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

Started Apr 8, 2013 | Discussions thread
VirtualMirage
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Re: You misunderstand
In reply to OldClicker, Apr 10, 2013

OldClicker wrote:

Exactly and "appears"= perception.

There is more than one definition of appears and I think you are interpreting it as the wrong one:

This is how I am using it:

  1. To be or come in sight, to show up.

This is how it seems you are using it:

  1. To have an outward aspect, similar to seem.

Now let's look at perception:

  1. A results of perceiving (observation) or a mental image (concept).
  2. Awareness of the elements of environment through physical sensation (sight, sound, taste, feel).

Let's look at perceives:

  1. To become aware of through the senses.
  2. To attain awareness or understanding of.

Perception is not the same as the former definition of appears, but I can see how you may try and relate perception if you are thinking of the latter definition.

But if you don't see it that way, then we will just have to agree to disagree.

If DoF was just perception, then wouldn't the amount of DoF perceived change from person to person despite all the constants above being the same?

Since perception is based on an individual's experience, that means that it could appear differently to someone else.

You can build a model by making assumptions about the size of the image, the distance viewed, the person's eyes, the light in the room, etc. (as DoF calculators do), but the actual DoF does change with all of these.

When viewing an image captured by a camera and lens, a person's eyes have no direct effect on the DoF.  The lens on the camera is the eye, it's ability to change the aperture is what affects the DoF.  The viewer's eyes or even the photographer's eyes have no effect on the actual depth of field being captured in the image.  The only things the eyes do is allow you to determine whether the camera's current settings are producing too much or too little depth of field based on what you are perceiving, and thus change the camera's aperture settings so that the depth of field looks close to what your are perception of the shot should look like.

Light in the room doesn't play a factor in DoF.  It can be bright as the sun or pitch black and DoF will still be the same so long as the lens parameters don't change.  What will change is length of exposure.  But length of exposure doesn't affect DoF.  If I expose for 1/1000 of a second or for 100 seconds, DoF will be the same.  But you will usually change the aperture setting and ISO speed to shorten or lengthen this exposure time.  By changing the aperture, then you will be changing the DoF.

This doesn't mean that your comparisons using such a model are wrong as long as the underlying assumptions are correct for the discussion.  However if your model assumes that the pixel density/number of pixels has no affect on the, "measureable range in which an object appears sharp", and it actually does, then the model is wrong.

Pixel density doesn't affect DoF, it only makes it more or less noticeable in the final image.  It doesn't change the amount of DoF there is in the image.

If pixel density affected DoF, wouldn't you think that all the current DoF calculators would have an option to factor that?

At least the ones I have seen don't.  What plays a factor is sensor size, focal length, equivalent focal length, and aperture.

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Paul

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