DPChallenge: A Digital Photography Contest You are not logged in. (log in or register
 

DPChallenge Forums >> Photography Discussion >> Autofocus or Manual Focus?
Pages:  
Showing posts 1 - 6 of 6, (reverse)
AuthorThread
06/02/2009 01:12:18 AM · #1
So, which do you use?
For anyone who uses Manual focus, do you use focus screens, or viewfinder magnifiers?

I'm interested because I have a Canon 400D, with a Sigma 70-200 2.8 lens that frustrates me no end. I've had some beautiful shots from this lens, but on bad days, this lens accurately focuses about 1 shot in 10. I've been through all the technical issues. It's not consistent front or back focus - it's just variable, and certainly worse on some days than others. It's not the camera - the same lens does the same thing on my friend's 350D. It's not the lens, because it happens on other lenses on the same body. On a full-body shot, it might front/back focus by up to a metre, worst case. On a head-shot, plus or minus 20cm is common. Tried a 50mm 1.4 lens in the shop today, and it does the same thing. Also tried it on a 50D, and it was better, but the focus definitely still moved around from shot to shot, in front and behind the poster I was focused on. The guy in the shop said that it's pretty much par for the course with autofocus on wide aperture lenses, particularly on the bottom end SLRs. He told me that he uses manual focus, and it's pretty much the only way to get thin-dof shots in focus. He recommended a viewfinder magnifier, to help me see when the shot is focused, because I've tried, and my efforts at manual focus through the viewfinder are worse than the autofocus, even on a completely stationary focus chart, with a tripod.

So, who else is frustrated with poor performing autofocus on wide aperture lenses, and have you managed to get better results with manual focus?
06/02/2009 02:11:10 AM · #2
I had exactly the same problem with my Sigma 70-200, with my D300. I was so frustrated that I sent it back to the shop to have it checked out, but they said it was ok. It sat on the shelf for a while, but then I had to use it for something again, and I discovered that the main problem is that the lens is highly sensitive, it has no VR, and needs a speed of AT LEAST 1/120 sec in order to focus accurately. Now that I've worked that out its working fine, I haven't had a problem - it might be worth looking at, as like you, I was positive it was a focusing issue but it was a speed issue.
06/02/2009 02:19:40 AM · #3
Thanks for the suggestion. Yes, I'm aware of this, and low shutter speeds can certainly ruin a shot. At 200mm you have to go at least 1/300s, but that's not the issue here. This problem still happens sitting on a sturdy tripod, and shooting at 1/1000 and faster. I was shooting in the store today on the 50mm at 1/400s.

Looking at some shots, it is often easy to see that something else in front or behind the focus point is in perfect focus.
06/02/2009 08:01:13 AM · #4
Are you using multi-point autofocus? I found that it generally picks any point but the one you actually want in focus.
06/02/2009 09:09:56 AM · #5
Yep, been there too. :) I am almost always using centre point only focus. I sometimes think it is improved a little if I use all focus points, I guess because it has the chance to find several more focus points to measure off, and average out the errors. But as it's not reliable, it's hard to say for sure if it's better or worse in any specific test.

So, anyone else using manual focus because auto isn't good enough?
Has anyone tried a viewfinder magnifier?

Message edited by author 2009-06-02 09:12:28.
06/02/2009 09:23:14 AM · #6
Originally posted by surfdabbler:

Yep, been there too. :) I am almost always using centre point only focus. I sometimes think it is improved a little if I use all focus points, I guess because it has the chance to find several more focus points to measure off, and average out the errors. But as it's not reliable, it's hard to say for sure if it's better or worse in any specific test.

So, anyone else using manual focus because auto isn't good enough?
Has anyone tried a viewfinder magnifier?


i tend to use manual focus in lowlight situations if i can afford the time to do so (i.e. non moving subjects). especially with the more finicky lenses (i'm looking at you, 50mm f/1.8)
Pages:  
Current Server Time: 12/05/2019 01:06:30 PM

Please log in or register to post to the forums.


Home - Challenges - Community - League - Photos - Cameras - Lenses - Learn - Prints! - Help - Terms of Use - Privacy - Top ^
DPChallenge, and website content and design, Copyright © 2001-2019 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Proudly hosted by Sargasso Networks. Current Server Time: 12/05/2019 01:06:30 PM EST.