Issue with lens?

Skipraider

Skipraider

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I bought a Canon 50mm 1.8 at the beginning of the year and ever since then i have been getting patchy results with it.

The problem has been that the focusing just didn't seem to be right on some images, and they were blurred completely, especially around 1.8f. I was putting this down to user error and thinking maybe the shutter speed was too slow (even though i thought it should be fine) or just a ridiculously small DOF of about 1 pixel :bonk: as some pictures were fine and sharp where i wanted. I have been keeping away from 1.8 and if i use it at >2.5f it seems much better.

However i thought i'd do a quick test of focusing on a number on a ruler.

For all the images below i have focused on the actual number 6, have a look at the results and tell me your thoughts. All photos were taken at speeds above 1/400 with automatic focus on the 6.

Lens issue or user error?

focus2.jpg


Focus1.jpg


focus3.jpg


Focus4.jpg


Focus5.jpg


Focus6.jpg


Continued...
 
Focus7.jpg


Focus8.jpg


Focus9.jpg


Focus10.jpg


I have no such issues with my 17-85:

1785Focus.jpg


1785Focus2.jpg



As you can see the results are not great.

Do you think this is a lens issue or something i'm doing wrong?

Thanks :)
 
Hate to say it but i think it is you.
In some of the pics where the ruler is at an angle the closest bit to you is in focus. What AF mode are you in? And have you tried MF?
The DOF is very shallow at F1.8 and I think (i could be talking through a hole in my head) is at close focusing distance it is harder to keep the camera perfectly steady where the slightest rock forward or backward would blow your focus. Have you tried on a tripod with self timer or remote?


HTH

Tony

Hopefully somebody who actually knows what they are talking about will be along shortly.
 
Big Tony said:
Hate to say it but i think it is you.
In some of the pics where the ruler is at an angle the closest bit to you is in focus. What AF mode are you in? And have you tried MF?
The DOF is very shallow at F1.8 and I think (i could be talking through a hole in my head) is at close focusing distance it is harder to keep the camera perfectly steady where the slightest rock forward or backward would blow your focus. Have you tried on a tripod with self timer or remote?


HTH

Tony

Hopefully somebody who actually knows what they are talking about will be along shortly.
Click to expand...


Hi Tony, thanks for your reply.

I was using 'one shot' AF mode. When i was focusing, i focused using the centre point, and the point looked like it was focused in the viewfinder.

Your right in saying that some bits closest to me were in focus, but i thought the whole point of using the af points was to get the point that you wanted in focus?

I haven't tried MF as all of it would be blurred then :lol:
 
The idea of photographing a ruler scale is that you shoot from one end (not the flat way) so you can use the scale to see if it is front or back focussing, and by how much :thumbs:
 
Is it possible that you may be moving back and forwards ever so slightly at F/1.8 ?

The amount of the subject in focus at that aperature is very small indeed.

Just a thought :)
 
You must do this kind of test with the camera mounted on a tripod or on something where it's not going to move. Also use mirror lock up if you have it on your camera.

At f1.8 if you hand hold and sway just a little it will be out of focus pretty quick and easily at the angle you are shooting the ruler at.

Let's hope it's user error and not lens error. Far cheaper to get your method right :D:thumbs:
 
Thanks for the good advice guys, i will be pulling out the tripod, printing the chart off and giving it a go later on.

I'm actually hoping it's a dodgy lens as i've ended up with completely oof portraits before :p (which i'm sure would have been fine with the 18-55 - although it does have IS... hmmm).

Maybe i need to use a tripod more?
 
AndyWest said:
You must do this kind of test with the camera mounted on a tripod or on something where it's not going to move. Also use mirror lock up if you have it on your camera.

At f1.8 if you hand hold and sway just a little it will be out of focus pretty quick and easily at the angle you are shooting the ruler at.
Click to expand...

Yup, such a test is meaningless if it's not done with a tripod. It's also meaningless if there isn't a clear, isolated target for focussing. The actual AF points are significantly larger than the rectangles shown in the viewfinder. So when you 'focus' on the '6' the actual AF point will be covering a lot more of the image. The AF system will lock onto the closest area of contrast covered by the AF point.
 
What happened to all the replies :thinking:

Have i been dreaming about being on this forum? :cuckoo:

Anyway, i gave the focus chart which i dreamed up a try and funnily enough it was just me being a numpty :bang:

Thanks for all the help guys, you stopped me from making a fool of myself (in person anyway, not on here!)

Chart:

focuschart.jpg
 
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