# Help with interpreting histogram.

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/

### Dear Sir:

Dear Sir:

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

### Thank you.  But, I'd really

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???

### Dear Sir:

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.

### Just thought of this: How

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

### Dear Sir:

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).

### Been quite a while since I

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?

### Dear Sir:

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.

### Interesting as I never

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.

### Dear Sir:

Dear Sir:

I meant raising ISO during shooting.