Canon 50mm 1.8 focus problems.

[nessiemac]

Evening all.

Noticed a few issues lately when using the above lens on my Canon 550d. Most of the photo's turn out really nice and sharp but i sometimes have the occasional ones that just are plain not in focus at all. Take the pics below....

1



2



Both photo's taken in aperture priority and both at f5.6. No 1 was 1/125th ss and no2 was 1/80th ss.

No 2 is just not sharp at all and today about 5% of the photo's had the same problem.

I had some beautifully sharp ones in low light in the church and then some come out like no 2 above. As a newbie to all this am i doing something wrong? Camera shake? Lens issue? Very annoying to get back and see some nice pics ruined!!

Cheers

[Simpo Two]

Can't really judge from resized versions; you'd need to post a link to the full size ones. Resizing throws a whole new bunch of variables into the pot.

[nessiemac]

So would that be uploading to flickr and then hosting them here?

[Simpo Two]

Maybe, not sure as I don't use Flickr.

Were they shot RAW or JPG?

[zcacogp]

Top one doesn't look that bad, from what you can see.

Bear in mind that it has some objects in the middle of the picture that will possibly confuse the AF system. Make sure you know what the AF does, and how it decides what to focus on.


Oli.

[dibbly dobbler]

nessiemac said:

Both photo's taken in aperture priority and both at f5.6. No 1 was 1/125th ss and no2 was 1/80th ss.

No 2 is just not sharp at all and today about 5% of the photo's had the same problem.

I had some beautifully sharp ones in low light in the church and then some come out like no 2 above. As a newbie to all this am i doing something wrong? Camera shake? Lens issue? Very annoying to get back and see some nice pics ruined!!

Cheers

Do the duffers all have a slowish shutter? I wouldn't have thought 1/80 was fast enough - try whacking up the iso or using flash ?

[rottie102]

dibbly dobbler said:

Do the duffers all have a slowish shutter? I wouldn't have thought 1/80 was fast enough - try whacking up the iso or using flash ?

This. That's what's wrong with no 2. The first one seems to be sharp enough for 50mm 1.8 before PP. Check out guy's watch, that's the length that seems to be focussed on.

[nessiemac]

I am shooting in RAW and using single centre point AF.

In the examples above no 1 was an example of a sharp shot. Got the Exif data mixed up so it is as follows...

No 1 is ISO 100. f2.8. 1/125th and pretty sharp.

No 2 is ISO 400. f5.6. 1/60th and not sharp.

The ones i took in the church were all ISO 640. f4 and 1/60th and sharp as a sharp thing!!

[nessiemac]

rottie102 said:

This. That's what's wrong with no 2. The first one seems to be sharp enough for 50mm 1.8 before PP. Check out guy's watch, that's the length that seems to be focussed on.

Using Aperture 3 on the Mac shows my focal point is the left eye on no 1 and the left eye of the lady in no2.

[dibbly dobbler]

nessiemac said:

I am shooting in RAW and using single centre point AF.

In the examples above no 1 was an example of a sharp shot. Got the Exif data mixed up so it is as follows...

No 1 is ISO 100. f2.8. 1/125th and pretty sharp.

No 2 is ISO 400. f5.6. 1/60th and not sharp.

The ones i took in the church were all ISO 640. f4 and 1/60th and sharp as a sharp thing!!

Simpo knows about 1,000,000 times as much as me about this but for my 2p worth 1/60th *might* be ok if the subjects are still but in general you'd want to get the shutter a good bit faster or you're risking motion blur

[nessiemac]

dibbly dobbler said:

Simpo knows about 1,000,000 times as much as me about this but for my 2p worth 1/60th *might* be ok if the subjects are still but in general you'd want to get the shutter a good bit faster or you're risking motion blur

So,i was using aperture priority with f5.6 to get a good depth of field and ISO on Auto it still set a lowish shutter speed. It didn't seem that dark in the pub conservatory and was sunny out so assumed that would give a much higher shutter speed?

It just seems odd as i have some group photo's taken outside today as well and tack sharp at ISO 160. f8 and 1/60th which surely is very slow for a sunny day?

Just checking some photo's from a cyclocross race last week on a sunny day and no problems with most pics at ISO 100. f3.5 and 1/500. So maybe i just assumed it was sunnier than it was and not paying enough attention to SS when clicking away??

Edited by nessiemac on Sunday 23 October 22:42

[dibbly dobbler]

I can sympathise as I think it's just one of these things which is inherently tricky to get the hang of.

One possible bit of advice would be to check how much dof you actually need (try dofmaster) - I would have thought you could open up the lens a lot more than f5.6, this would help.

Also I would go with manual iso and just whack it up to 500/600 in low light and see what shutter speed it gives you - it takes one of the variables out of it so might make things clearer.

I'd love to know what settings the good guys use for this sort of thing (ie Av, Tv, manual, a mixture) ?

[nessiemac]

dibbly dobbler said:

I can sympathise as I think it's just one of these things which is inherently tricky to get the hang of.

One possible bit of advice would be to check how much dof you actually need (try dofmaster) - I would have thought you could open up the lens a lot more than f5.6, this would help.

Also I would go with manual iso and just whack it up to 500/600 in low light and see what shutter speed it gives you - it takes one of the variables out of it so might make things clearer.

I'd love to know what settings the good guys use for this sort of thing (ie Av, Tv, manual, a mixture) ?

Cheers DD and everyone else

To be honest auto ISO is one less thing to worry about but will get it off auto and have a play and not just assume that as it's a nice day the SS will be sufficient. I didn't think off it as one less variable but one less thing to cock up but as you say it takes away another control i (don't) have!!

Thanks again all.

edit. Just had a look at dofmaster and that really explains and helps a lot instead of guessing what i need. Lots more reading!!!!!

Edited by nessiemac on Sunday 23 October 23:04

[Rinko]

nessiemac said:

Cheers DD and everyone else

To be honest auto ISO is one less thing to worry about but will get it off auto and have a play and not just assume that as it's a nice day the SS will be sufficient. I didn't think off it as one less variable but one less thing to cock up but as you say it takes away another control i (don't) have!!

Thanks again all.

edit. Just had a look at dofmaster and that really explains and helps a lot instead of guessing what i need. Lots more reading!!!!!

Edited by nessiemac on Sunday 23 October 23:04

I seem to recall that the Auto-ISO will only only go up to 400 by default, so might still not give you enough flexibility to keep the shutter speed up. Ultimately IMHO, you are better off with a sharp "noisy" image than a blurry one. Just for reference, I regularly bump my 30D up to ISO 800 to keep my shutter speed up. Removing noise in PP is always an option!

As I'm sure you've now realised, you could have got away with a far wider aperture in your second shot. Particularly as both couples faces (and eyes - which is where you would focus) are fairly close to being on the same focal plane. This would mean both could be in focus even shooting very wide, even wide open as f/1.8 on a 50mm at 1m from the subject will give you a 10cm DoF.

Edited by Rinko on Monday 24th October 12:55

[Irrotational]

I have this lens and I suspect my copy is faulty - in all sorts of conditions - with good shutter speed! - I get the odd blurred photo...maybe 10% or so.

I have the 18-135mm kit lens as well and it never gives duff results

One thing people try, to test the lens, is try focussing on something very close, and then focus on the target, and try focussing far away, and then focus on the target. You may get different results one sharp and one not.

I am not an expert by any means - just read a few forums with slightly dodgy focussing on this lens

[cornet]

nessiemac said:

I am shooting in RAW and using single centre point AF.

Did you focus then recompose the image. If you did then this could explain the softness. Could also be camera shake, can't tell without seeing the full res versions.

[Simpo Two]

It might be wise to attempt to distinguish between 'out-of-focus' and 'camera/subject movement', as they are entirely different things.

[nessiemac]

Simpo Two said:

It might be wise to attempt to distinguish between 'out-of-focus' and 'camera/subject movement', as they are entirely different things.

Two different things maybe but to my eye how can I learn how to tell the difference?
And to the above question yes I would have focused and then moved the camera with shutter half pressed.
Thanks again to all who have replied.

[RobDickinson]

nessiemac said:

Two different things maybe but to my eye how can I learn how to tell the difference?
And to the above question yes I would have focused and then moved the camera with shutter half pressed.
Thanks again to all who have replied.

Generally if there is missed focus then SOMETHING is sharp/infocus.

If its camera shake then everything is a bit blurry.

IMO at f5.6 its unlikely to be caused by focus/recompose issues, this happens with vast apertures only, stopped down to f5.6 and at this range the DOF is unlikely to have moved significantly.

Remember also that 1/focal length doesnt work so well on crop bodies with high pixel counts, 1/focal length * 2 is a good minimum depending on HH technique.

[Simpo Two]

RobDickinson said:

Generally if there is missed focus then SOMETHING is sharp/infocus.

If its camera shake then everything is a bit blurry.

I'd add 'directional' blur, or a smearing effect - logical if you think about how it's created. Usually sharp in one dimension.