20D back focus on wide angle!

[ant]

20D back focus when using wide angle.

When using 17-40L, at the 17mm, center focusing, notice the back focus is BAD!

Thoughs is my len problem, try out on 10D & 1D, focus is perfect.

Call 2 of my friend who own 3 set of 20D, they tested with 16-35L, 17-40L and 20-35L, at the wide angle side...all have same problem!!!

Can someone test out whether all 20D have this problem?
Method to Test: Use center point focus, focus on the face or eye...shoot somebody from a distance at the wide angle side(between the range of 16mm - 20mm).

PS: Notice it happen only when using wide angle.

If no choice and need to shoot at wide angle, we, my friend and i, zoom-in close, focus on the subject than lock the shutter button(hold it half way) and zoom out and press the shutter button. Image turn out sharp.

[kiwi2]

Hi ant,

I'd suggest you have your 20D and lens checked by Canon. I did not encounter the problem you described.

[ant]

Originally Posted by kiwi2 Hi ant, I'd suggest you have your 20D and lens checked by Canon. I did not encounter the problem you described.

Hi kiwi, thank for reply.

I tested and my friend tested too....total 4 set of 20D all have same problem.

Definally am sure it not the lens problem as we had been using in 10D, 1D and without any problem.

It just funny the back focus happen when on wide angle....

My friend had sent down 2 set of 20D to Canon service center, it seem don't have a good solution. The only thing they answer is Canon Len is calibrate to be use in film camera but when in use in digital...it happen back focus issue.

To what i know, when 10D is out, it had the same issue. If 10D back focus issue can be solve, I think there should be able to solve the same problem.

I been waiting so long for the 20D to be out in the market.... finally it arrived. But....having problems... Had spent so much to buy L len and yet....back focus on my new 20D....disappointed.

[ahbeng]

was the subject in center when you used the center focusing point? did you try to use the other focusing point instead of (focus, lock recompose method)? if possible, could you post a picture?

[kiwi2]

Hi ant,

That's strange... Maybe it's the batch of 20D's that you and your friends got? Maybe that's why some people are afraid to buy a new DSLR model so soon because of all these issues.

Personally, I've not encountered back focusing b4 though I've read so much about it. The worst one I heard was the back foucusing of 24-70mm L on the 10D that some experienced.

All these problems do sound very ridiculous considering you pay literally thousands of dollars and get peanuts.

Somehow, it makes one feel the robustness in digital technology is not 100% there yet like films. I mean, all these lock up issues, back focusing.... It's like they are still in the R&D stage and the engineers are groping around on certain issues. I'm sure give another 5-10 years, technology will improve in leaps and bounds and all these will be ironed out.

But as long as the equipment works for me, I won't worry about them.

Hope you can find a way out of your situation.

[Tzuen]

It is just a matter of getting the lens calibrated by Canon for your 20D, bring both down to Canon and get it done.

[ant]

Originally Posted by ahbeng was the subject in center when you used the center focusing point? did you try to use the other focusing point instead of (focus, lock recompose method)? if possible, could you post a picture?

I use the center focus, lock recompose method.

Most bad pics had deleted, below a test using :-
Camera Mood = Manual
Focus Point: Center (lock & recompose)
Shitter Speed = 1/100 sec
F-Stop = f4
ISO = 200
Focal length = 17 mm
Flash = 550 Ex Fired

...Sample below isn't the worst one.

1) The circule in red is where I focus:-

=== Image removed ===


2)100% crop:-

=== Image removed ===


As for the sample, the face should be sharp but it's out of focus. Instead the back ground, it seem to be sharp.

I didn't use other focus points as had been use to the Center focus method.

[ant]

Originally Posted by Tzuen It is just a matter of getting the lens calibrated by Canon for your 20D, bring both down to Canon and get it done.

Hi Kiwi & Tzuen, thx for reply.

If I bring the lens to calibrate for the 20D, than when I use it in other camera, the focus will be out.

I had been using it on 10D and it focus perfectly.

[kiwi2]

Originally Posted by ant Hi Kiwi & Tzuen, thx for reply. If I bring the lens to calibrate for the 20D, than when I use it in other camera, the focus will be out. I had been using it on 10D and it focus perfectly.

Hi Ant,

Hmm, even without the crop, can already tell it's not in focus.

Yah! I couldn't believe it when I was told this. It's just crazy. I'm not a techie nut but could someone kindly explain why this kind of thing should happen? A lens is a lens right and by common expectation, shouldn't it focus exactly the same no matter what the body is?

[ant]

Originally Posted by kiwi2 Hi Ant, Hmm, even without the crop, can already tell it's not in focus. Yah! I couldn't believe it when I was told this. It's just crazy. I'm not a techie nut but could someone kindly explain why this kind of thing should happen? A lens is a lens right and by common expectation, shouldn't it focus exactly the same no matter what the body is?

Hi Kiwi,

I actually had the camera for few weeks and I didn't notice till my friend borrow my whole set of equirements for a wedding shoot. He show me some pics and some are not useable at all(worst than the sample)! I had taken some pics 2 weeks ago and I notice some are out of focus and i still think is my own fault(focus too fast and capture).

Maybe you should really test out urs using wide angle(16 or 17 or 20...etc) and enlarge to see whether you have the same problem or not.

Just imagine if someone didn't notice (just like me till my friend show me his pics) and capture some important Events, how he/she able to answer to client?

Lucky my friend shoot alots using the backup camera with my 50mm & 85mm prime.

[zod]

Originally Posted by ant I use the center focus, lock recompose method.

this is the reason why your focus is out
http://visual-vacations.com/Photogra...pose_sucks.htm

[Tzuen]

Zod beat me to it. Especially noticable when doing portraits up close. You should try another test with the camera mounted on a tripod using the center focus point without recomposing. In fact use the self-timer.

That being said, the photo you showed does have the point of focus in the center, so why did you recompose?

[oeyvind]

ant: quick, quick... sell us your defective 20D cheap...

[r52lanc]

Looks to me like the subject moved. Shutter speed is 1/100sec only. Assuming you were ~5ft away from the subject, DOF would be 4.7ft. That means everything should be in focus.

Depth of field calculator is here.

Quote: use the center focus, lock recompose method. Most bad pics had deleted, below a test using :- Camera Mood = Manual Focus Point: Center (lock & recompose) Shitter Speed = 1/100 sec F-Stop = f4 ISO = 200 Focal length = 17 mm Flash = 550 Ex Fired ...Sample below isn't the worst one.

[yf_chua]

i came across this website, maybe it is useful to all of you.

http://www.photo.net/learn/focustest/

Hope you all can post the image for all of us to see after testing.

it is interesting...

[henavs]

I agreed with the focus-recompose article showed by Zod, especially if u use shallow DOF...

Tat's what the multiple AF points are for...

Now tat 20D have the option "Multi-controller Direct" (basically one-touch AF select). Just flick the joystick to the AF point u wan & fire away. It is a very good feature, make use of that...

[ant]

Hi Guys,

First I really appricate the thoughs and helpful links from Kiwi, zod & yf_chua. Here would like to say thxssss.

as for Tzuen:-
You should try another test with the camera mounted on a tripod using the center focus point without recomposing. In fact use the self-timer.


I had try some many time, the sample which i post is not the worst! (As I mention, I had deleted those pics I took past weeks and when u ask for sample, I just re-take again to post it). Also it not just happen to me only as i had mention 2 of my friend have the same problems. There had been a PRO for so many years, you mean they don't know how to use a camera? 35mm camera is just a toy for them!

That being said, the photo you showed does have the point of focus in the center, so why did you recompose?
It just a sample to show, I had crop and resize or else file size is not too heavy for viewing on net.

For oeyvind:-
ant: quick, quick... sell us your defective 20D cheap...
I post for helpful advices, feedback the problems of a new camera. Whoever here intend to purchase the same camera, they're able to check before purchase.

So if you feel joys with the problems I face, instead of giving a advice. Thank you and I rather hope you dun reply the thread. (Hopefully you will never face any unlucky purchase)...

For r52lanc:-
Looks to me like the subject moved. Shutter speed is 1/100sec only. Assuming you were ~5ft away from the subject, DOF would be 4.7ft. That means everything should be in focus.

You mean the subject move so fast as using 1/100 are unable to capture? HE is just standing there using a computer, noone will dance or jump when using a computer. His speed is not as fast as a car.

Yes DOF should be in focus but now you see it....it out of focus.

----

Abit disppointed sharing the info and problems I had here. I should rather keep it to myself or turn to Canon Support. I though someone can offer help and advice(some of them did, thx), but instead I got some unhelpful and fingers pointing at me.

[Zplus]

Hi ant,
DSLR is a little different from film 35mm. Unless you look at prints with the loupe, you are unlikely to see the subtle differences. Also don't forget the 20D is effectively only taking the center crop of your 35mm film plane. So you are gonna notice a lot more imperfections in the lens with a DSLR.

The article on the "lock and recompose" is correct. Esp for wide angles. You will get OOF esp if the subject is near and dof is shallow. Think most the the poeple here are humorous and like to post in a toungue-in-cheek manner so do not take it to heart.

Try using the nine AF points instead of the lock focus recompose method. Make you are in one shot AF if your subject is not moving. Also try to place the AF points on a high contrasty area of the person's face (eg eyes). If your camera and lens still insists on getting focus on the background instead of your iintended target then you may really have a focus problem. Your should send both the camera and lens to canon for calibration. I have dealt with canon supprt before and they are always helpful. They have never given me that the lens is only used for film camera nonsense... if so, I would have gotten his name and if he was not joking... I am sure his boss would not be amused.

My own 20D works very well with all my lenses. It focuses slightly behind the target with my EF 85mm f1.8 @ f1.8. Still its usuable at f1.8 coz the dof still covers my target area. Other than that, its been happily getting me dead on accurate focusing.

[aaron001]

it goes to show the confidence ppl have with canon

[knoxknocks]

Hey ant,

Can understand your frustration with the problem but I guess the people who posted are trying to help by giving suggestions, but maybe you're just too frustrated to "listen". In any kind of a discussion forum, there will be people who may post comments that don't contribute to solving your problem. That's just the way of life. That's why you have the right to ignore mah...

Anyway, this forum is just another avenue to ask for help, and not the only channel rite? As you mentioned, if can't solve problem can always turn to Canon.

FWIW (and not at the expense of making you feel worse), I use a WA 12-24mm from Sigma on a 20D (albeit not Canon) and don't experience the back focus problem that you have (yet )