# DOF and Cropping take 2

Started 10 months ago | Discussions thread
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 Re: DOF and Cropping take 2 In reply to awaldram, 10 months ago

awaldram wrote:

Ian Stuart Forsyth wrote:

http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm

Its kind of funny as Cambridge Tutorials has got this right and even their calculator is correct as this is what I used who would have thunk EH

Yep they seem to know what there talking about despite MC's bunk

as they say on the page you refer

"Be warned that both of these terms can be somewhat misleading. The lens focal length does not change just because a lens is used on a different sized sensor — just its angle of view. A 50 mm lens is always a 50 mm lens, regardless of the sensor type."

And just above they state exactly the point I;ve been making

"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."

i.e you alter the magnification to maintain size therefore altering CoC and intern reducing DoF.

as they state

"Note that the above calculator assumes that you have a lens on the new sensor (#2) which can reproduce the same angle of view as on the original sensor (#1). If you instead use the same lens, then the aperture requirements remain the same (but you will have to get closer to your subject)."

Again exactly what I've been saying

So why would you interject in a conversation about the Equivalence between the formast in the discussion with GossCTP stating “that a FF F4 at 200mm is equivalent to a cropped 135 F2.7”

http://www.dpreview.com/forums/post/53084843

And then you state

“But I Don’t see this as equivalent at all.”

Well even the site you provided see that they are equivalent here’s their calc

So if your site you provided see it as equalling then why interject.

I feel as if you have a vague notion on how this work and your attempts at being vague is there to twist your posts to what is true at the end of the day .

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