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

Started Apr 8, 2013 | Discussions thread
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 Re: Nonsense In reply to VirtualMirage, Apr 14, 2013

VirtualMirage wrote:

Klipsen wrote:

Practice what you preachÂ

We are all guilty.  Just some more than others.

Nah, just you.

That's the pot calling the kettle Black.

It is easy to label much of anything that, especially in these forums.

You don't get clean by washing yourself in other people's dirt.

That one statement when looked upon just by itself can be considered that.  But when you put together everything else that it is based around, then not so much.  I am the one that is being accused of fabrication, which is not the case.  I am not calling them a liar or someone that is making stuff up, only one that is stuck looking at a small portion of the bigger picture.  A part of the picture which I feel is not valid in my original observation.

There's nothing wrong with your comparative test of the two formats ... except that you try to use a strict mathematical formula with fixed values for the CoC of different sensor sizes - and when people tell you this cannot be done, because there are so many variables, not least the CoC itself, you get up in arms and write endlessly long posts with the sole purpose of saying that no matter how wrong you are, you're still right.

No, DoF is not a mathematical formula - you only use formulas to get an approximate idea of what the DoF will be. The mere fact that the CoC is an arbitrary value means you cannot claim to have a patent on the truth about DoF.

How granular do you want to get?

Meaning what?

We might as well then throw this in along with the circumference of a circle and pi.

Now, that's utter nonsense. You need to shorten pi, because there's an infinite number of decimals, but you can only round it off, not choose your own value (3 is an easy number for mental calculations if you can live with a 5 % error margin (or add half one tenth for more precision). Other than that, it's not a measure, but a factor - and it's not user defined.

At some point you have to determine where to stop counting and just round to the nearest number so as to finally get to the point while still remaining valid.

That has little (in fact nothing) to do with the CoC, which is user defined - although there is a general acceptance of values around 0.03 mm for 24x36 mm sensors.

They can! There is no fixed value for the CoC.

There may not be a fixed value, but ...

No ifs and buts. You try to make strict rules where there are none. If part of a picture is out of focus, no mathematical formula can force it to be sharp in the eyes of the beholder.

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Ceterum censeo soleam calidam ISO esse delendam.

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