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

Started Apr 8, 2013 | Discussions thread
VirtualMirage
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Re: Accurately comparing FF vs APS-C sensor performance? An open discussion.
In reply to Tom Wilson 62, Apr 9, 2013

Tom Wilson 62 wrote:

Hallo VM, I agree with your narrative as it stands (although I don't agree that a large sensor gives you less depth of field than a smaller sensor as it's more the focal length that does) but, it reminds me of my more youthful days when I used both medium format and 35 mm cameras and, in those far-off days, it was often said that for quality you couldn't beat a larger negative.

Where I'm coming from is that a FF image needs much less enlarging than an APS-C for e.g. an 8x10 and thus shows less noise (thus higher quality?) at a particular ISO setting.  Also, you're correct that depth of field is less but, unless you frequently need extensive DOF, it often doesn't matter.

I like your comments and they made me think but, as an old available light fanatic, I love my A99 (and thinner DOF on people pics) while still enjoying the reach with zooms on my A65.

Take care.  Tom

Hello Tom,

Out of the other posters so far, I think you have come the closest to understanding what I was initially writing about.  Thanks! 

If you want to be more technical about it, it is true that it isn't the sensor itself that attributes to the depth of field itself, but more so of the focal length.  But you can't have one without the other, and it just so happens one sensor uses a smaller portion of the same focal length, giving off a different equivalent focal length.  Hence why it is usually referred to as the sensor size being the cause for depth of field difference.  It isn't correct in the truest sense, but it goes hand in hand.

Because of this, the view through a 50mm on one sensor does not give the same view as it does on another.  This is why we can't, or at least shouldn't, compare two different sized sensors using the same lens but instead should use ones that offer comparable equivalent focal lengths.  But when you do this, you change the depth of field, which in turn affects the aperture you may want to use.

And yes, the Full Frame does offer the advantage of thinner depths of fields that would be more of a challenge with APS-C sensors.  When that is needed, or desired, there is no comparison to the advantages it can bring.

Thanks again.

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Paul

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