DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
Ian Stuart Forsyth
OP Ian Stuart Forsyth Veteran Member • Posts: 3,377
Re: U R Slippery II

awaldram wrote:

moving_comfort wrote:

By the way, can you explain how you changed your story on this answer you gave below?


You changed your story on that, which represents progress - what made you change?

As I said earlier I'm bored with this now but have to pull you up on that miss quoting

you said

you I used to hold the position it does not (change DoF when displayed at same size)

I did do and always will do , Ian posted examples that prove it , I posted examples that prove it, and both James and myself posted algorithms that prove it.

No amount of trying to make something different will alter that.!

DoF is relative to magnification.

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

A lens does not change any of it characteristics ever !

Altering Focal length aperture etc as you change format to produce a similar image and then stating it is equivalent is based on the idea the larger format is superior to the smaller.

Often it is not often the smaller format has higher pixel density , lower relative noise, more efficient pixels or better DR this then completely breaks you equivalence.

take a 6mp FF and a k5 run you 'equivalent ideas to create ti 'equivalent pictures.

Only they wont be the FF will be noisey and grainy

How come ?

take these to images as I asked before both shot from an external light meter reading why are

A very simple question, at the single photocell level why does the K 5 pixel show up as bright as a Q pixel when both are shot at the same shutter speed, Fstop and iso when viewed on the back of the camera. We know that the k5 photocell is several times large than the Q’s giving the k5 photocell more light whereas the Q’s is smaller and would receive less light. This should make k5 image way brighter as it has captured more light right?

  1. The photocell of the Q is several times more efficient at gather light so it would show up as bright
  2. That all sensor have a gain applied to them to bring them up to the same brightness to meet the standard iso rating and make up for the smaller photon count of a smaller photocell
  3. Physics is out the window
  4. Size of the photocell has nothing to do with how much light is gathered

they the same exposure ?

In your La La world the first image should be over 2 stops under exposed as F2.8 on the Q is f16 on aps-C !

do you see the error in your thinking yet?

You can approximate DoF or FoV but to then assume those approximations are some kind of equivalent across all parameters leads to your La La worlds and is easily disproved as the images below.


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