DOF and Cropping take 2

Started 10 months ago | Discussions thread
ForumParentFirstPreviousNextNext unread
Flat view
Ian Stuart Forsyth
Senior MemberPosts: 1,892Gear list
Like?
DOF and Cropping take 2
10 months ago

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

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 ?

I haven’t read over the whole page so I will trust you when you say with everything you have provided here as true. But what if I can prove that they are wrong (if I rely on what you have said above that cropping has no effect on DOF)

What if I crop my k5 shot with 300mmF2.8 by a factor of 1.8

K5 shot with the 300mm F2.8 Cropped by 1.8 will have a resulting image that would share the same DOF and FOV as a k5 shot with a 540mm lens at F5

Below is a screen grab using the DOF calculator of a trusted site that I used more than once & that I believe to be true

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?

-- hide signature --

The Camera is only a tool, photography is deciding how to use it.
The hardest part about capturing wildlife is not the photographing portion; it’s getting them to sign a model release

 Ian Stuart Forsyth's gear list:Ian Stuart Forsyth's gear list
Pentax *ist DS Pentax K10D Pentax K20D Pentax K-7 Pentax K-5 +19 more
Nikon D7100 Nikon D800 Pentax K-5
If you believe there are incorrect tags, please send us this post using our feedback form.
ForumParentFirstPreviousNextNext unread
Flat view
Post (hide subjects)Posted by
ForumParentFirstPreviousNextNext unread
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow