Canon 85 1.8 front focussing

[Craigus]

Just picked up one of these from LCE, has anyone else had similar problems with this lens front focussing? Specifically at the widest apertures as it's most apparent there, I've dialled in some correction in camera which has helped but haven't been able to test fully yet, just curious if it is common with this lens?

 

[TimHughes]

I only have one of these and no experienced this problem, also don’t recall it raised in forums before ....

 

[Brazo]

It’s purely an issue between your camera and your lens. The same lens on a different camera will perform differently.

It is very frustrating though my (Nikon 85 1.8) went on a 300 shot real world test shoot today and very few found critical focus however every shot was in focus somewhere in the image! That somewhere was behind the point of focus as I have checked every single point of focus against each image on my screen.

For images taken far away the focus ended up being further back focus, close up shots ended up being less back focus.

That was at -8 adjustment value.

I’ll dial in more negative adjustments tomorrow and retest but I’m this far away from swapping to the Tamron lenses with the tap in console.

 

[Craigus]

So are you saying another copy may perform better? I've currently got it set to +15 in the micro adjustment which works indoors, I'm concerned it will throw it our over longer distances though but can't test that today...

 

[Brazo]

So are you saying another copy may perform better? I've currently got it set to +15 in the micro adjustment which works indoors, I'm concerned it will throw it our over longer distances though but can't test that today...

A camera has a certain af tolerance as does a lens.

In simple terms if a camera has a very slight tendency to back focus a perfect lens will need a small negative value (e.g -5) to focus correctly on that camera.

Should a not so perfect lens, say a slightly front focusing lens (e.g +5) be used on that camera both defects would be cancelled out and you would be fooled into thinking your camera and lens are ‘perfect’.

Either way don’t worry they are all within ‘tolerance’.

As to your question yes another copy could perform better or worse!

Test at the distance you like to shoot at most. If after extensive testing you can’t get results you like buy a modern Tamron or sigma lens and the required console/dock so the lens can be very accurately af adjusted at different distances. Whilst oem lenses can be fractionally sharper than quality 3rd party lenses, it’s somewhat a moot point if the oem lens can’t critically focus.

 

[GeeJay57]

Not had that issue with mine, either on my (now broken) 50D or 7DII (replacement for 50D).

 

[Brazo]

Well I set up a test chart and mounted my D600 and 85 1.8 on a tripod. I carefully manually focused a magnified live view image to get the best possible focus and then set about comparing it to the phase detection af values.

I’ll cut a long story short. An af adjust value of -18 matched my manually focused attempt and proved itself tack sharp on subsequent test shots in the garden. So I’m now happy with my lens! Just wished I did this before yesterday as having 300 back focused shots of your child on a day out is annoying!

 

[mjkent]

Just picked up one of these from LCE, has anyone else had similar problems with this lens front focussing? Specifically at the widest apertures as it's most apparent there, I've dialled in some correction in camera which has helped but haven't been able to test fully yet, just curious if it is common with this lens?

Hi,

Have similar problems with mine. Found recently that if I'm close to the subject then the focus is great. But if I'm far away then it always seems to front focus. Almost as if I have used the lower focus point and not the centre.