Accurately comparing FF vs APS-C sensor performance? An open discussion.

Started Apr 8, 2013 | Discussions thread
OP VirtualMirage Veteran Member • Posts: 3,922
Re: Accurately comparing FF vs APS-C sensor performance? An open discussion.

Clayton1985 wrote:

First, I must say after going back and rereading my first post I noticed that all my spaces between paragraphs are missing.  I was typing it up in a different editor, copying and pasting it here.  In the DPR editor, my spaces looked intact, but I guess they didn't full translate once I posted.  So I apologize for the jumbled look, but it is too late to edit it.  Moving on...

"The relation of depth of field to focal length equivalents and their effects on required ISO when matching or exceeding shutter speed"

Yes, this explains that we are looking at specific scenario.  My numbers will be the same whether it was an F/2.8 or even a magical F/1.0.  The difference between the two will be the same and it will shift up and down the ISO range.  To keep the already long post as short as possible, I only picked a few ISO values.  If people are curious, I have all the values ranging from base ISO to peak ISO in a nice, pretty spreadsheet.  But I didn't see it necessary since the shift would be the same.  If people want to know what ISO 100 would look like, they can do the math with the information I provided.  Same goes if they want to know what ISO 6400 would look like.

The point was to be able to compare APS-C and Full Frame and to try and make it as apples to apples as possible.  Thus, we are only talking about ranges in which both the Full Frame and APS-C support.  If you start offering equivalent focal lengths that are only offered in Full Frame or APS-C, then we no longer have an accurate comparison.  We are now getting into to the territory in which only one camera can provide and you no longer have a comparison.

Your throwing examples at me at don't realistically exist in Full Frame fall into that category.  It would be the same if I threw back at you the opposite spectrum and asked if you had a 750mm F/4 equivalent lens on a Full Frame where as you do with the APS-C (the Sony 500mm F/4).  When it comes down to it, what were you trying to prove that had any relation to what the original discussion was about?

I'm not sure how I missed the point.   It seems like you presented your post as a discussion about the above but now only want to discuss the topic when it benefits APS-C.   It doesn't seem that productive to discuss only the advantages of APS-C because well....  hopefully, you would just buy an APS-C camera.  Discussing both the pros and cons of full frame and APS-C as it relates to your topic would be more productive (at least to me).

But you do seem to be missing the point.  I didn't discuss just the advantages of the APS-C.  If you read through my whole post, I mention the advantages of Full Frame and state that only in the worst cases will Full Frame look no better than APS-C.  I also mention that Full Frame holds the benefit of offering a shallower depth of field than APS-C for when that is desired, and that if you go with the shallower depth of field the Full Frame will be better than APS-C.  And Full Frame still holds an advantage at lower ISOs regardless of using a shallower depth of field or deeper depth of field to match the APS-C.  So I don't see it as discussion that favors only APS-C.

This wasn't intended to be a discussion about the range of focal lengths offered for each sensor.  It was intended to a be a focus on the sensor, the difference in depth of field when using identical focal length equivalents at identical apertures, and how ISO (and ultimately sensor noise) is affected if you wish to keep the depth of field and shutter speed the same due to the need to change the aperture.

Let me quote the last past of what I my post said, bolding certain parts to emphasize against your claim that I was only stating advantages of the APS-C:

"So what am I getting at here?

For one, you can't compare the performance capabilities of an APS-C versus Full Frame purely on its noise characteristics at said ISO.  Lenses, focal length equivalent, depth of field, aperture, and shutter speed all play a part in the final outputted image and at what quality.

Saying all that, my comparison still shows that there wouldn't be a disadvantage to going with a Full Frame.  Just in the worst case scenarios when trying to capture the pictures to identically match the look of an APS-C, it should look no worse than APS-C.  But it only goes up from there.  If you can afford a shallower depth of field or can afford a longer shutter speed, then the Full Frame will shine.  And at the extremely low end of the ISO range (ISO 50-100), the Full Frame is even better.  But also, maybe we aren't giving APS-C sensors enough credit?"

The title of your post was "Accurately comparing FF vs APS-C sensor performance?"  How would assuming that someone would want more depth of field be accurate?  IMO, an accurate discussion would cover the possibility of both scenarios.

Ok, maybe not the best title, but I am limited by length to do my best to accurately describe the topic in the fewest words possible.  What would you have called it?

I assumed that once you read the post you would realize there is more to it than what just the title is summarizing.  Once you read the post then you will see the added details and specificity I am looking at.  I think it becomes quite clear within the first few paragraphs.  But it requires you to read the whole post to fully understand.

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