Help with interpreting histogram.

flycaster's picture
Submitted by flycaster on Fri, 01/22/2021 - 11:08
Forums: 
General discussion

I am trying to use the histograms to determine which raws to process, but I am having some trouble interpreting the histograms. The link below will bring you to three images with differing histos.  What I find problematic is how to interpret the tail-offs to the right in the histos. I've labeled these images according to their tail-offs to the right. I believe that the "just right" labeled image would be the one to process, but I'm not sure.  So, I'd appreciate just how to look at the histos in order to choose the "editable" one. Thanks.
Long tail-off

Short tail-off

Just right?

https://www.flickr.com/photos/187947376@N03/50863462527/in/dateposted-public/
 

LibRaw

Fri, 01/22/2021 - 11:29

Dear Sir:

The lightest one is indeed the one to use (given ISO setting is the same).

flycaster's picture

flycaster

Fri, 01/22/2021 - 14:23

Thank you.  But, I'd really want to know the meaning of the "long" and "short" tail-offs.  I know that neither indicates any blow outs, but that's about it???

LibRaw

Fri, 01/22/2021 - 14:54

Dear Sir:

For base ISO the length of the zero flat to the right indicates the amount of stops the exposure could be increased. For non-base ISO, add log2(current_ISO / base_ISO) to that value.

flycaster's picture

flycaster

Sat, 01/23/2021 - 08:57

Just thought of this: How would one then choose a RAW image if the ISO's are different?

LibRaw

Sat, 01/23/2021 - 10:44

Dear Sir:

Usually the first criteria for choosing the shot in this case is exposure: the higher is the exposure, the less noisy the image looks. Between two shots with the same exposure the shot taken at higher ISO often looks less noisy (but watch for highlight clipping).

flycaster's picture

flycaster

Fri, 01/22/2021 - 16:50

Been quite a while since I delt with logs, nonetheless, let's see if I get this right. When one gets histo tail-offs, this indicates that one can try to move the things to the right to get a better exposure?  Thus, when the histo ends at the right, that indicates all is good?

LibRaw

Fri, 01/22/2021 - 18:23

Dear Sir:

Yes, that's the essense of it; however while choosing tools to move histogram to the right raising ISO is the last choice.

flycaster's picture

flycaster

Sat, 01/23/2021 - 08:54

Interesting as I never thought of raising ISO as a means to control exposure when doing post. I guess I naively was doing something right.

LibRaw

Sat, 01/23/2021 - 10:40

Dear Sir:

I meant raising ISO during shooting.

Add new comment