AF micro adjust!

babowc

Didn't use any fancy programs or gadgets, but got all of my lenses calibrated using a small tip of a light stand!

Wow, many of my lenses were SO off!
Especially the 24, 35, 50, and 85mm 1.4 primes! My 24 required -20 calibration

It made a night and day difference though! Every shot is focused exactly where I had the dot.

Now I see why this is so necessary!

P.s, the only one lens that did not require AF adjust was the 200 f4 micro! It focused perfectly with the D800!

ziggy53

As long as you gain consistency going forward, it sounds like you made considerable improvement.

babowc

I started AF adjusting on my second body, but it's completely different from the first.
Despite being the same model, each body and lens combination must be unique. And thus requiring different AF adjust.

ziggy53

As long as you see a "trend" and a similarity between the micro-focus adjustments (MFA), differences between bodies is perfectly normal.

For instance, if you rank your lenses from greatest positive MFA through greatest negative MFA on one body, you should see the same (or an extremely similar) ranking of the lenses on a second body.

Netgarden

I've only used micro adjustment on one lens, and I have 6 "L"s. My theory is if you have to microadjust almost all of your lenses then the camera is what needs to be calibrated. [easy for me to say because I live near a Canon service co.] But surely before 'microadjusting' came along what did people do? I feel that for the amount of money we spend on our gear, all of it should be spec to begin with. A "fixed" accuracy doesn't always mean best.

And also, realizing what length we use the most, for zoom lenses or telephoto long lenses, microfocusing at a close object won't fix the long end.

babowc

I "sort-of" realized that when I used my 85 1.4D in further distances.
It wasn't as accurate as the micro adjust made it out to be, especially near infinity.
Needless to say, I was a bit disappointed.

jmphotocraft

Welcome to 2008. ;-)

Matthew Saville

Netgarden wrote: »

I've only used micro adjustment on one lens, and I have 6 "L"s. My theory is if you have to microadjust almost all of your lenses then the camera is what needs to be calibrated. [easy for me to say because I live near a Canon service co.] But surely before 'microadjusting' came along what did people do? I feel that for the amount of money we spend on our gear, all of it should be spec to begin with. A "fixed" accuracy doesn't always mean best.

And also, realizing what length we use the most, for zoom lenses or telephoto long lenses, microfocusing at a close object won't fix the long end.

Here's my theory: AF Microadjust came out at around the same time as the whole shallow DOF craze, with portrait and wedding photographers shooting wide open at f/1.2 and f/1.4 90% of their workdays. Before then, most sane people stopped down a little bit, and/or just chalked it up to crappy autofocus in general. (Because, let's face it, even if the likes of the Canon 5D mk1 did have AF Microadjust, it wouldn't have magically given everybody 100% in-focus shots!)

Thus, this is simply another push of another envelope in another direction. Kinda like another question very similar to yours, that people often ask these days: "Before clean high ISO's came along, what did people do?"

This is just technology pushing the envelope, allowing us to more consistently create images that would have been previously unwise to attempt in a "clutch" situation. Now, for example, I don't hesitate to shoot a family formal in a dimly lit church at ISO 1600 or 3200. A family formal! Nor do I hesitate to shoot other portraits, or dance floors etc. in nearly pitch-black situations wide open at f/1.4...

=Matt=

pathfinder

Any lens that consistently required -20 to bring to focus on more than one body, I would send off to Canon Factory Service to have the lens checked, as I think that is out of tolerance.

My 300 f2.8 IS L was requiring -19 on one body, so I did send it off to Canon for evaluation, and they did end up replacing the focus module in the lens, so it can happen. Ow it works just fine again, even without MicroFocus adjustments.

babowc

Yeah, my 24 1.4 is pretty banged up, as it was one of the earlier lenses I purchased.
I haven't registered with Nikon, so I'll have to rummage the paperwork!

pemmett

Recommended AF Micro Adjustment techniques
Does anyone have a preferred method for AF Micro Adjustment for lenses? Thanks.

ziggy53

pemmett wrote: »

Does anyone have a preferred method for AF Micro Adjustment for lenses? Thanks.

Yes, I do. The first thing to mention is that you need to simplify the subject matter to a simple flat target, with enough texture to make AF dead simple, and enough size to eliminate AF distractions. As such, I no longer recommend using a "slanted ruler" or similar as the target, nor do I recommend using a high-contrast central target with a ruler off-center. Both of those can lead to erroneous results.

Instead, I highly recommend a brick wall, with the camera carefully aligned to the wall so that the focal plane is parallel to the wall. The wall should also be lighted so that the texture is easy to pick up for the AF module. Specifically:

1) Basic AF accuracy is best accomplished using a flat target, i.e. a brick wall or other large textured surface. If a camera/lens cannot accomplish this task, it has no chance of passing any subsequent AF tests including real world use. Make sure that the target is at the typical distance for your normal use of the lens, meaning that a long focal length lens that you would normally use for wildlife at a distance should be tested at that same distance for AF accuracy. Always test a lens at least twice Minimum-Focus-Distance (MFD). Lenses rarely do their best at MFD (the exception being true "macro" lenses.)

If a lens shows consistent front or back focusing with the wall test, then use micro-focus adjust technique until you get consistent accuracy. If the particular camera body does not have a micro-focus option, it should be serviced, or the lens should be serviced. If you have consistent results with all lenses then send in the camera. If the problem only exists with a particular lens, it's the lens that needs service.

If the camera does have micro-focus adjust, consider using software designed to simplify the process, like "FocusTune" by Michael Tapes Design, or Reikan "FoCal". Otherwise, start with rather coarse micro-focus increments and test images. Once you determine a correct range of best results, repeat the process with finer increments in the most successful range.

If the lens passes the wall test, proceed to the next test. If the lens fails the wall test and you cannot gain accurate AF with micro-adjust, send the lens back to where it came from or explore camera issues.

2) A fence line or similar, shot at an angle to the subject. Put a singular strong-contrast target on the top of the middle post and use a single focus point in the camera to focus against the target. This shows focus accuracy and/or how easily distracting for/aft objects influence AF accuracy (compared to the above wall shot). It also shows bokeh tendencies at different aperture settings.

3) A focus target/chart like in the following:

http://regex.info/blog/photo-tech/focus-chart

I do recommend testing these charts at twice minimum focus distance or greater. Most lenses, especially most zoom lenses, do not do their best at MFD. True macro lenses are the major exception.

4) A US stop sign, or similar very high contrast signage, both centered and off center and to the side and/or corner. This can show chromatic errors and off-axis errors.

5) Now just shoot "typical" subjects for your use of the lens(es). It's important that the lens perform correctly for your intended uses.

SteveF

Good advice.

While some seem hesitant to check this, it seems odd to me not to.

Of course they should be perfect out of the box, but this is life. Put in 15 minutes of time and your photos will consistently look better.