# DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
Re: U R Slippery II
1

moving_comfort wrote:

awaldram wrote:

Equivalence as defined by you ,Ian and Lumo is just wrong and misleading.

A lens does not change any of it characteristics ever !

The above leaves me wondering what you've learned....

I've learnt I shouldn't have included Falk in the above it not his fault you misinterpret his words.

Interesting conclusion you make .... Me learned something when I haven't altered my position.

Having established that

a f2.8 lens is always and f2.8 lens irrelevant of format

ISO is standardized across cameras so exposures remain constant (I mean der!!)

and

DoF is a function of magnification and not lens or sensor, once a circle of confusion is established that does not define the final perceived DoF

I'm not sure what you think I've learnt that I wasn't saying 3 months ago ?

I think this thread has run it's course, but I suspect we'll revisit this subject, maybe after everything has had a chance to germinate.

Let me leave you with Falks comments maybe you missed it

As you say, the real beauty of the equivalence theoreme is that as soon as any of the three properties "depth of field", "image noise", "diffraction" becomes equal in two images (for a given field of view, shutter speed, camera position, focus distance, focus direction, number pixels and brightest pixel normalized to 100%), the other two properties do automatically become equal too (holds true w/o the neglegible magnification aporoximation too).

which is what I've been saying all along

F2.8 - f2.8

iso 100 = iso100

etc etc

http://www.josephjamesphotography.com/equivalence/#quick

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens).

So I still think you and Ian were trying to prove something based on using half of proven theories mixed up with a bit of voodoo maybe because you don't understand them or maybe because your driving a hidden agenda .

Every-time you try and change internationally recognized standards such as ISO. aperture and imply they magically change if you change format I will crying foul!!

You can't chuck 150 years of photographic know how down the toilet without being caught out !

So I've repeatedly said a lens does not alter dependent on sensor you have repeatedly said it does, in fact your whole argument was built on this fallacy.

Not with what 8 reputable source all quoted in this thread say (and I'll repeat)

Neither the focal length nor the f-ratio of a lens change as a function of sensor (for example, a 50mm f/1.4 lens is a 50mm f/1.4 lens, regardless of the sensor behind the lens).

All that left for you to-do is admit you were wrong !

Honestly it wont hurt that much , you've run-out of wiggle space time to man up.

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