Is lens micro-adjustment all it's cracked up to be?

[onefivenine]

The other day I set up my 50mm lens at +10 microadjustment, using a page of text taped to the wall about 12 feet away. Camera on tripod. It was spot on.

Then tonight when trying some hand-held close distance wide open shots of some lilies I found it was a bit off, so re-adjusted and found the ideal was -10.

I dunno what anyone's elses thoughts are but it's a bit disappointing if it isn't constant depending on the subject distance.

Maybe I'm not using the right technique to calibrate it - is there an optimium calibration distance for different lenses? And if that's the case what do you do with a zoom?

What are other peoples experience with it?

[RobDickinson]

Friend with a D300 (and micro adjustment) has a similar issue in one lens is front focusing at short focal lengths and back focusing at the longer end.

I guess its better than nothing?

[onefivenine]

Sounds similar Rob.

Well maybe better than nothing but I'm not sure what to do! Maybe just forget about it and leave it in the middle?! Or familiarise myself with when to flip it one way or the other... oh and remember to do so at the right time.

[D-an-W]

Dave, I don't know if you have seen the website with some fancy images for setting up micro-adjustment?

I am in the canteen at work currently (Aren't iPhones just cool!) so don't have the link handy but if you need it I will post it when I get home.

[onefivenine]

No I haven't seen that. Any guides woiuld be appreciated!

[Jas H]

It's a lens design/quality issue, not a camera issue that the lens focal point varies over distance.

[onefivenine]

Originally Posted by Jas H

It's a lens design/quality issue, not a camera issue that the lens focal point varies over distance.

Understand that - just wondering how folks are working around it?

[puddleduck]

IMHO this is just a marketing feature and not useful.

For this to be useful you need to plot a focal length / subject distance curve - you can't do this with one value applied at all focal lenghts and distances.

For primes, it makes a bit more sense. Not for zooms though as they are rarely par-focal.

[D-an-W]

AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2

Was the place I meant for you to look at...

[onefivenine]

Originally Posted by puddleduck

IMHO this is just a marketing feature and not useful.

For this to be useful you need to plot a focal length / subject distance curve - you can't do this with one value applied at all focal lenghts and distances.

For primes, it makes a bit more sense. Not for zooms though as they are rarely par-focal.

That's interesting, if it's dependant on the lens being parfocal - perhaps it is worth doing on the 24-70L and 70-200 2.8 IS.

Originally Posted by D-an-W

AF microadjustment for the 1Ds mark III, 1D Mk3, 5D Mk2

Was the place I meant for you to look at...

Thanks mate - I'll have a good read of that site.

Cheers guys

[onefivenine]

Thanks again D-an-W

I used the downloadable test image and 'live view' focus method, and at the recommended distance of 2.5m I also got +10 with the 50mm f/1.4

I then moved the tripod to about 60cm from the screen and got the same.

I guess my handheld test wasn't up to it and I was concerned over nothing, besides at close distance I'd probably be focusing manually.

Cheers!

[RobDickinson]

Originally Posted by puddleduck

Not for zooms though as they are rarely par-focal.

SLR zooms are pretty much all parfocal though arnt they?

[onefivenine]

Originally Posted by RobDickinson

SLR zooms are pretty much all parfocal though arnt they?

Can only speak for Canon...

Parfocal zooms in the Canon EF lens line-up are essentially limited to the fixed-aperture L-series category and front-focusing zoom lenses.
The current products include:

* EF 16-35mm f/2.8L USM
* EF 17-40mm f/4L USM
* EF 24-70mm f/2.8L USM
* EF 70-200mm f/2.8L USM
* EF 70-200mm f/2.8L IS USM
* EF 70-200mm f/4L USM
* EF 75-300mm f/4-5.6 IS USM
* EF 75-300mm f/4-5.6 III USM
* EF 75-300mm f/4-5.6 III
* EF 90-300mm f/4.5-5.6 USM
* EF 90-300mm f/4.5-5.6

[puddleduck]

Originally Posted by RobDickinson

SLR zooms are pretty much all parfocal though arnt they?

No, not at all.

In fact I can't think of many (Nikon) lenses that do not require refocusing when say.. focusing at 70mm then zooming back to 24mm.

And therein - in a nutshell - is the problem with micro adjust where zooms are concerned.