20D back focus on wide angle!

[ant]

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.

Hi Zplus,

Appricate you reply, thx

BTW I have drop by Canon Service Center this morning, too bad these 2 days their department are too busy with few L-lens servicing.

But they are very helpful and they ask me to drop by Friday morning with my camera & len for calibration. It will take few hours.

Just feel funny the problem happen only when using wide angle(me & my freinds, especially on 17-40L & 16-35L). I had also try the 50mm, 85mm & 28-70L it seem focus perfectly.

Happy to hear you have got a great camera. I really like the 20D alots except just wanna to solve the back focus issue on wide angle.

 

[knoxknocks]

Oh yah, I usually test my lenses for back/front focusing problems using this test chart:

http://md.co.za/d70/chart.html

Although it was written by a D70 user (well written!), you can always use it to test at different FLs...

My 2cents.

 

[goering]

Can you retest your problem on a stationary object (to eliminate the possiblity of subject movement) with high contrast to see if this problem is repeatable? Tripod mounted is preferred although wide angles normally don't require that

You mentioned that the problem is especially noticeable at 16-17mm. How about 24mm?

 

[Zplus]

Appricate you reply, thx
~snip~
Just feel funny the problem happen only when using wide angle(me & my freinds, especially on 17-40L & 16-35L). I had also try the 50mm, 85mm & 28-70L it seem focus perfectly.

No problem man!

I am sure they will calibrate it nicely for you. I have a friend here who sent in the 70-200 f4L too for back focus. Also I have heard some focusing issues with 16-35L over in dpreview. But so far, the 17-40Ls are usually ok. Maybe its just the lens.

 

[ant]

Can you retest your problem on a stationary object (to eliminate the possiblity of subject movement) with high contrast to see if this problem is repeatable? Tripod mounted is preferred although wide angles normally don't require that

You mentioned that the problem is especially noticeable at 16-17mm. How about 24mm?

Yes, tested over and over with stationary object, confirm back focus issue on wide angle.

Even test using other focus points, back focus confirm.

My friend tested with his 24-70L, at 24mm, focus perfect.
I tested with 28-70L, at 28mm, focus perfect.

 

[Tzuen]

Sorry if I didn't seem helpful. I was trying to be constructive. Anyway I took my 17-40mm f4L which I have not used with my 20D before and tested it. These were taken on a self-timer indoors. All shots were taken at 400 ISO at f4. The VHS tapes (remember those?) are arrange in a staggered pattern with about 1cm difference. They are staggered forward from left to right. The white circle added in PS shows the focus point. Here are the results:

Canon 17-40mm f4L - f4- 17mm - Full frame

Canon 17-40mm f4L - f4- 17mm - 100% Crop

Canon 17-40mm f4L - f4- 40mm - Full frame

Canon 17-40mm f4L - f4- 40mm - 100% Crop

Looks good to me. No sharpening done, just resized for the web and converted to sRGB.

 

[jeff49er]

Yes, tested over and over with stationary object, confirm back focus issue on wide angle.

Even test using other focus points, back focus confirm.

My friend tested with his 24-70L, at 24mm, focus perfect.
I tested with 28-70L, at 28mm, focus perfect.

I understand what u go thru. Hope your situation improves

I have been using the 20D with my 24-70L more than a month and I have not experienced back foucussing.

 

[ant]

Sorry if I didn't seem helpful. I was trying to be constructive. Anyway I took my 17-40mm f4L which I have not used with my 20D before and tested it. These were taken on a self-timer indoors. All shots were taken at 400 ISO at f4. The VHS tapes (remember those?) are arrange in a staggered pattern with about 1cm difference. They are staggered forward from left to right. The white circle added in PS shows the focus point.

Thx Tzuen

You have a great 17-40L & 20D. It look very sharp.

Thank for taking your time to test out. At least now I know it not all 20D had this problem. Just it happen all together to me & my friend who own it.

Enjoy your new lover(20D) and "kiss her more"(shoot)

 

[freelancer]

I use the center focus, lock recompose method.

There is a Canon document on lock and recompose (FLR) which basically says that you got to watch out particularly for shallow DOF.

And no, the 17-40 focus fine with the 20D.

 

[CaeSiuM]

It's always easy to blame the equipment rather than to admit that one doesn't understand the equipment well enough.

 

[oeyvind]

It's always easy to blame the equipment rather than to admit that one doesn't understand the equipment well enough.

:thumbsup: :thumbsup: :thumbsup:

 

[ant]

It's always easy to blame the equipment rather than to admit that one doesn't understand the equipment well enough.

Good one!

I will tell my friends this...(own the back focus camera)who had been many years of a PRO since in London and Singapore. And will ask him how dare he could bill client at a rate of $3000+ for actual day wedding photography.
---

It's also always much more easy to keep silent rather than giving remarks and not providing a helping hand.

 

[CaeSiuM]

Good luck then.

 

[kelster]

hmm..donno if this is old news...but here's some Auto Focus accuracy test that Phil had done for the 20D in his updated review...no big problems leh...

http://www.dpreview.com/reviews/canoneos20d/page16.asp

 

[bkling1]

Other long range focus problem for Canon 20D as reported in Malaysia forum..

http://www.photomalaysia.com/forum/index.php?showtopic=1216

 

[eudoofus]

Other long range focus problem for Canon 20D as reported in Malaysia forum..

http://www.photomalaysia.com/forum/index.php?showtopic=1216

flawed examples...

low contrast, how to focus properly?

too complicated details around the centre AF point, how can he expect the AF to pick out the bird? he should go closer or get a longer lens, instead of complaining that the camera can't do pinpoint focusing. the box is only an indication, and not the exact square where the AF would work.

in fact all the 9 points have different focussing characteristics, some work with horizontal details, some with vertical details, some with both vertical and horizontal details, and some have higher sensitivity when a fast lens is used. you just have to understand the limitations of the system, instead of sulking that the system is not perfect and idiot proof.

 

[freelancer]

Other long range focus problem for Canon 20D as reported in Malaysia forum..

http://www.photomalaysia.com/forum/index.php?showtopic=1216

I have responded to the same post linked above. While there is always a possibility of cameras that have focus issues, it is not clear from the pics posted whether it is technique or the photographer being new to handling the camera.

It does not also help when a Nikon D70 owner (with good intentions) tries to offer experienced advice without having some feel of how the Canon AF system (and 20D) would operate. I would take some of the comments posted with some grain of salt

 

[ant]

After posting the back focusing issue few weeks ago, I am back with a answer.

Me & friend bring to Canon Service Centre. Was told alots user feedback same problems.

After taking hours to check through and they even get back to Canon HQ. The Answer is... all 20D have same problem. Just that some user still yet to notice it.

It only happen with wide angle len due to the 20D had increased the size of the sensor (larger than 10D inorder to achieve FAST focusing). That's why when in wide angle, the subject which you focus it become smaller and the focus point cover a larger area, it will pick any area within the focusing point which has more contrast.

So when it pick the area behind the subject(still within the focusing point which are more contrast) and the subject surely will be out of focus.

see pic below:-

Only thing to solve (canon cant do anything) this problem when using wide angle len is to zoom-in, lock ur focus than zoom-out and capture.

Wish Canon be able to solve it when time comes.

PS: No matter what's the problem, Canon Customer Service is :thumbsup:

 

[freelancer]

Me & friend bring to Canon Service Centre. Was told alots user feedback same problems.

After taking hours to check through and they even get back to Canon HQ. The Answer is... all 20D have same problem. Just that some user still yet to notice it.

First time I am hearing this technical explanation. Still trying to figure out if this is for real. Based on what I know, it cannot be true as the 20D sensor is the same size as 10D and 300D. Sorry

 

[ant]

Some feed back in dpreview...

http://forums.dpreview.com/forums/read.asp?forum=1019&message=11028135