Fixed focal-length focussing

[vidar42]

I decided to try the challenge of putting my 50mm fixed focal-length lens on my Nikon and work with that for a while. It's a manual focus lens which is another added challenge of course. It's an f2.8 lens (yay for fast lens).

My issue is that even when it looks like I'm in perfect focus, when I zoom in after the photo is taken, it's either slightly blurry or just really blurry. I rarely get an in-focus shot. I've switched to AP mode and set it to f2.8 as I want a good shallow DOF. However when I changed it to F22, I seemed to get a cleaner focused photo.

What I'm wondering is...does that make sense? Does my fast lens (compared to my kit lens anyway) cause my focus issue? Or is it just me? I didn't touch my focus ring but changed my aperture and got a cleaner photo.

I've heard of "sweet spots" on a lens as well, is this perhaps what I am encountering?

Any advice at this point is greatly appreciated.

[Liz Caldwell]

Your manual focusing might just be off by a hair... As you stated, 2.8 is a very shallow DOF, so a little off would make a huge difference; whereas with the 22 it wouldn't be nearly as noticeable... If you could post a sample of the shallow one I can take a look and let you know if I see anything

[Rentham]

Originally Posted by vidar42

What I'm wondering is...does that make sense? Does my fast lens (compared to my kit lens anyway) cause my focus issue? Or is it just me?

Yes, it makes sense. It is highly likely that your results are user error. Manual focus can be tough, especially when you are working with very little depth of field. When you stop down to f/22 you have far more depth of field so the chances that your subject is acceptably sharp increases.

However on that end of the aperture spectrum you start to deal with diffraction. Unless there is a hardware issue your 50mm can produce good results wide open. You probably just need more practice focusing.

[vidar42]

Originally Posted by Rentham

. You probably just need more practice focusing.

That is a distinct possibility too. I'm too used to AF. I will practice over the next few weeks trying to focus on objects with a shallow DOF and see what I can do. I find the shots are more striking that way...Personal preference I guess...