[Widowmaker]

This may not be the right place but I wanted to post here since its dealing with a digital slr and macro lens. I just got a Sigma 105mm EX Macro lens and it seems like I cannot get my entire subject in focus. I know that this will be characteristic to a certain extent depending on how deep the subject extends into the background but for example this fly image, the feet and the wing tip are not in focus. Is this characteristic of macro lenses?

[eric s]

I don't know for what settings you were using on this picture, so I can't say for sure. But the depth of field in macro work can be extremely small. Amazingly small. From what I understand, f22 is not an uncommon setting to try to increase the DOF as much as possible.

What you show here is smaller than I would expect, but I am no macro expert by any means. You might want to post the question in a forum which regularly shows macro work (since there doesn't seem to be a dedicated macro forum.) Someone who does macro work might be able to give you more info.

Eric

[Widowmaker]

Originally Posted by eric s

I don't know for what settings you were using on this picture, so I can't say for sure. But the depth of field in macro work can be extremely small. Amazingly small. From what I understand, f22 is not an uncommon setting to try to increase the DOF as much as possible.

What you show here is smaller than I would expect, but I am no macro expert by any means. You might want to post the question in a forum which regularly shows macro work (since there doesn't seem to be a dedicated macro forum.) Someone who does macro work might be able to give you more info.

Eric

Thanks for the response Eric. I will try to find somewhere to post this. I was using f5 - 1/400 on this shot. I guess I could have stood to make some adjustments.

[p645n]

You'll have to stop down your lens my friend!

Depth Of Field (DOF) narrows as you get closer to an object. (This getting close is labeled -- or mislabeled; depends on your opinion -- macro).

Somewhere on the top deck of your DSLR is an o with a - through it. This is the film plane (or sensor plane for digital) -- the ground zero of your camera if you will. Distances are measured from there, not from the front of your lens.

Now, take your fly. Lets say it's one foot away from the film plane and your lens is at f5. At that f-stop the DOF you have is less then 1/16 of an inch (about 1.6mm). Obviously our friend the fly (who may be 1/4 inch top to bottom) is not going to be completely in focus.

But...say we shoot the exact same shot with the exact same camera/lens at f22. Suddenly we'd have .28 of an inch (about 7mm) -- and that is slightly more then the 1/4 inch of depth we need if we want to see our friend sharp -- from the tip of his adorable head to his funky little feet.

And to close;

DOF changes whenever we change the focal length of our lens or our f-stop.

If you want a copy of a rather slick DOF calculator you can use Mikes that is found here; http://tinyurl.com/shvd
(sorry don't know if this will turn into a live link...I've only made one other post)

And please…feel free to ask for clarification if I've bumbled something up...jim

[Widowmaker]

Originally Posted by p645n

And please…feel free to ask for clarification if I've bumbled something up...jim

You explained it very well as far as I'm concerned and I was wondering what that little o with the line through it was :)

I was use to taking photos with the 18-55mm lens and was expecting for things to be the same with this when apparently they are not. F8 with the 18-55mm lens was usually sufficient.

Thanks for this valuable information.