[t502kg]

Dear all Ching, I am not saying which lens is good or bad, but i really don't know if this is called "走焦". Recent I have bought EF 24-70L to replace my EF-s 15-85 for 7D, but I found they have quite obvious different performance when comparing nearly in all range, (I have not tried apple to apple for other range yet, just go through with my Camera LCD), especially in the range of 24mm. let's see some sample i shot today. Again, don't misunderstand my intention, i am just asking for help if you guys has experience on this, if it is the problem of "走焦", I will take the 24-70 to canon CS for calibration. Thanks in advance and see if you have any idea on below.

24-70 original


1585 original


2470 crop


1585 crop


By the way, how to check by yourself if the lens have "走焦" at home?

[t502kg]

just post my text again since the AD has covered it.

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Dear all Ching, I am not saying which lens is good or bad, but i really don't know if this is called "走焦". Recent I have bought EF 24-70L to replace my EF-s 15-85 for 7D, but I found they have quite obvious different performance when comparing nearly in all range, (I have not tried apple to apple for other range yet, just go through with my Camera LCD), especially in the range of 24mm. let's see some sample i shot today. Again, don't misunderstand my intention, i am just asking for help if you guys has experience on this, if it is the problem of "走焦", I will take the 24-70 to canon CS for calibration. Thanks in advance and see if you have any idea on below.
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[t502kg]

Oh! forgot to list out the metadata. the original shots were the same taken by 24mm f/4.0, 1/800.

[dj169]

So, which one was better ? I think it more than 90% same.....but nothing "out focus".

[Marksman01]

Need a focus test chart and tripod for the test. Also need to test in different aperture and distance.

[pongyee]

in my opinion, you have magnified the pictures too much so both of them couldn't give you sharp images.

to test whether your lenses focus correctly, you better take pictures with objects line up towards your lenses (e.g. 9 poles in a line) so that you can see whether the selected object being shot at is in focus or not, if the object in front of (or at the back of) the selected one is in focus but not the one you choose, then it is so called "走焦".

there are special charts designed for testing purposes, but i can't find a link at the moment.

if your lenses can't be focused at the infinity end, then it is the problem of the infinity setting in the lenses.

i am just a photo lover, not a master, but hope this could help.
　

[stanleyau]

Hmm... from my experience on 50D, auto-focus in Liveview mode will always be accurate even if the lens have 走焦 problem (believe they're using different focusing technology) So you may try to shoot one with normal AF mode and another one in Liveview mode, i think it's the easiest way to test for 走焦...

Correct me if i was wrong :)

[pongyee]

stanley,

oh yes the 2 modes r using different focusing system,

even if the live-view may focus correctly, but the ovf is still the priority choice for taking pictures, do u agree that?

happy shooting! ^^
　

[t502kg]

Thanks all chings' comment.

Thanks marksman01 ching, in such case, I rather bring to the CS for testing....haha!

Thanks Pongyee ching, i tried out for another range, seems like at the 70mm@infinity they are pretty much the same. I think it is something do with the 24mm@infinity, or is it I have to admit that the sharpness of 15-85 is monster level??? Better than L??

Thanks. Stanley ching, i tried out the live view mode for focusing, but pretty much the same as did in the ovf.

Here is the weird case, i just came back for testing on street.

Original 2470


Original 1585


So far nothing wrong, right? Here comes the weird thing below, what happen to the “五萬呎商場包羅萬有"???? Is it out of focus or the problem of sharpness?????? Both original photos focus to the building center point, same aperture, same distance, same shutter speed, same exposure.

2470 crop


1585 crop


So 15-85 wins right? Nahhh..... the most weird thing has not come out yet!! How about this one? 24-70L is now sharper than the 15-85 when comparing at the building near roof!!! i am confused now............吾通個焦真係識走？？？

2470crop


1585crop


Can someone give a clue............? Many thanks!!!!!

[stanleyau]

pongyee Ching, yes of course i agree with you that ovf is the first priority for taking picture but i was just suggesting a way to t502kg Ching for 走焦 test...

t502kg Ching, first of all, 15-85 is really a superior lens in term of sharpness, i did some comparisons with some of my prime lens before. But, your above test was a different case. The top of the building is at the very edge of your original photo, which is also at the very edge of 15-85 (ef-s), but it is relatively more "center" in the 24-70 lens (ef). I believed that's why 2470 is sharper than 1585.

hope my comment could help you :)

Cheers

[t502kg]

Thanks Stanley, I end up find out it is definitely the OOF problem, I tried adjusted the 鏡頭對焦微調by -5 degree, seems like the problem solved. But I will bring to canon CS for calibration tomorrow. 對於原廠鏡也有走焦問題，實在有點失望！而且聽其他師兄講，有時cal完都未必滿意.......苦惱中！
Thanks all Ching again!

[pongyee]

t502kg,

it seems to me that the last 2 original pictures u took had the following phenomenon:

1) the 2470 was focused on the main object (the tall building);
2) the 1585 was focused at something b4 the tall building;

thus the depth of field (dof) for the 1st pic didn't cover the banner in the foreground but the dof cover it as the focus was a bit b4 the building.

however, i am not sure if i guess it correctly.

[t502kg]

Thanks for your comment pongyee, I am glad you are still concerning my problem. But as matter of fact both the original pictures were taken at the center point focus at the center of the building, so if they came out with different DOF at same aperture 4.0, then one of the lens might go wrong, my guess is the 2470 as i did lots of sample last night, the 2470 can't even focus at the distance of 1.3m object, you won't notice that until you crop to about 200% and it will be quite obvious when comparing to the 1585. But when i offset the focus in the 7D body by minus 5 ~ 8 degree, the problem solved. I eventually bring my brand new 2470 to TST canon CS for repair just this afternoon, hope their technician can find out the problem and fix it for me......
Thanks again!

[pongyee]

it's ok, t502kg, don't mention.