Help...I need focusing help

[who me?]

Sorry if this is long winded.
I just got a 20D, 17-40L and 100-400L lenses right before Christmas. This is my first DSLR with auto focus lenses. My film stuff was strictly manual focus.
I went on a nice vacation over the holidays and I had a LOT of fun learning about my new camera and how it works. I shot about 450 shots over 10 days. Unfortunately, when I got back to a computer where I could see my pictures, I found many were not focused properly. Some were front focused but many were back focused. Based on the pics, this happened with both lenses.
From what I remember when taking the shots, the focus points illuminated on the subject that I was shooting as well as some illuminating around the subject. I figure 95% of the shots were at ISO 100 and I know a lot of the time the F-stop was open quite a bit so the DOF was usually fairly shallow. I am currently using all the focus points on the camera, the camera focus mode was AI Focus and the lenses were never in manual focus mode.
I know I still have a lot to learn (both with the camera and auto focus in general) and I figure some of this is attributed to the operator and not the camera. I have thought about assigning only focus point but I don't know how limiting that would be.
SO, my question (finally) is, for those of you who have MUCH more experience with the 20D and the EOS system than I, what can you recommend that would help me out with my problem?
I will take any suggestions or info on techniques I can use.

Thanks all for your help,

Mike

[Scottes]

I spend 99.9% of my time using center focus point only.

[S230]

You should try in an controlled environment and set on tripod. Test with both Manual and Auto Focus and see any difference. I recently tried this and realized that my autofocus may be slightly off and therefore not produce very sharp image.

Refer to my loooong link.
http://photography-on-the.net/forum/showthread.php?t=50304

I originally thought that it's a problem with just my camera but it may seem more like quality control. My friend's 20D and my 300D is having these issues.
It can be back or front focus problem as well.

[robertwgross]

Mike, first of all, you know that a narrow depth of field (like you get from a very low f-stop number) can make any autofocus tricky. If nothing else, try simply forcing your camera to shoot with narrower apertures (f/8, f/11, f/16). You probably know that you can goose up your ISO by several stops, from 100 to 400 at least, or to 800 maybe, without getting into too much color noise problem. So, you have one work around right there.

Next, you might find that leaving all focus points illuminated is convenient, but it won't necessarily get you precise autofocus performance. Try selecting just one and freezing on it, then try to see if autofocus performance gets better.

Along the way, you might find that a problem of front-focus or rear-focus is complicated by completely different things like camera shake (especially with the long lens), so you might try shooting that off a tripod just to take camera shake away from the list of possibilities.

Also, and this has been mentioned before a lot. You might try removing any UV filters from the lens front. In a few cases, some funky UV filters have contributed to autofocus problems.

---Bob Gross---

[robertwgross]

I spend 99.9% of my time using center focus point only.

I never get higher than 99.3% using center focus only. I must be missing something. Well, my D60 has only three focus points to begin with.

---Bob Gross---

[digitalfailure]

Was this most apparent with the 17-40 L?

I got that lens 2 weeks ago and it had to be exchanged for another one 4 days latter due to a focus issue, it was very soft and even on manual focus it was still trying to autofocus.

[DLopez]

My solution takes a little practice, but memorizing which button allows me to change the active focus point(s) has been immensely helpful with focusing issues.

I've found many times that in order to track an object (in sporting events for example) and maintain the desired composition, especially when using AI-Servo autofocus mode, the focus point isn't necessarily going to be either in the center of the viewfinder or in the foreground.

Being able to quickly change on-the-fly which rectangle will be the focus point is a good skill to acquire.

It's not that daunting, really. :)

[billsh]

S230, What did you do? Did you send your camera in to have it repaired? I have been noticing my new 20D doesn't produce the sharp images I'm accustomed too. This seem especially true in AI Focus and AI Servo. As a test, I put my Sigma 400 on a monopod and shot it at 1/5000 @ 5.6 at ducks swimming about 40 yards away. The result was they were not sharp. I need to get this resolved, but was told by Canon telephone rep, focusing has not been a problem for 20D's. Any experience you had would be appreciated.

Thanks

[cc10d]

Me too, well almost, at least 90% on that more sensitive center focus. Its tough enough figuring out where one point focuses, let alone all the others. The 20 seems to be much better than the 10 was though. Definately faster and more accurate, especially when using continuous focus, that I use to assist capturing moving subjects, (birds, running animals, cars, etc) that do not have much around them to confuse the camera. I am usually in 1 shot mode. Sometimes I find that I inacurately focus because by the time I press the button, I may have strayed off the desired focus point. Most of my focus issues early in digital, was more my not recognizing that most of the pictures I took with film were veiwed as 3x5 or 5x7 or some 8x10s. Looking at them on my monitor screen I am looking at them as 11x14 or larger. I tend to crop a lot, etc. So I was thinking my lenses were sharper than they really are, and depth of field is much more significant now. I went back a digitized some of those "good shots" and found they were not the quality I was now expecting, or thought they were. All that aside there are cases when the auto focus just is not perfect. But most of problems are not knowing were it really focused. We just did not used to require the level of critical focus or quality of lens, that we now do. We have just upped the anti, and the manufactures are feeding it to us.

Get off the auto focus selection, to the center sensor and try it for a while, I think you will be more satisfied with your results. Just keep shooting, you have some very nice equipment!!

[Mark Kemp]

Also AF works better the more light there is around.
On a bright sunny day my 20D will lock on and focus a racing motorcycle at 5fps and keep all the frames in focus, but last week in a cold dark British winter it missed a squirrel sitting still 3 times out of 4 (on about the same max aperture I think).
AF is excellent but its not infallible sometimes you have to go back to manual

[S230]

S230, What did you do? Did you send your camera in to have it repaired? I have been noticing my new 20D doesn't produce the sharp images I'm accustomed too. This seem especially true in AI Focus and AI Servo. As a test, I put my Sigma 400 on a monopod and shot it at 1/5000 @ 5.6 at ducks swimming about 40 yards away. The result was they were not sharp. I need to get this resolved, but was told by Canon telephone rep, focusing has not been a problem for 20D's. Any experience you had would be appreciated.

Thanks
Wow.. seems interesting that I started another forum and end up here with similar issue. So far, to eliminate guesswork, I went and purchased a 50mm 1.8 lens. This is a prime and shoudl produce much better result. I also got the Sigma 70-300 lens and that indeed produced great photos. Still soft though. as for the 50mm, i am probably still doing something wrong because my images still look soft but sometimes really sharp. I tried using a grey card and it helped a bit but manual focus is good. Probably this weekend, I can finalize what the result is because of more time.
I think something is knocked out of place or Canon's QC is really bad.

The following link is a very long link but it contains sample of images.
http://photography-on-the.net/forum/showthread.php?t=50304

You should try first DOF and then figure out where the focus point is. I think my camera is slightly Front Focused.

Just a note, my friend used a "killer" L lens on his 20D and still dark and not very focused shots.

[S230]

Get off the auto focus selection, to the center sensor and try it for a while, I think you will be more satisfied with your results. Just keep shooting, you have some very nice equipment!!
It's sometimes hard manual focus on fast moving subjects.

[IndyJeff]

Scottes, there is more than one focus point? LOL


One thing to keep in mind as mentioned earlier, the lower your apt number, i.e. 1.8, 2.8, etc, the harder it is going to be to get a good focus. If possible always try and shoot at 5.6 or above.

Until I took my camera away from the race track I didn't even know there was an apt setting below 8.0.....well ok thats a little exagerated but you get the point.

[KennyG]

Scottes, there is more than one focus point? LOL.

I had heard that rumour too Jeff. Someone told me that my cameras had 45 of the pesky things. Can't be true, can it? Only ever seen one square through the viewfinder, ever. :lol: Am I missing something?

[Scottes]

Scottes, there is more than one focus point?
Only 2 more on a D60, I guess. :-)

One of the reasons I got the 20D was the AF point arrangement seemed better than the 10D. The first week with the 20D was when I shot 0.1% of my shots with more than 1 selected. Been there, done that, and once again I use center-point only. ROFL.

[megaweb]

I also experience focusing issue on some of my lenses like 85mm f1.8 , 35mm f2, 17-40mm and sigma 18-125DC

see detail here http://photography-on-the.net/forum/showthread.php?t=53045

maybe you can do some tests like what I did
- D70 Chart Test
- 3 Batteries

[who me?]

All, thank you for your advice and insight. That is why I like this forum. I can always learn from others.
S230, Dlopez - I will be exeprimenting with the focus points in the future. I need to try to characterize what is really happening though. So far, my bet is the user. ;)
Bob - yea, I do realize that I am shooting at close to wide open on many of the shots giving me the super shallow DOF. On many of the shots I can see where a stopped down lens and a deep DOF would help, but to me, this might mask the real issue. The shallow DOF really showed a different point of focus than where my subject is. The best example would be a shot of a Sandpiper on the beach. Although the bird is slightly offset form center, but would be in the circle around the center AF point, the shot clearly shows the focus poing being about 2 feet behind the bird.
Thus more experimentation and learning. This will include bumping up the ISO so I can stop down the lenses and see the effect.
digitalfailure - I noticed some of the shots were with my 17-40 but the majority were with my 100-400. Unfortunately both lenses are showing the issue so I can't blame it on one lens.

Again, thanks for the suggestions and insights.

[cc10d]

S230

Quote:
Originally Posted by cc10d
Get off the auto focus selection, to the center sensor and try it for a while, I think you will be more satisfied with your results. Just keep shooting, you have some very nice equipment!!


It's sometimes hard manual focus on fast moving subjects.
__________________
S230

I agree with you fully, I was not clear, I meant off of auto selection of the focus point. I would not get very many shots focused if it were not for the autofocus lenses and cameras. I intended to recomend using the central auto-focus point. It has both horizontal and vertical components and if on the 20D, A more accurate focus, especially with f2.8 or faster lenses. I like the 'joystick' button to select focus point when appropriate. chuck

[planesh00ter]

I have had similar problems ,posted b4, with my 100-400. Even in airplane shots against a blue sky, the planes are out of focus. Shot a bunch of nite shots last night with my 28-70 and didn't have the stop down DOF luxury. About 50% were in focus. ( the 20d metering was awsome) Some I think the camera picked up a focus point from the ground in the foreground. Forgot to ctr focus, as I was in a hurry to get shots I didnt expect.
I do a lot of shots about 30deg off the side , or 10-11oclock from plane perpective, ( aircraft portraits) with the plane full frame and started ctr focusing at the ctr of planes body then framing the pic, like the manual describes, and getting more reliable focusing, and dof.
In the past year I have gotten very serious and shooting hundreds of frames a day. The depth of my knowledge is amazing, that is the knowledge of what I do not know, and the ever increasing overwhelming awe of professional photographers. I am waiting to turn the corner and make positive steps toward true understanding of this art. Ma hats off to ya all.