Auto focus dilemma - DPChallenge Forums

Canon EF 70-300mm f/4.5-5.6 DO IS USM

02/06/2006 01:52:04 PM · #1

I was out shooting the other day. Over 200 shots and the focus was off-subject on all of them. It seems autofocus was focused on something other than what I was shooting. What gives with this?

cpanaioti

Canon EOS-40D

02/06/2006 01:54:25 PM · #2

Which focus point do you have set?

Did the camera re-focus when you recomposed shots? Did you wait for the focus light in the viewfinder to stop flashing before recomposing?

FranziskaLang

Nikon D100

Tamron SP AF 28-75mm f/2.8 XR Di for Nikon

02/06/2006 01:59:08 PM · #3

Nikon lets you choose a different focus point, I'm sure Canon does that, too. I sometimes set mine to other than the middle without immediately noticing. Have you checked your settings?

glad2badad

DJI Mavic Air 2

Sears 55mm f/1.4 M42

02/06/2006 02:01:15 PM · #4

Originally posted by dsmeth:

I was out shooting the other day. Over 200 shots and the focus was off-subject on all of them. It seems autofocus was focused on something other than what I was shooting. What gives with this?

Sometimes it pays to "chimp"! ;^)

vadvirag

Canon EOS-350D Rebel XT

Canon EF 50mm f/1.8 II

02/06/2006 02:05:49 PM · #5

Originally posted by dsmeth:

I was out shooting the other day. Over 200 shots and the focus was off-subject on all of them. It seems autofocus was focused on something other than what I was shooting. What gives with this?

I have the same problem with my camera, though it's not an SLR. It was better before, but nowadays seems like it totally forgot focusing. I always wait until it stops noising, and I only shoot after. Manual focus is terrible on this cam as it's just a cheap compact camera with quite a bad screen...

Canon EF-S 18-55mm f/3.5-5.6 USM

02/06/2006 02:06:59 PM · #6

Originally posted by glad2badad:

Originally posted by dsmeth:
I was out shooting the other day. Over 200 shots and the focus was off-subject on all of them. It seems autofocus was focused on something other than what I was shooting. What gives with this?

Sometimes it pays to "chimp"! ;^)

It was set on AI Servo and Evaluative. As far as chimping goes, what's the point? You can't tell anything from those stupid little LCD displays anyhow. Lotsa times I've looked at the display and thought they looked fine only to download later and find out the shots are crap.

rox_rox

Canon EOS-20D

02/06/2006 02:18:48 PM · #7

Doesn't your camera let you zoom in on the LCD? I took a bunch of shots once and realized (halfway back to the car) that my dioptric adjuster was set wrong. Zoomed in and saw they were OOF. Glad I did, or I would have missed the chance to reshoot.

I have focus issues with mine too. I'm thinking it's my cheap lense, though, and have just taken to using MF most of the time.

Message edited by author 2006-02-06 14:20:50.

Mr_Pants

SiPix Blink

02/06/2006 02:35:18 PM · #8

Originally posted by dsmeth:

Originally posted by glad2badad:

Originally posted by dsmeth:
I was out shooting the other day. Over 200 shots and the focus was off-subject on all of them. It seems autofocus was focused on something other than what I was shooting. What gives with this?

Sometimes it pays to "chimp"! ;^)

It was set on AI Servo and Evaluative. As far as chimping goes, what's the point? You can't tell anything from those stupid little LCD displays anyhow. Lotsa times I've looked at the display and thought they looked fine only to download later and find out the shots are crap.

AI Servo might be a way of explaining your problems. If the focus point was slightly off the intended subject (particularly if everything is moving about rapidly), the camera might refocus onto the background and, with no focus confirmation 'beep' you might not know. Just a thought.

What lens were you using? There were a million and one threads on DPReview regarding back-focus issues with the 70-200 f4, particularly with the 300D. I've not experienced the problem myself, but I did have to make a refund to an Ebay purchaser who bought my 70-200 to use with a D60 and couldn't get a single shot out of it in focus.

Canon EF 17-40mm f/4L USM

02/06/2006 02:44:19 PM · #9

I was using my 70-200 F/2.8. I find focusing issues mostly when I tend to have dark subjects in darkened areas. Like birds in trees. Auto focus will focus on a twig in the tree and not on the bird. I have some nice clear shots of twigs and branches with fuzzy birds.

I was using AI Servo because I was shooting flying eagles.

Message edited by author 2006-02-06 14:45:32.

LoudDog

Canon EOS-350D Rebel XT

02/06/2006 02:50:24 PM · #10

I wouldn't use evaluative. Put it on one of the spots so you can chose what to focus on (i.e. the bird and not the twig).
With evaluative the camera picks what to focus on for you, and it won't always be right (i.e. the twig). This sounds like what happened to you.
If you are shooting a high aperture this won't be a big problem, but if you are shooting low aperture (shallow DOF) it will.

Message edited by author 2006-02-06 14:52:12.

glad2badad

DJI Mavic Air 2

Sears 55mm f/1.4 M42

02/06/2006 02:58:03 PM · #11

Originally posted by dsmeth:

Originally posted by glad2badad:
Sometimes it pays to "chimp"! ;^)

As far as chimping goes, what's the point? You can't tell anything from those stupid little LCD displays anyhow. Lotsa times I've looked at the display and thought they looked fine only to download later and find out the shots are crap.

My bad. I'll keep the helpful sarcasm to myself. The zoom feature on my LCD works pretty well...been helpful a few times when uncertain.

Good luck figuring this out. ;^)

Strikeslip

Canon EOS-5D

Canon EF 100-400mm f/4.5-5.6L IS

02/06/2006 03:01:39 PM · #12

Sometimes it would be cool to have a "focus bracketing" setting, sort of like the exposure bracketing.

When I want to focus in low light, I've been switching to manual, but that's not easy for me as my eyesight isn't the greatest.

snapz

Canon EOS-20D

Quantaray AF 70-300mm f/4.0-5.6 High-Speed for Canon EOS

02/06/2006 03:39:42 PM · #13

Originally posted by glad2badad:

Sometimes it pays to "chimp"! ;^)

Soooo someone want to explain what "Chimpimg" means for this n00b?

PhilipDyer

Canon EOS-5D Mark II

Canon EF 24-105mm f/4.0L IS

02/06/2006 03:54:17 PM · #14

"Chimping" just means looking at your or someone else's pictures in the viewfinder and going, "ooh ooh!" You're sorry you asked now, aren't you? ;-)

I found that any time I let the camera choose what to focus on, it virtually assured poor focusing. I set focusing to center point only and just focus on my intended subject and then recompose the shot.

And you can zoom in to check focus on the LCD, which I've done several times when it loooked like the photo might be a bit soft. If you have any doubt about your focus, take another shot.

glad2badad

DJI Mavic Air 2

Sears 55mm f/1.4 M42

02/06/2006 04:06:11 PM · #15

Originally posted by PhilipDyer:

... I set focusing to center point only and just focus on my intended subject and then recompose the shot. ...

I'll focus and recompose also, but one thing I've found to be careful of (especially with a narrow DOF) is that when moving to recompose that you don't take the intended subject slightly out of range. I'm finding myself using the focus area selection mode more frequently. Then I can choose one of nine focal points and usually not have to recompose.

Bear_Music

Samsung Galaxy S21, S21+, S21 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

02/06/2006 04:10:41 PM · #16

This is why we have tripods and eyes; so we can use manual focus and get it right :-) I'd say I use MF well over half the time, myself.

Robt.

Mr_Pants

SiPix Blink

02/06/2006 04:15:57 PM · #17

If you have trouble focussing on dark subjects against light backgrounds, it may be that the subject is so dark that it lacks enough contrast for the AF system to find something to lock on to. The focus points, I believe, actually extend beyond the markers on the AF screen, so may well lock onto the branches, as there is enough contrast there (dark branch against bright sky). If the subject is, indeed, quite dark, perhaps try aiming at the edge of the subject where there is, clearly, contrast between it and the background. Obviously, this may well be a little to difficult for anyone to achieve if the subject is a fast-moving bird.

kirbic

Canon EOS R5

Canon RF 24-70 f2.8 L IS

02/06/2006 06:45:31 PM · #18

As I think has been hinted at here, evaluative is, in these cases, gonna screw you up royally. Those twigs have really high contrast edges that the AF system loves to find You have to direct the attention of the system where YOU want it, by choosing a specific focus point.
Normally it's best to choose the center focus point. I don't know for sure about the XT, but on most Canons the center point is a cross-type sensor, which gives better focus accuracy. It also gives the most options for later cropping, which will nearly always be necessary with such shots anyway.
If you're having trouble judging whether the focus is on the correct "subject" in the viewfinder, make sure the diopter adjustment is set correctly. You should be able to tell when there's significant misfocus.
You're doing the right thing using AI Servo for in-flight shots. Aim the selected focus point at the edge of the subject, not the center, in backlit situations, to take advantage of the high-contrast edge.

Message edited by author 2006-02-06 18:45:51.

sir_bazz

Pentax K-5

Pentax FA 50mm f/1.4 AF

02/06/2006 07:51:53 PM · #19

Sounds like a good excuse to upgrade your camera. :)

One with a brighter viewfinder for useable manual focus and a larger/higher res LCD for decent shot reviewing.

bazz.