d histogram or the pic on a 2.5inch screen

I have taken a number of pics side by side by just using the histogram as the only measure of the perfect exposure e.g took pic at default exposure and histogram was far left and the pic looked very dark on display - gave the pic +0.7 ev to have the histogram kind of having a good overall "hill" in the middle.

When viewing on my 17" monitor - I went with the pic that I assumed was underexposed (based on histogram) and found the +0.7 ev compensation too washed out.

So be wary by just judging the histogram (well with the Pentax anyway)

D

03-24-2008, 11:14 AM   #17
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The article in the 1st post of this new thread is very useful, basically saying that the LCD & histogram are only a guide and not reliable - the data they use is based on the jpg processed data and not the actual Raw data captured.

https://www.pentaxforums.com/forums/general-pentax-photography/23538-exposing-raw.html

IMHO if you want to be 100% sure bracket your shots either manually or using auto

Simon
03-24-2008, 03:42 PM   #18
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QuoteOriginally posted by simonkit Quote
The article in the 1st post of this new thread is very useful, basically saying that the LCD & histogram are only a guide and not reliable
Basically, it says the histogram is a gamma-corrected 8Bit histogram which is different from a photo editor's 8Bit histogram. However, the article applies to a Canon 5D.

The posts in this thread (including my own) express a significant level of confusion among posters. Lot of misleading information. I'm booked for an investigation

Maybe I add to say this much: Don't try to get a "hill" into the middle. Try to get the histogram edges equal distance apart from the borders, or if impossible, to get equal amounts of clipping on both borders.
03-24-2008, 05:27 PM   #19
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QuoteOriginally posted by falconeye Quote
Well, I understand everything about a histogram in a photo editor.
A photo editor histogram is the so-called images's N-Bit Histogram and has a linear scale, where the f-stop scale is logarithmic. There are no "middle parts" behaving differently.

I see two choices:
  1. The sensor doesn't capture luminosity linearly (a bad thing to be compensated by tone mapping -- so one should know about).
  2. The Pentax back LCD histogram isn't a photo editor's 8-Bit histogram.

I will investigate this and report my findings as soon as I have them. Thanks for the responses so far.

You need to take a close look, and plot in 'stops" not FStops i.e. 1, 2, 3...

if you do this you will see the histogram is linear over about 5 stops in raw, with compression at both ends.

If you want to go by "F-Stops", then of course beause the F stop is a log scale, it is not linear, but if you just count in stops or EV , then for an extended portion of the middle range the histogram is perfectly linear with each stop. DO the test and see for your self

03-25-2008, 04:19 AM   #20
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QuoteOriginally posted by Lowell Goudge Quote
If you want to go by "F-Stops"
I should avoid the term fstop then. For me, 1 fstop = 1 EV w/o the absolute meaning of EV. So, in all my previous posts, replace fstop by EV. Thanks for hinting me at it.

BTW, EV is a logarithmic scale by definition, too, look at the formula here:
Exposure value - Wikipedia, the free encyclopedia
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