Camera, lens or operator?

The AF sensors are located in the camera, and measure contrast based on the image bounced down to them (they're in the bottom of the mirror box, right behind the lens mount). The rest of the process is a feedback between the camera, which says "go this way 3 clicks" and the lens, which says "OK - done that". Somewhere along the way, the camera will say "Hold it!"; the lens might,or might not, stop immediately. It's also possible that the light path to the AF sensors is just a little off, or that an unfortunate choice of target can give a false impression of focus. So basically, it's a feedback mechanism between the camera and the lens, where both play a role.

Graham have you ever tried macro photography with tubes? The slightest movement is enough to throw off the shot and that includes pushing the shutter verses a cable release. Just trying to help by suggesting to eliminate all the variables that could cause a problem.

blue_max wrote:
I've got to admit Jon, that I thought you were referring to the camera's batteries and not the subject. that did sound extreme!

Just to be clear though, I had the camera on a table and just pressed the focus button and let go. There is NO chance that I have focussed on the wrong battery. I obviously can't describe everything I did or the post would be a novel and no-one would read it. So far, the response has been that it has been my technique (not that I am beyond reproach in this are), but I still am interested to hear if anyone knows whether auto-focus is a function of the lens or camera, or both.

I hear what you are saying, but it can't be that flakey can it?

Graham

Thanks for the technical explanation Jon,

mrclark321, I have actually with my old hasselblad and tubes. I do realise that the 1.4 gives a narrow depth of field at 1.4

My test was from about four feet away and the focus was off about three inches. I am happy to agree that the camera may have moved a small fraction of a millimetre when I pressed the focus button. This is a real world scenario and nobody alive could hand hold to a greater degree of accuracy, so it's an unuseable lens at that aperture perhaps.

Graham

I have a similar problem with my 20D, images just don’t look like they are properly in focus (most of the time) I have downloaded the focus test chart and will be running some tests tonight with various lenses I have.
So far I only have the kit lens and some older AF lenses from my old EOS 650, namely a 35-105 and a 70 – 210.

This thread was an interesting read and this is my first post

Cheers

C

Welcome to POTN

EOSAddict wrote:
Welcome to POTN

Thanks for the welcome!! was excited that the mail notification was going to be the answer from God about my focus problem.....

You can view some of my out of focus problems here (note that these are the better ones or should I say closer to being infocus) CLICK HERE

im a bit pee'ed off as I thought I was buying the best camera under the 5D

But rest assured that come 5pm I will be shooting home with my printed test sheet to test the focus thing!!

C

You might find your images soft straight out of the camera if you are used to Dig point and shoot, are you shooting RAW or JPG images? if JPG, what parameter settings are you using?

You may need to sharpen your images in Photoshop or it may be that the quality of the 20D image is exposing a weakness in your lenses.

Good to see a Swiss member, havn't been there for too long (5 yrs last visit ) Have been a frequent summer visitor to Grindelwald and Lucerne for about 30 yrs, but never made it to Zurich.

EOSAddict wrote:
You might find your images soft straight out of the camera if you are used to Dig point and shoot, are you shooting RAW or JPG images? if JPG, what parameter settings are you using?

You may need to sharpen your images in Photoshop or it may be that the quality of the 20D image is exposing a weakness in your lenses.

Good to see a Swiss member, havn't been there for too long (5 yrs last visit ) Have been a frequent summer visitor to Grindelwald and Lucerne for about 30 yrs, but never made it to Zurich.

im not SWISS !!! im a Britt and proud of it (but would never move back to the UK)

thanks for the info, now I am shooting in RAW and if you check the link in my sig you will see some of the results. I have been selecting the setting P and most of the time selecting a WB program that I think (have read) is best. shooting in JPG produced much the same results. Also been trying to use the kit lens more for worry that it was the camera that for some reason didnt like the older EF lenses I have.

Trouble is I have to sharpen 99% of the images after they come off the camera, I have even tried to shoot JPG and change the sharpness in the camera functions to improve this but no luck! If I cant get this sorted I will pack all the kit into a Peli case and send it back to Canon to check out. though I love the camera, feel, weight, battery life.... just wish it would take a sharp picture!

Cheers

C

Oops! Just read your entry in the 'who am i' thread, sorry! Love the pics in your photoblog, v nice!

I noticed you mention CF 4-1,. but I did nopt see if you mention Single shot or AI Servo. I am guessing maybe AI servo as it's the natural choice with 4-1??

One thing about AI Servo that gets over looked,.. is it keeps focusing.. and often changes from good to bad as you hold it down. Vice versa,.and more so ith some lenses than others,. it will give the AF o-kay signal sometimes long before AF is really o-kay.

If using AI servo and CF 4-1, make sure your locked down on a tripod and try holding the * button while viewing.. see if the AF lock "corrects" itself....

Don't try this test in low light...

To me it looks like the Lens AF is the culprit,. I'm sure about the 50mm 1.4 but my 50 1.8 was the worst most inconsistent focusing lens i have ever used since I started shooting DSLRs... it Never acheives correct focus on the first try and holdingthe * for some time was allways required beofre my view in the viewfinder would agree with the focus confirmation that I wa sbeing given.. during that time I could watch it hopping all over the pa;ce just out of focus... front and back before it would (usually) finally acheive real focus.


Lastly,. I think the Battery test is as good as any chart,. so lonmg as enough light is provided fro the camera to do it's thing.

Thanks CDS, but unfortunately it was one shot, I am sure your detailed explanation will be worth knowing though. There seems to be some preference for the 'other' tests, but focus is focus.

The 50mm 1.4 is supposed to be better, but maybe I was just unlucky. I have tried another test, but it never seemed to get very light here today, so I am not sure of the rusults (it seemed to perform better than the other day though).

I feel rather better if it's just the lens. Four lenses and a body would be rather costly to sort out I am sure.

I'll post back if I reach any conclusions. Meanwhile, any more thoughts are more than welcome.

Graham

Well I rushed home and used the test sheet as mentioned above and guess what? Perfect focus! Tried a few shots to see if it was a one off, even turned the camera off, changed settings and reverted back to as the test says to set up. Still perfect focus!

So it must be me! setting up for my shots and the way im using the camera! back to the books!

BTW: and off topic im got an interesting answer on my blog to can you guess that this is.... link below

C

Another question I have on this subject is that if I shoot in JPG and not RAW and I set the parameters to add more sharpness will this spoil the image for example if I wish to do a heavy crop on an image will doing this make it more noticable (that is if the image was in focus in the first place?)

Thanks

C

In my humble opinion the test is only valid if the camera is locked down on a tripod.

It's easy to sway an inch and that would be death to focus at this range.

Was it tied down..? if not, try again...

Baz

yes it was locked onto a good Manfrotto tripod and im happy with the result, but not happy with my camera skills!

C