DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
awaldram Forum Pro • Posts: 13,214
Re: DOF and Cropping take 2

moving_comfort wrote:

Ian Stuart Forsyth wrote:

continued from the post above

Just a highlight key points I would like to address

red is Ian

Green is GossCTP

and Black awaldram

But I see it as equivalent please see below

Do you really believe this website above , I mean really ?

How accurate is the information they provide ?


That Cambridge Tutorials page is not very accurate, and that site has been debunked in the Nikon fora before.

Some folks are just not careful with their googling, and they still try to source it, adding to their confusion

About the author of Cambridge in colour.

"As part of the Cambridge University Photographic Society, I conducted student workshops relating to general camera and digital SLR technique, photographic post-processing and low-light photography. These included participants ranging from those with their first camera, to more seasoned users wishing to refine their techniques. Time permitting,"

Well you could always sign up for a workshop and tell him he and everyone in the world doesn't know what he's talking about


As you can see that it calculates the same equivalent of lens and F stop as I had calc’d

Here is a quote from the site

“As sensor size increases, the depth of field will decrease for a given aperture (when filling the frame with a subject of the same size and distance). This is because larger sensors require one to get closer to their subject, or to use a longer focal length in order to fill the frame with that subject. This means that one has to use progressively smaller aperture sizes in order to maintain the same depth of field on larger sensors. The following calculator predicts the required aperture and focal length in order to achieve the same depth of field (while maintaining perspective).

As an example calculation, if one wanted to reproduce the same perspective and depth of field on a full frame sensor as that attained using a 10 mm lens at f/11 on a camera with a 1.6X crop factor, one would need to use a 16 mm lens and an aperture of roughly f/18. Alternatively, if one used a 50 mm f/1.4 lens on a full frame sensor, this would produce a depth of field so shallow it would require an aperture of 0.9 on a camera with a 1.6X crop factor — not possible with consumer lenses!”

And a reminder that whether you crop an image in the camera or in post with PS you are altering the size of the format, just as many do with a D7100 or a D800 in camera or during post

Now which site do I believe yours or mine?

Yours is of course correct.

mm lets try another 'wrong source'

Most photographers accept the common belief that short focal length lenses have greater depth of field than do long lenses. A wide angle lens, in other words, will give greater depth of field than will a telephoto. Right?

Sounds about right, but it's not the case. In fact, if the subject image size remains the same, then at any given aperture all lenses will give the same depth of field.

Has the super Nikon Fora debunked that one as well because I have many more thousands even , en-fact every body who has bothered to work it out besides it seems the Nikon Fora


-- hide signature --

Here are a few of my favorite things...

This is so obvious to me I'm astounded you fail to see the error in your opinion and even more attempt to ridicule those who do.

whether you use common sense or indeed apply the algorithms given above you will hit the right answer so how could you be so wrong for so long ?

Unless you change both the CoC and Focal length then for any constant image size DoF remains constant ..... simpulz.!

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