# DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
Re: So, your conclusion is that 'equivalency = false'?

awaldram wrote:

moving_comfort wrote:

awaldram wrote:

moving_comfort wrote:

awaldram wrote:

As far as I;m concerned both you and Ian have had ample proof of the error of your (and only your) crackpot theories.

So, everyone who understands and discusses equivalence - like Falk Lumo, Joseph James, etc and everyone viewing this thread who understands it are crackpots?

I think I'll invite Mr James to this thread - head crackpot, in your view - he probably likes a good laugh as much as anyone.

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So I'm done here you obviously can't even understand the maths that prove your wrong are unable to see the truth in images posted by both Ian and Myself

Ian and yourself? Don't you know Ian's trying his best to make you see the light?

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because of your FF centric world , you have no objectivity, even when so obviously wrong to everyone you eventually reach the point your becoming a bit of a joke.

Equivalency is not tied to "FF", it applies between every existing format size. It applies just as much between Q and 645D as it does between aps-c and FF. Don't try to make this a 'FF good, aps-c bad' argument. It simply describes a relationship, and in practice can describe a lens/sensor combo that might work better for someone than another lens/sensor combo. That's it. Don't take it so personally, it's an equation.

An equation that proves your wrong , as has been posted by James .

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Really? Can you show me where James showed how equivalence proved me wrong?I think he'd be as suprised to hear that he did that as me

(I think you're attributing some of what he was writing incorrectly, by the way - but I'll let him speak for himself.)

I'm sure James is completely aware what is formula shows and the relationship to view size , Magnification , Focal length and sensor size.

But I can do better how about Bob Atkins ?

I'm sure some people will say, OK, but what if you don't take angle of view into account. What's the relative DOF if you use the SAME lens on a small-sensor camera and a full-frame camera?

Now you run into the problem of what you are comparing to what. The same lens on the two formats will give you different fields of view, so if you enlarge each image to the same size (say 8x12), you won't have the same print so you really can't compare DOFs. If you crop the 35mm negative to give you the same print as the digital image the answer is easy. The DOF in the cropped 35mm print and digital image print will be exactly the same. You're using the same lens and same size image (cropped 35mm or digital), so you get exactly the same DOF.

Oh dear chalk up another source that agrees with me, almost using the same words I did.

This is funny, crop the Full Frame 35mm negative to give you the same print and what do we get a ASPC negative and we a surpassed that they have the same DOF for the same FOV. I hope you are not showing this a proof that FF at F/2.8 is the same as APSC at F/2.8. Donâ€™t you see the irony for FF to have the same dof you have to alters the FOV of the FF . Would this not tell us that DOF is relative to the format being used at a given FL and Fstop?

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