Autofocus micro-adjust

[Tricky]

Got home too late to really have a play with my new 7D, so decided to spend an hour (it soon became 2 hours) micro-adjusting the AF on my lenses. My old 40D didn't have this facility and I had long suspected that at least one was a little bit out.

I used the information and test charts provided here and here. My calibration findings were as follows:

[ATABLE]24-105| -5
Siggy 30mm | -8
60mm macro | -3
10-22 | -4
10-17 Fishy | -4
70-200 | -2
700-200 + 1.4x |-4[/ATABLE]
[not quite sure how you use the table facility on AP!]
Mod edit: fixed table ... use | as the column separator http://www.ausphotography.net.au/for...ad.php?t=39799

I think this probably tells me that my 7D has a small tendency towards 'minus'! Perhaps -4 is the camera, whilst the difference is each lens. These aren't big differences, well within manufacturing tolerances, and indeed illustrate the 'raison d'etre' for the micro-adjust facility.

I also noticed that on zoom lenses, the ideal calibration adjustment varied depending on the focal length. On the 70-200, the adjustment was -2 at both ends (70mm and 200mm), but 0 at around 135mm.

With the 24-105, the adjustment was around -5 from 35mm to 90mm, but then -6 at 105mm and 0 at 24mm! I suspect the depth of field at 24mm is fairly deep, so less critical... I left it at -5 as a compromise.

Anyway, I'll double-check the findings on 'real' subjects when I actually get a chance to go out and take some pictures!

[Paul G]

Do all lenses need to be adjusted like this or is it a Canon thing?

[Tricky]

I believe there's quite a few recent cameras that now have microadjust, across all of Canon, Nikon and Pentax (possibly others?). For Canon, I think the models who have it are 50D, 7D, 5D2, 1D3 and 1DS3.

If your camera's got microadjust, then I can't see why you wouldn't try using it. I've heard it said that upgrading from 40D to 50D is worth it for the microadjust alone. That said, we're talking pretty minor differences here: not sure I'd even notice a +/- 5 adjustment, maybe just marginally? I guess its just nice to know the lens focus is absolutely spot on...

[I @ M]

All camera / lens combinations without regard to manufacturer may need adjustment Paul. The micro adjust feature being adopted by manufacturers is a very worthwhile tool to be able to "fine tune" normal manufacturing tolerances as Tricky has discovered.

[balwoges]

What are the steps to micro-adjusting your camera, have just bought a 50D and would be interested to know.

[Steve Axford]

It's something that needs some care as the focus can vary depending in distance. So if you focus at the minimum distance that may be different from infinity! Just jumping in and doing something can make things worse, not better.

[Tricky]

It's something that needs some care as the focus can vary depending in distance. So if you focus at the minimum distance that may be different from infinity! Just jumping in and doing something can make things worse, not better.

That's very true. I tried the AF settings at various different distances and did note some small variations. Canon recommends a minimum focus distance of 50 times the focal length, ie 50mm x 50 = 2500mm = 2.5m metres. So that's 10 metres for a 200mm lens! I only got up to about 5 metres max distance last night, so I'm keen to double-check my calibration settings at nearer infinity when I get a chance to shoot outdoors.

[Tricky]

What are the steps to micro-adjusting your camera, have just bought a 50D and would be interested to know.

There's a couple of links in my original post which give information on how best to undertake the microadjust process.

Assuming you've got live view, then in summary the process is:

1. Find a high contrast image that your camera can easily lock onto. I used the image provided by northlight in the link above, as the moire patterns make it very obvious when you've got perfect focus (using live view to focus on a computer LCD introduces moire patterns when critical focus is achieved).

2. Set up your camera on a tripod, perfectly square to the image, at approx 50 times the focal length of the lens you're calibrating. Use a wide open aperture for your lens, as this gives the most narrow DOF. Have your camera set to spot focus.

3. Switch to live view and use the autofocus button to achieve focus using live view's contrast-based method. This is the most accurate method of achieving focus, but does take several seconds for the camera to work out. You'll know its working because the moire patterns are highly pronounced.

4. Then switch off live view. Closely watch the focus distance scale readout on your lens then press the autofocus button again. If the focus ring moves a tiny jot, then your autofocus is slightly out (you'll see the moire patterns have reduced slightly, if you switch back to live view). If focus is acquired with no movement of the focus ring, then your autofocus is spot on.

5. If your focus is out, then dial in a little calibration using the microadjust feature. I went 2 steps at a time, as 1 step is barely noticeable.

6. Repeat steps 3 to 5 above until your lens is perfectly spot on. Try the process at different distances, ie nearer and closer to the test image. If you're calibrating a zoom lens, then repeat the process at different focal lengths too, as there may be differences within the zoom lens' range, requiring a 'compromise' adjustment setting to be used. Canon recommend tunning a zoom lens at the maxmimum focal length of the lens - presumably as focus is more critical at longer focal lengths?

7. Repeat steps 3 to 6 for all your individual lenses. Your camera should recognise each lens separately and store the details of any adjustment so that it is automatically applied when you connect the lens.

Lastly, I think its worth testing out your new settings in the 'real world', ie not using test images and at different distances. I want to check my settings asap, particularly the zoom lenses at near infinity distances and the macro lens at 1:1 minimum focusing distance. You should be able to switch between adjusted and not-adjusted quite easily from the camera's menu, allowing you to test out whether there has really been an improvement.

[Riverlander]

I did the micro-adjustment on my 50D with the 100-400 lens and could not believe the result - it was -18. The adjustment made a hell of a difference to my bird photos.
I sent the lens to Canon, Sydney, who cleaned it and focused it for less than $200 including return freight, and it came back absolutely spot on. I thought the exercise was very worthshile.

[jev]

Chuck Westfall, spokesman of Canon USA, explains the procedure here. If you want to make things as easy as possible, use a Siemens star to focus on. Google "Siemens Star" and print one - just don't use a laser printer on normal office paper (works very bad).

it was -18.

That is very, very much. I've most of my lenses calibrated on the 5DII and none is off more than 4 points.

[dbax]

very interesting read people, thanks for posting this Tricky and thanks for all who responded and offered feed back.
Now that I've commented I'll be able to find this again and look at my camera in the daylight

[Tricky]

Chuck Westfall, spokesman of Canon USA, explains the procedure here. If you want to make things as easy as possible, use a Siemens star to focus on. Google "Siemens Star" and print one - just don't use a laser printer on normal office paper (works very bad).

That is certainly another way to do it... However, I would suggest that this is a MUCH more laborious way to do it than using the procedure I followed! The live view process can also be done anywhere - whilst using a pattern to induce moire is a very convenient way to check that adjustments have indeed resulted in perfect focus, the process can be followed "in the field" by locking onto any high contrast subject using live view and then checking whether the AF system also focuses at exactly the same point (ie focus ring doesn't move).

very interesting read people, thanks for posting this Tricky and thanks for all who responded and offered feed back.
Now that I've commented I'll be able to find this again and look at my camera in the daylight

No worries I think micro adjust would actually be an interesting thing to cover with a demonstration at AP meet-ups. Equally, if anyone in Brissy is struggling with micro adjust and wants a demo, just drop me a PM

I want to check my settings asap, particularly the zoom lenses at near infinity distances and the macro lens at 1:1 minimum focusing distance.

Hardly got any chance to take pictures today... left work early and headed to Mt Cootha, but caught in various thunderstorms. Only managed one picture, which I'll post somewhere. Anyway, whilst I was waiting undercover for the rain to pass, I checked the micro adjust on a couple of lenses at infinity, but focusing on random high contrast subjects in the distance. Both lenses came in perfect, no further adjustment needed beyond that set last night using the moire pattern.

However, I struggled a bit with the 60mm macro. The DOF is so wafer thin at minimum focus distance that it's almost impossible to set an adjustment that consistently gives zero movement between live view and AF focus. At infinty, the 60mm has around -2 adjustment, but even at zero adjustment, there isn't much movement (if any). So I left it at zero adjustment for the moment. The 60mm has consistently been one of the sharpest lenses I've got, and I tend to focus it manually most of the time in any case, so not much point fiddling with it!!

[enduro]

No it's not a Canon thing.

All camera / lens combinations without regard to manufacturer may need adjustment Paul. The micro adjust feature being adopted by manufacturers is a very worthwhile tool to be able to "fine tune" normal manufacturing tolerances as Tricky has discovered.

Agreed, this is called standard deviation and is a common statistic amongst all products from resistors right through to individual elements in your lens. Also from eggs through to whatever.

Do you recall the phrase "sharp copy" when used in terms where a lens is sold second hand? A not-so-sharp copy may prove much sharper when adj appropriately with a micro-adjust or calibration.

[Paul G]

I've done some digging around and found a lot of references to the newer Canon bodies that have this feature. One reference to Nikon's D3 & D300 and little else. One reference talked about DC Settings for the D200 (never heard of them) so there doesn't seem to be a lot of cameras around that have this useful function.I saw a couple of cropped examples of the difference microadjustment can make and it's noticeable straight out of the camera.

I take it that it is seperate to having lenses aligned or tuned by Canon or Nikon et al?

[jev]

There are many more that offer AF adjustment, see http://www.whibalhost.com/forum/showthread.php?t=8888 . Didn't check that list, but I trust it's quite accurate.

[TEITZY]

I think it's useful for confirming if you have a bad copy of a lens (front or back focusing) but it only creates more problems (at least in your head) when you start micro-adjusting every lens you own (as Steve pointed out above). Honestly I doubt in real-life stuations whether you would see any difference with a +5 or -5 setting if you have 'normal' within spec copy of a lens.

Personally I haven't needed to adjust any of my lenses (Nikon, Tamron, Sigma).

Cheers
Leigh

[Tricky]

I think it's useful for confirming if you have a bad copy of a lens (front or back focusing) but it only creates more problems (at least in your head) when you start micro-adjusting every lens you own (as Steve pointed out above). Honestly I doubt in real-life stuations whether you would see any difference with a +5 or -5 setting if you have 'normal' within spec copy of a lens.

Personally I haven't needed to adjust any of my lenses (Nikon, Tamron, Sigma).

Cheers
Leigh

Hi Leigh, we might have to agree to disagree on this For me, at least, there's a benefit in knowing for sure that my lenses are spot on. And it hardly creates more problems - you can disable the adjusted settings (ie back to zero adjustment on a single lens or all lenses) at the flick of a button...

Once you know how to do it, the micro-adjust process is pretty quick and easy. I reckon I could adjust a set of 5 lenses now in 30-40min. I suspect you're right that +/-5 is probably around the point where you'd notice a difference (depending on lens, focal distance etc); I thought my Siggy 30mm 1.4 wasn't quite right (but equally was prepared to put it down to photographer inadequacy / struggling with DOF at f/1.4!) but the adjustment of -8 was certainly visible and confirmed my suspicions.

[ricktas]

I have adjusted a couple of my lenses for the D3..isn't hard to do, and it cleverly stores the adjusted settings in a memory bank. As soon as the camera recognises the lens attached it adjusts focus based on the settings. I guess the 7D does the same.

Very handy feature. Worth noting to that lens focus can be affected by temperature (one reason Canon makes white lenses). A brisk cold day or very hot day can affect a lens (expansion and contraction). So if pinpoint focus sharpness is important it is worth also considering checking them under similar conditions to those that the lens is going to be used under

[enduro]

I have adjusted a couple of my lenses for the D3..isn't hard to do, and it cleverly stores the adjusted settings in a memory bank. As soon as the camera recognises the lens attached it adjusts focus based on the settings. I guess the 7D does the same.

Very handy feature. Worth noting to that lens focus can be affected by temperature (one reason Canon makes white lenses). A brisk cold day or very hot day can affect a lens (expansion and contraction). So if pinpoint focus sharpness is important it is worth also considering checking them under similar conditions to those that the lens is going to be used under

Agreed. The 7D manual asks [from memory] that is is better to do the adj in the field which we could conclude is their way of explaining for temp changes.

I had to add about 5points to my 400mm to get it pin sharp on an aperture of f/5.6 at a range of 10m. I'll be checking it again as the temp warms up. Ideally I'd suggest checking your lenses out in the field on an average temp day, say 25'C as a standard.

[B D H]

Got home too late to really have a play with my new 7D, so decided to spend an hour (it soon became 2 hours) micro-adjusting the AF on my lenses. My old 40D didn't have this facility and I had long suspected that at least one was a little bit out.

I used the information and test charts provided here and here. My calibration findings were as follows:

[ATABLE]24-105| -5
Siggy 30mm | -8
60mm macro | -3
10-22 | -4
10-17 Fishy | -4
70-200 | -2
700-200 + 1.4x |-4[/ATABLE]
[not quite sure how you use the table facility on AP!]
Mod edit: fixed table ... use | as the column separator http://www.ausphotography.net.au/for...ad.php?t=39799

I think this probably tells me that my 7D has a small tendency towards 'minus'! Perhaps -4 is the camera, whilst the difference is each lens. These aren't big differences, well within manufacturing tolerances, and indeed illustrate the 'raison d'etre' for the micro-adjust facility.

I also noticed that on zoom lenses, the ideal calibration adjustment varied depending on the focal length. On the 70-200, the adjustment was -2 at both ends (70mm and 200mm), but 0 at around 135mm.

With the 24-105, the adjustment was around -5 from 35mm to 90mm, but then -6 at 105mm and 0 at 24mm! I suspect the depth of field at 24mm is fairly deep, so less critical... I left it at -5 as a compromise.

Anyway, I'll double-check the findings on 'real' subjects when I actually get a chance to go out and take some pictures!

Hi
Does this feature allow indivduals settings per lens ? i.e. is there a micro focus preset memory
the reason I ask is, with my 40 D & 100-400L IS, like Riverlander has said I've long suspected things are not quite right

I took it to Canon at Nth Ryde & they told me they could adjust it (40D) but it could mean that other lenses I use may be then less than perfect, that & the 2 week+ turnaround turned me off the idea but now I'm not so sure - could be time for a 7D

Cheers