Is this what is known as back focusing?

L

LumixNoob

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233
Name
James
Edit My Images
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I just got the Canon 24mm STM 'pancake' lens and something isn't right. Here are some examples of the focus problems I'm having - the first is the 24mm pancake, the second my 15-85 @ 24mm, exact same shot/focus point:

IMG_5147 by James Howard, on Flickr

IMG_5146 by James Howard, on Flickr

Here are screenshots from Zoombrowser with focus points highlighted:

24mm pancake by James Howard, on Flickr

15-85@24mm by James Howard, on Flickr

I'm guessing I need to return it.
 
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Certainly looks like the 24mm is focused behind the focus point. The Nivea seems sharper.
 
Is the aperture the same for both shots? Perhaps the pancake needs stopping down a bit for better sharpness, also it looks very close to the subject. For me the 1st cropped picture is sharper on the book than the second, so it maybe back focusing a bit. Your camera may allow you to adjust this.
 
Try taking some test shots of a ruler at 45 degree angle, or something similar. You can then easily see where the sharpest focus is.
 
Swanseajack said:
Is the aperture the same for both shots? Perhaps the pancake needs stopping down a bit for better sharpness, also it looks very close to the subject. For me the 1st cropped picture is sharper on the book than the second, so it maybe back focusing a bit. Your camera may allow you to adjust this.
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Yep, same aperture - f5.6. The 24mm is a bit soft at f2.8 but otherwise pretty sharp. I also tried a few different distances, but the pancake can focus down to about 15/16cm.
 
Definitely focussing behind the focus point, although glass isn't the ideal thing to focus on.

As above try the grid at 45 degrees, or even the 5 battery test can give you some inducation. Plenty of info on the web, and free charts to download :)
 
Your test shots have been taken in a dimly lit room from the looks of it. This is not conducive to getting the best focus performance out of your camera (and lens). You are also trying to focus on a transparent object, which is not the easiest target for the autofocus system to lock on to. It would make more sense to use the book or the writing on the Nivea bottle as the target.

I would try to take several test shots from the same distance, preferably from a tripod, re-focusing each time, and preferably in good light (daylight outdoors would be best). I would only be worried if I could reproduce the misfocus over 50% of the time.
 
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James, any higher model will have an focus adjustment.
Maybe you should try to find in the manual if your camera
has the feature before returning the lens!

I owntop of the range gear and I have to fine tune the
focus on all three bodies combos with 16 lenses every
now and then… normal.
 
The light is a bit dim, but both lenses focus straight away both with and without flash. I've just tried the 5(well 4) battery test and got a 100% hit rate with the 15-85 @ 24mm and a 100% miss rate with the 24mm. It definitely doesn't focus properly.
 
Kodiak Qc said:
•


James, any higher model will have an focus adjustment.
Maybe you should try to find in the manual if your camera
has the feature before returning the lens!

I owntop of the range gear and I have to fine tune the
focus on all three bodies combos with 16 lenses every
now and then… normal.
Click to expand...

If I do that though, won't it throw out the focus on my other lens(es)? The 15-85 is bang on every time.
 
Bodies with fine-tune capabilities tend to be able to save a number of lenses.
 
LumixNoob said:
If I do that though, won't it throw out the focus on my other lens(es)?
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Of course not!

As I fine tune all my bodies with all my lenses, it would
be ridiculous to loose anything!

All my cameras can remember up to 20 different lens
and their respective settings. If yours can fine tune, it
will remember too!
 
I don't think my camera has it anyway Kodiak. I've been through the menus and can't find anything.
 
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What make is it?
 
Canon (600D). I bought it used and don't have the manual. I did a quick search though and it appears only the 10 series and above models have it (60D etc.).
 
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If you change the lens, you might be facing the same problem.

I cannot help you more since I've not been in that situation with
the equipment I got… sorry!
 
Sorry, 600D doesn't have AF micro adjustment. Where did you buy the lens? Any mates with a Canon camera you could try it on?
 
paulcamcas said:
if it isn't good, back it goes at their expense.
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•

That raises the question:
"How many time do you want to go through that circus?"
 
I might end up going for something else anyhow. Other than it's portability it doesn't offer much over the 15- 85 @ 24mm. Plus I've got accustomed to having a distance window.
 
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Kodiak Qc said:
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That raises the question:
"How many time do you want to go through that circus?"
Click to expand...
Why is it a circus? It's a long way to a decent camera shop.

By the way, I'm sure you have been asked before but what is the dot (sometimes dots) about?
 
LumixNoob said:
I might end up going for something else anyhow. Other than it's portability it doesn't offer much over the 15- 85 @ 24mm. Plus I've got accustomed to having a distance window.
Click to expand...
Have you checked which focal lengths you use most on your zoom? That might be where a prime would do most good. Or, if you like the zoom, an upgrade to a better one might be worthwhile.
 
paulcamcas said:
Why is it a circus?
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I have a local dealer where I get all I want to try and test.
And this is where I buy… at internet prices!

Support your local dealer!
 
My local (45 minutes away) dealers are big chains with limited stock who have no claim on my support.
 
I'd get a replacement from Amazon too, I've done it and it's really no hassle at all. Much less hassle than the hour round trip to me nearest camera store.
 
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