Micro Adjustments - different results for different focussing distances

[pmack]

I've finally got around to micro adjusting my 50mm f/1.4 on my 7D, which I had noticed was front focussing. I noticed this after photographing indoor theatre. I usually use the lens for close-up portraits , but for the theatre, i was 10-15 meters away from the stage.


I followed canon's advice, shot at 50 times focal length (2.5 meters), manually de-focused to infinity before each shot. I took three shots at 0, three at +5, then three at +10 etc...

After some testing with different values, the adjustment for +2 seemed the best.
It didn't seem much of a difference to the default zero, which surprised me because i was sure the lens was front focussing.

So i then went outside and tried this method on various flat objects (with good contrast) approximately 10 meters away. At the setting of +2, it was blurred.
After performing the same testing, i got reasonable results at +10, and slightly better results at +20!!!!


So I understand the setting only works for one focal length, and you should set it at the focal length you use the most, but is it too much to ask for a lens that can focus well regardless of distance, or is this acceptable behaviour?

I mean at least i now know if i want to shoot theatre again, change it to +15 to +20, and for closeups, take it back to +2, but that's hardly ideal when you are taking various shots at various distances.

Thanks

PS. for those wanting to critique my testing methods, please go away as no-one wants a repeat of last thread :th3:

[Lance B]

Sometimes the lighting can have an effect on how the AF works in the camera, so, if you're shooting in incandescent lighting inside and then go outside to normal sunshine, the AF will behave differently. This has to do with the fact that incandescent lighting has a more prominent yellow cast and therefore the yellow end of the spectrum causes a slight anomoly in the way the AF works.

[Max]

I have had a huge amount of problems with my 50mm 1.8 mkII.
I could never get sharp photos of the kids. Have tried various methods, ie using the lcd monitor, and charts that are either at 45 degrees or the camera is at 45 degrees with the chart flat. Anyway after getting it right on whatever method, its now on +18, I would then chase the kids around and it performs nicely, but only if I use it for close up stuff. Typically less than 1.5m, its really sharp especially at 2.8. But anything further away and its out again, it then back focues.

Would love to know why its doing that. If I stand at 30degrees to my fence and focus on one spot and then take a shot, then focus on a far away tree and take a step back, then focus on the same spot and take another shot. etc it easily repeatable and shows how it goes from spot on to back focusing as I go further away.

Its driving me mad and I was going to just buy the 50 1.4.
Is this a general 50 prime issue, my 100macro L isn`t doing that.

[pmack]

Interesting, sounds like yours is doing the opposite of mine, eg. if i set mine to work well for close ups, my long shots front focus, meaning i would have to take step forward. But if i set my adjustment for the long shots, then my close ups back focus.

Lance B, interesting, though i was using natural indoor lighting, and oudoor was overcast. I redid my testing again, both in simillar outdoor lighting and results were more or less the same.

[pmack]

has anybody else had simillar experiences?

[arthurking83]

has anybody else had simillar experiences?

Yep!

obviously not with any Canon products, but certainly with my (now gone) Nikon 80-200/2.8 and the Tammy 28-75/2.8.. all on the D300.
The Sigma 50/1.4 does seem to front focus a little at very close(ie. basically unusable) distances, but seems to focus spot on at normal working distances(say for people shots at the 1-3meter range).

Apparently this is more common than many would initially believe it to be, and judging by my experience, with my currently gear list, it must be related to lens(in isolation) or the dreaded camera to lens tolerances issue

Unless you want to send the camera and lens in for a service/calibration, I would set any micro adjust for a good balance of distances, where one may be compromised a little to achieve a better result at the other end of the distance scale.

[pmack]

Hmmm interesting. I'm wondering whether to send it to canon to see if they can calibrate the lens (is that even possible?), other option is to just sell it on ebay and buy a new one and hope for the best
(no doubt next lens will be the same or worse)

[Bennymiata]

Either that, or just focus manually!

[Ms Monny]

I read somewhere here very recently about certain lens' not seeming to be calibrated with the body. Here is the link to the other post in regards to this...

http://www.ausphotography.net.au/forum/showthread.php?80902-quot-This-Lens-is-Soft...-!-quot-READ-THIS-FIRST&highlight=calibration

I read it and it made perfect sense!!

[pmack]

Interesting article.
Sounds all to familliar to me, I've had problems at work with machiners not machining components with tolerances specified by me of +- 0.02mm (so 40 microns range) on a one inch diameter component...
I discovered the error when i was assembly a prototype, it didn't fit how i thought it would, and a measurement proved my hunch.
So a tolerance of 20 or so microns causing problems isn't as unusual as it sounds.

one thing that article doesn't touch on is the specifics of the issue that i'm having.
the article says that microadjustments fix the issue, whereas clearly they do not in my case.

[Speedway]

If I was having all the problems you seem to be having I would have sent the camera and offending lenses back long ago and let Canon sort it.
Keith.

[pmack]

yeah i'm the king of putting things off, and yet i drive past their service center every day...
will call them this following week, and will post back what happens