tell me if i'm goofin up (70-200 f/4?)

[summerwind4]

right now i'm pretty ecstatic about my new 70-200 f/4 L, but i need some help, in the following shots, does it look like there is back focus problem at 70mm?
the long end is sharp as ever, but for some reason i get mixed results at 70mm, for instance, this one at f/4 (focused on the hydrant for all 3)

am i focusing at the wrong areas?

http://www.pbase.com/summerwind4/image/45453972

then at f/10

http://www.pbase.com/summerwind4/image/45454042

then at f/4 from another angle (aimed a little lower on the hydrant)

http://www.pbase.com/summerwind4/image/45459010

next i shot a street light at 200mm

http://www.pbase.com/summerwind4/image/45454847

then at 70mm

http://www.pbase.com/summerwind4/image/45454511

this may have been from the focus square being over a percentage of the light?

other test shots are at

http://www.pbase.com/summerwind4/70200f4l_tests

i have no problem sending this one in for a calibration as it is super smooth and like i said, the 200mm end is awesome.

thx in advance for those that join in to help:)

[kram]

My 2 cents - the shots are really wide to test for focus. I would look at shots where there are items whose edges can be clearly checked - tree leaves, hair (pets), fences etc.

And a series of objects that can be checked whether its in focus or not would easily identify back/front focus issues.

[summerwind4]

something like this? focus was on the string of the bottle in the center

http://www.pbase.com/summerwind4/image/45459051/original

or this? focus point was on the blue box

http://www.pbase.com/summerwind4/image/45455882

[tim]

You can't judge focus accuracy with random shots, you need to use a focus test chart (http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm), a tripod, and a cable release with mirror lockup/the timer. Do that and you can work it out for yourself, or we can help interpret the results.

Anyone who draws a conclusion from the posted shots probably shouldn't be believed.

[summerwind4]

You can't judge focus accuracy with random shots, you need to use a focus test chart (http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm), a tripod, and a cable release with mirror lockup/the timer. Do that and you can work it out for yourself, or we can help interpret the results.

Anyone who draws a conclusion from the posted shots probably shouldn't be believed.

Excuse me??

i didn't post those to be stupid or deceiving, is that what you are implying?
my past forte with Canon gear has never had me tie up my precious time with test charts and such so i thought the samples i posted were genuinely helpful in my case.
or do you mean is someone posts a comment?
i just like to shoot pictures, and want to know if these samples (bad as they may be) are just a result from not understanding my equipment.

[tim]

I'm not calling you stupid at all, if that's how you understand my post I apologise. What i'm saying is you can't judge how well a lens focuses in uncontrolled conditions, as there's too many variables. You need a focus chart or something similar, a tripod, and preferably a way of triggering the camera that won't shake it to do a proper test.

My final comment came across a bit harsh, but I stand behind the idea. ie anyone who comes to a conclusion based on a less than complete set of data shouldn't be trusted to come to a valid conclusion.

[summerwind4]

Gothcha!!..........i guess i took it wrong initially......sorry.
yes, the more i look at the shots, the more i realize that they don't prove much at all.

good thing is i am off this weekend for 4 days. i guess i'll take the time to do it right.
i have this link for doing the tests, is this ok?

test charts

http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

[tim]

Yep that link's fine, most focus test that include a target parallel to the sensor and a ruler that goes front to back are fine. Shouldn't take too long - half an hour once you get the test chart made maybe :)

[summerwind4]

thx Tim.