Canon 50mm F1.4

G

Grumps1974

Messages
1,602
Name
Martin
Edit My Images
No
I have the above lens and I am seeking advice.

The lens auto focuses very well at F4 and above. However I find that I only get in focus pictures occasionally at apertures below this. As I move increasingly toward F1.4 the percentage of in focus pictures gets less. I do get some pictures in focus at these apertures but it is very hit and miss. I know that the AF mechanism works so I don't think the lens is faulty. Having googled this it seems a common problem for owners of this lens.

Has anyone got a technique they can recommend that would enable me to shoot a greater percentage in focus at wide apertures?

Many thanks
 
Last edited:
Hi Martin,

Every lens works better and gets sharper stopped down a bit. So, your 50mm will have better image quality at f4 than at its maximum (or near maximum) aperture.
Also, focusing at f1.4-f2.0 is much more challenging that at smaller apertures, because of the bigger depth of field (at smaller apertures).

If you want to make some tests, you have to shoot with a tripod and a fixed target (in good light), at different apertures, and check if the lens is focusing where it should.
Your camera+lens may need to be calibrated. Does your body have MFA?

That said, my 50mm f1.4 on my 5Dc (calibrated by Canon) is sharp at f1.4, sharper at f2, very sharp at f2.8 and incredible sharp at f4 and beyond!
But you have to nail focus at the bigger apertures. ;)

--
P
 
Last edited:
Hi Luis

Thanks for your comments.

I think I might not have explained myself clearly. Perhaps my original choice of the word sharp was wrong and misleading here.

This is not a question of front focussing or back focussing or the picture being slightly soft. It is more a situation where only a few photos at wider apertures are in focus but a lot more are clearly completely out of focus. This problem goes away when shooting at F4 and above when all shots are in focus.

As I said googling this suggests this is not unusual on this lens. Research also suggests the lens AF mechanism is very sensitive to even slight knocks. However where the lens has been knocked it suggests all F stops are affected. With my lens only F1.4 to F2.8 suffers focus problems.
 
Last edited:
If the lens is a bit iffy maybe all you can do is give it the best possible chance of success. Assuming that your technique is as good as can be (no moving when taking the shot...) other than that maybe all you can do is try to aim at an area of your subject that gives the best chance of the lens acquiring focus.
 
Grumps1974 said:
.... Research also suggests the lens AF mechanism is very sensitive to even slight knocks. However where the lens has been knocked it suggests all F stops are affected. With my lens only F1.4 to F2.8 suffers focus problems.
Click to expand...
The lens will always focus at f/1.4 (irrespective of your chosen aperture) and then it stops down before the shutter opens for the shot. It's hard to see a scenario where f/4 is good and f/1.4 isn't other than the error being masked by the increased DoF at the smaller aperture.

Bob
 
Martin,

1. what body are you using?
2. are you using central focus point or "multi" focus points?
3. are you shooting mainly moving or fixed targets?
4. can you make a test with a fixed target, tripod and remote shutter, using several apertures?

--
L
 
Thanks for all your comments.

To develop on this

I have been using a 6D (but get the same results with an EOS-M). All shots have used the central focussing point. All shots are of static targets. If I can master uploading photos the following demonstrate what is happening. All these photos are crops from RAW originals but no post processing was done. The originals were taken from exactly the same point of view. The first series were taken using AF. The second (file names have suffix 2)were taken after auto-focussing at f5.6 and then switching to manual focus to lock the focus point. All were taken focussed on the D of the central battery. To save uploading lots of photos I have uploaded photos at f5.6, f2.8 and f1.4. You will see that there is a progressive deterioration from 5.6 to 1.4. Although I have not uploaded f4 and f1.8 this gradual deterioration can be seen in them as well.
 
Last edited:
Last one.

Just to add one other point. Prior to focussing on the batteries I pointed the camera at the sky and ensured that the AF was not focus locked on anything. Then I focussed on the battery.
 
Last edited:
I'm not 100% sure, perhaps others can comment, but the f1.4 shots look in focus, just soft. Your copy may not be quite right wide open.
 
Believe me at f1.4 they are not soft. The one posted is one of the better ones. You should see some of the others.:(
 
I don't think that this is a focus issue at all. I think that the images seem to be showing that the lens has an unusually high amount of coma.
Why?....ah, that's a good question. My suspicions are that one of the elements is skewed slightly or that one of the groups is separating. Stopping down will reduce the amount of off axis light and reduce the coma....making the image seem sharper and in better focus.

Grab a bit of black card or paper and cut a hole in it (about 1cm diameter should be fine). Hold the card in front of the lens and take one of your test shots (the batteries) with an aperture of f/1.4 and repeat the test at the same aperture but without the card.

Bob
 
Canon Bob said:
I don't think that this is a focus issue at all. I think that the images seem to be showing that the lens has an unusually high amount of coma.
Why?....ah, that's a good question. My suspicions are that one of the elements is skewed slightly or that one of the groups is separating. Stopping down will reduce the amount of off axis light and reduce the coma....making the image seem sharper and in better focus.

Grab a bit of black card or paper and cut a hole in it (about 1cm diameter should be fine). Hold the card in front of the lens and take one of your test shots (the batteries) with an aperture of f/1.4 and repeat the test at the same aperture but without the card.

Bob
Click to expand...

Thanks Bob

I will give this a go tomorrow and post the results.
 
My 1.4 was fine for ages when I had it. Then it started not focusing all the time, just some of the time and seemed a bit slower. That was the point I should have got it checked by the local camera repairer.

The 1.4 is notorious for responding badly to any pressure on the front of the lens. I had accidentally put pressure on mine it seems. The result is the lens tracking in the lens gets distorted and it then struggles to force the roller along the track as the track is deformed.

The result of my not understanding this or being suspicious of it was that I continued to use the lens, while remaining puzzled. The continued use was what then caused the motor to burn out as it could not cope with repeatedly trying to push the roller along the track. Result was about £180.00 to replace the track and also the motor. Would have been less if I had understood it all sooner as it would only have needed the track sorting.
 
Canon Bob said:
I don't think that this is a focus issue at all. I think that the images seem to be showing that the lens has an unusually high amount of coma.
Why?....ah, that's a good question. My suspicions are that one of the elements is skewed slightly or that one of the groups is separating. Stopping down will reduce the amount of off axis light and reduce the coma....making the image seem sharper and in better focus.

Grab a bit of black card or paper and cut a hole in it (about 1cm diameter should be fine). Hold the card in front of the lens and take one of your test shots (the batteries) with an aperture of f/1.4 and repeat the test at the same aperture but without the card.

Bob
Click to expand...

Hi Bob

Well I have followed your advice and as the photos below (both are crops and taken with MF - no post processing) and show you seem to have hit the nail on the head. I had never heard of Coma before so I have learnt something new.

I have found that from f2.8 up the results are perfectly acceptable with sharpness progressively improving. However although I would not use f1.4 - f2 often it does seem stupid to have a lens that cannot produce acceptable results across its full range. It is a bit like having a car with a six speed gearbox but only ever using four gears. Yes it will work but not to maximum potential.

The questions now seem to be what has caused this effect and what to do about it. Does this mean a trip to my friendly camera technician for a lens overhaul?
 
@Grumps1974

So is this right at the corner of the frame? Is so.. that's pretty normal for a lot of fast lenses. What's it like at the centre? If that's the centre of the frame, then you've got a seriously faulty lens. If it's right in a corner and a severe crop, that's pretty normal for wide open on a fast lens.

Post up the ENTIRE image uncropped so we have context please.
 
Grumps1974 said:
The questions now seem to be what has caused this effect and what to do about it. Does this mean a trip to my friendly camera technician for a lens overhaul?
Click to expand...

It's hard to do anything other than guess at the cause based on a few shots from it but I still suspect an alignment or separation problem. The lens only has one doublet so alignment is more likely. This lens has been in continuous production for 22 years and I'm sure there would have been a MkII long ago if this was the norm...(given its popularity and the fact that 50mm is considered to be "a standard lens").

The coma is visible in the shots you posted yesterday although it's not an easy subject from which to pick it out. A white subject on a dark background and shot on a bright place would highlight it to a larger degree (I've used ping pong balls and sugar lumps...ooops, that sounds like a fetish). A lens hood will always help to reduce the occurrence but it's more severe than simply doing that (if all the fans of this lens are not misguided...I don't own one).

Bob
 
This is the centre of the frame. I see no real value in posting the entire image as you need to zoom in on the batteries to really see the effect I am talking about especially as we can only post low resolution images.

However for completeness they are attached.
 
Last edited:
Canon Bob said:
It's hard to do anything other than guess at the cause based on a few shots from it but I still suspect an alignment or separation problem. The lens only has one doublet so alignment is more likely. This lens has been in continuous production for 22 years and I'm sure there would have been a MkII long ago if this was the norm...(given its popularity and the fact that 50mm is considered to be "a standard lens").

The coma is visible in the shots you posted yesterday although it's not an easy subject from which to pick it out. A white subject on a dark background and shot on a bright place would highlight it to a larger degree (I've used ping pong balls and sugar lumps...ooops, that sounds like a fetish). A lens hood will always help to reduce the occurrence but it's more severe than simply doing that (if all the fans of this lens are not misguided...I don't own one).

Bob
Click to expand...


Don't have ping pong balls or sugar lumps:) but I am sure that I can find something that will substitute so later this morning I will take some more shots and post them.

Thanks to all for their comments - they really are appreciated.
 
Canon Bob said:
It's hard to do anything other than guess at the cause based on a few shots from it but I still suspect an alignment or separation problem. The lens only has one doublet so alignment is more likely. This lens has been in continuous production for 22 years and I'm sure there would have been a MkII long ago if this was the norm...(given its popularity and the fact that 50mm is considered to be "a standard lens").

The coma is visible in the shots you posted yesterday although it's not an easy subject from which to pick it out. A white subject on a dark background and shot on a bright place would highlight it to a larger degree (I've used ping pong balls and sugar lumps...ooops, that sounds like a fetish). A lens hood will always help to reduce the occurrence but it's more severe than simply doing that (if all the fans of this lens are not misguided...I don't own one).

Bob
Click to expand...


Attached are two photos trying as best I can to follow this guidance and with the material available to me. Focus point in both was the "st" in strength on the Korean Ginseng tub.

50mma was shot using MF at 1.4 without any "shield" over the lens and no PP

50mmb was shot using the same focus with the "shield" and no PP was done.

50mmb although still slightly soft seems a lot "sharper" (although the lens does seem in this photo to back focus a little). Incidentally using a lens hood does not seem to improve matters.
 
Last edited:
Firstly, if they were focused manually then the lens can't "back focus", you did!. (Some lenses exhibit a focus shift but this can't occur when using them wide open)

The uncovered shot of the two seems to bolster my coma theory and the smudge heading off the pots in a "northwesterly" direction looks quite severe. Beyond that, it's difficult (for me at least) to be any more definitive just by looking at some low resolution images and not having the thing in my mitts to go further. I suppose that it's possible that some kind of light leak might give a similar problem although unlikely with this type of construction.

Sorry that I can't help further.

Bob
 
Canon Bob said:
Firstly, if they were focused manually then the lens can't "back focus", you did!. (Some lenses exhibit a focus shift but this can't occur when using them wide open)

The uncovered shot of the two seems to bolster my coma theory and the smudge heading off the pots in a "northwesterly" direction looks quite severe. Beyond that, it's difficult (for me at least) to be any more definitive just by looking at some low resolution images and not having the thing in my mitts to go further. I suppose that it's possible that some kind of light leak might give a similar problem although unlikely with this type of construction.

Sorry that I can't help further.

Bob
Click to expand...

It is quite possible that I back focussed - my eyesight isn't all it was! I much prefer AF - cameras are much better at getting focus right than I am.

It looks like I am going to have to talk to my friendly local camera technician for a repair job. At least I know he will do a good job and will not charge me a fortune.

Thanks for all you help.
 
Canon Bob said:
Firstly, if they were focused manually then the lens can't "back focus", you did!. (Some lenses exhibit a focus shift but this can't occur when using them wide open)

The uncovered shot of the two seems to bolster my coma theory and the smudge heading off the pots in a "northwesterly" direction looks quite severe. Beyond that, it's difficult (for me at least) to be any more definitive just by looking at some low resolution images and not having the thing in my mitts to go further. I suppose that it's possible that some kind of light leak might give a similar problem although unlikely with this type of construction.

Sorry that I can't help further.

Bob
Click to expand...


Thanks Bob for all your help.

Spoke to my local camera engineer yesterday and he confirms that your diagnosis is almost certainly correct. He will strip the lens, correct the fault, give it a service and recalibrate it for me for £50. So not too bad.

Kind regards
 
£50 sounds like very good value when compared to the mainstream "fixers", Martin. Can I ask that you update this thread when it's sorted and the exact details are available....it all adds to the knowledge base.

Cheers
Bob
 
combat squirrel said:
Lenses at F1.4 'misfocusing' is due to as said, the tiny DOF and technique of the photographer, even with a 'perfect working lens' you will get many 'failed' shots because if u breath in or out after focusing that can affect it - extreme DOF is tricky.
Click to expand...

Whilst I agree with your comments on this occasion it is nothing to do with DOF it is a faulty lens pure and simple. If you look at the photos of the batteries or the tubs you will see that all are badly effected. If it was purely due to me moving slightly then one or the other batteries/tubs would still be properly focused but not necessarily the one I wanted. The fact that nothing in these photos is in focus shows there is an lens fault.

Canon Bob said:
£50 sounds like very good value when compared to the mainstream "fixers", Martin. Can I ask that you update this thread when it's sorted and the exact details are available....it all adds to the knowledge base.

Cheers
Bob
Click to expand...

Will do - I expect the repair to take about 7-10 days.
 
Just to bring people up to speed. I sold the lens to a member of the local camera club. He was not concerned about problems at f1.4 to f2.8 as he never shoots in those ranges?? I got a fair price and for his needs he got a cheap lens (saved me the cost of repair as well). So we were both happy.

If he ever does get it fixed I will post details of what was needed but don't hold your breath - I think there will be a long wait.:)
 
You must log in or register to reply here.
Back
Top