AFMA – Easy or Not

[unfocused]

Okay, another thread had degenerated into like 10 pages of arguments over why Rebels need to have micro-adjust settings. (Actually "degenerated" is a relative term since the thread was pretty much at the bottom of the barrel to begin with, but that's another issue)

Anyway, at least one individual says doing a micro adjustment is easy and can be done on the fly while shooting, simply using any clearly delineated object (crack on a wall, blade of grass). That seems surprising to me, as I read numerous other threads here on the "best" system for adjusting lenses and most seem to require a pretty extensive set up with resolution charts, very bright lighting, rock-solid tripod, etc. etc. There is even a software program that has been promoted by many on this site as an aid to doing micro-adjustments.

Full disclosure here: I've never felt compelled to do any adjustment on my 7D. Maybe I'm just lucky with lenses. Maybe because I usually stop down. Maybe because I'm usually shooting with my 15-85, or my 70-300 L or 100-400 L and the depth of field compensates for any small differences in focusing plane. Maybe because the smaller sensor offers better apparent depth of field. Maybe because I've gotten pretty good at using Photoshop to increase apparent sharpness. Or maybe I'm just damn good.

So, which is it? Easy to do on the fly or four hours of my life I'll never get back setting up lights, tripod, camera, charts?

 

[iMagic]

My 2 cents.

I have found AFMA to be important for critically sharp auto focus. I cannot depend on the viewfinder to help much. Depending on your equipment, style, and output some people may not notice the difference. For me I do. For example, my 100L macro needs +8 and that is even after Canon calibrated it. My other large aperture lenses also need AFMA to get that sharp focus which is needed on say someones eye(s) in a portrait. I think in a lot of cases the result can be greatly improved with AFMA. If you manually focus/use zoomed live view, stop down, subject is far away, etc. it may not make a noticeable difference. The point being, if I know my equipment can do something and it is not doing it then why did I spend all that money? I want to produce results that the average person could not.

PS or other sharpening techniques can mask a slightly out of focus picture. But I would prefer not to oversharpen. It will soon look unnatural.

Getting the right AFMA value can be difficult. Using a crack or other sharp contrast item helps. I found that this is a good starting point to determine how bad/good the situation is. For complete confidence then FoCal is probably the best tool there is. It can confirm your initial findings and fine tune it further. Yes it takes money and time. But I found it worth that investment.

Anyways, to each their own so if you are happy then why sweat it? Unless your curiosity is piqued. In that case take your 7d and a lens. Triopd it with say a flat dollar bill on a wall with good light at 25 to 50 times the focal length of the lens. Let it autofocus. Then zoom in and take a look. Then use AFMA and +5 and -5 to see if it gets better or worse. Let us know what you find.

 

[Loswr]

Sure, it can be done easily. As you say, all you need is a high contrast object to focus on and take a couple of shots. Better yet, any former RPG junkies (aka D&D nerds ), you probably still have one of those 20-sided dice, so roll a d6 with 1-3 being negative and 4-6 being positive, and the AFMA value from the d20.

Of course, there's doing an AFMA, but then there's doing it correctly...

Seriously, there's a reason Canon sort of discourages doing it in the manual, warning that it may prevent you from achieving proper focus. AF systems are neither perfectly precise nor perfectly accurate - multiple shots are required, the target must be appropriate, flat where the AF point is (the whole real one, not smaller-than-real little box in the VF), etc. I really recommend using FoCal or a commercial tool like LensAlign or SpyderLensCal, and take lots of shots.

 

[Don Haines]

I'm sure that you can do it quick and easy..... but that's a far cry from quick and easy and accurate.

I decided once to try it on a 5D2 with the ruler on the floor and seing just where the focus point was. I tried it with three different lenses, making notes of where it focused. Then I re-did the test and got different numbers. Then I redid the test and got another set of numbers. They were all clustered around where focus should have been and the numbers were similar, so I left well enough alone.

The accuracy needed for AFMA was greater than my setup's accuracy. I could get "close" but not exact... and the realization that the lenses were already closr than the accuracy of my test is what made me stop. In other words, I would have done a quick and easy AFMA that made things worse.

 

[Dantana]

Child's-play! Now I really don't understand why Rebels don't have AMFA.

Whoops, sorry, left my sarcasm filter on. I'll have to watch that.

 

[TrumpetPower!]

Good. Fast. Cheap.

Pick two.

If you want good and fast (which also means easy), just get Reikan FoCal and be done with it. All you need is a solid tripod and floor (concrete pads such as for a driveway or sidewalk are awesome) and a lot of light (direct sun is also awesome). Then, just tape the target to the proverbial brick wall, point the camera square at the target at the indicated distance, click a few buttons, twiddle your thumbs for a minute or three, and all is done.

No other option is going to do better than FoCal, though some might perhaps equal it.

There's an interesting new idea floating around that's gotten the moniker "DotTune" that's free and relatively painless, but the jury is still out on how well it works...some have had success, others haven't. Might be worth trying if you're allergic to the thought of spending money.

On the other hand...FoCal doesn't even cost as much as a decent polarizer, and you just need to buy it once, so I don't know why anybody balks at buying it....

Cheers,

b&

 

[Mt Spokane Photography]

I've done a AFMA on the fly when I noticed that my camera-lens combination was not zeroed in for the very long range shots with a 35mm L lens that was the only lens I had with me. It had been adjusted for 10 ft, not 200 ft.

However, the adjustment was only valid for that particular distance. I then sent the lens to Canon because of the large adjustment required, and it came back with a "0" AFMA on all my bodies.

 

[LetTheRightLensIn]

Sure, it can be done easily. As you say, all you need is a high contrast object to focus on and take a couple of shots. Better yet, any former RPG junkies (aka D&D nerds ), you probably still have one of those 20-sided dice, so roll a d6 with 1-3 being negative and 4-6 being positive, and the AFMA value from the d20.

Of course, there's doing an AFMA, but then there's doing it correctly...

Seriously, there's a reason Canon sort of discourages doing it in the manual, warning that it may prevent you from achieving proper focus. AF systems are neither perfectly precise nor perfectly accurate - multiple shots are required, the target must be appropriate, flat where the AF point is (the whole real one, not smaller-than-real little box in the VF), etc. I really recommend using FoCal or a commercial tool like LensAlign or SpyderLensCal, and take lots of shots.

They also recommend doing in the field too .

Honestly aiming at a pavement crack gets you 99% of the way there and same goes for picking some player standing around and taking some shots and checking at 100% view. People do it one the sidelines. You can tune it to typical distance being shot at at the time. Once had a 5D2 and 50D and 300 2.8 and a TC, before doing some quick MFA on the field I was getting like 1 in 6 shots with good focus, a total mess, a quick tune and sudden;y using the TC was viable for the soccer match.

Another nice reason for MFA, what if you end up using pool equipment from a newspaper? You are not in control over when/if/how it gets calibrated. And if you grab a lens maybe you do need to do a quick MFA on the field of play. (And speaking of Rebels again, lots of students use them and many school papers have pool lenses so you can see Rebel users could surely make use of MFA.)

Don't aim it at some ruler 1' away from you that is way too close for one and gives it too many things to grab on for another.

 

[cccp80]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

 

[digital paradise]

Sure, it can be done easily. As you say, all you need is a high contrast object to focus on and take a couple of shots. Better yet, any former RPG junkies (aka D&D nerds ), you probably still have one of those 20-sided dice, so roll a d6 with 1-3 being negative and 4-6 being positive, and the AFMA value from the d20.

Of course, there's doing an AFMA, but then there's doing it correctly...

Seriously, there's a reason Canon sort of discourages doing it in the manual, warning that it may prevent you from achieving proper focus. AF systems are neither perfectly precise nor perfectly accurate - multiple shots are required, the target must be appropriate, flat where the AF point is (the whole real one, not smaller-than-real little box in the VF), etc. I really recommend using FoCal or a commercial tool like LensAlign or SpyderLensCal, and take lots of shots.

I am not a big supporter of AFMA. It is different now because back in the day before automated systems like FoCal and now DotTune it was a little to out of control for me. Too many methods out there. There was the old ruler and hold your camera at a 45 degree angle? I'm not putting air in my tires, I'm working with expensive, high precision equipment. I prefer to have trained technicians that have the proper equipment working on my gear. They do multiple measurements. So if I think something is off as much of pain as it is I send it to Canon.

Very seldom does anyone bring up the operator manual. I have many times and am usually ignored. I'm not sure how many times I have read about people asking questions about other issues and the reply is "read the manual". I jokingly think "but ignore the page and warning about AFMA " Just saying.

Also without an automated system I always second guessed myself even using Lens Align. I'd set it one day, go back the next and got different results. I tried my 100L Macro and got different results at 8, 12 and 16 feet which supports the manual. For best results adjust at location.

One more thing. It is known that phase detect AF can be affected by different light sources. Incandescent and fluorescent will yield different results. Something else to consider.

I know people swear by it and I can see it's value with 3rd party lenses but there are times I think Canon put it in so they can save money on warranty returns. There is variation in every manufacturing and there are tolerances. If your manufacturing process is a little off one week and outside the specs the customers can fix it using AMFA. I know about that. 30+ years in manufacturing and trust me, you don't want to know what goes on.

Currently all my Canon lenses have zero AMFA on both bodies and I can produce tack sharp images on all of them. I don't bother if they are out a few ticks one way. Next day, distance and light changes and it will be out the other way. I really like DotTune as it gives me a good idea on my lenses performance. If out consistently more that 3 to 4 ticks it goes to Canon.

I can been contemplating getting Focal just to see what it is about.

 

[digital paradise]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

Yes. Typically they say at the farthest focal point - 70-200 so you AFMA @ 200. Some people say to split the difference. I do that when I put air in my tires ;D.

 

[digital paradise]

I just wanted to add. All lens manufacturers were a little sloppy but you could get away with it with film. Digital changed everything. Also I doubt there is too much QC going after the manufacturing process. The Japanese manufacturing process considers it a waste. It is a bottle neck because you have to store it, move it around, it takes longer to get to market and people make mistakes when doing QC. They may sample a few but I doubt all are checked.

Where the Japanese excelled was QC during the manufacturing process which insures a defect free product at the end of the line. It is a lot of hard work, you really pay attention to everything which includes tolerances of supplied parts from other companies. It has been 8 years since the real dawn of digital which I consider to be the 20D and 5D.

So in that 8 years I think Canon has gotten better in the last several. There seems to be less talk about copy variation with the new 24-70II and others. Actually I read that Canon delayed the release to insure the it's manufacturing was dialled in properly. I can't back that. According to DotTune my new 24-70II is - 1 @24 and +1 @70.

 

[Loswr]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

I wouldn't say pointless. I had a zoom that on my 7D needed +3 at the wide end and +7 at the long end. Leaving it at zero wouldn't be optimal, obviously. Generally, the DoF will be shallower at the long end. In that case, +6 was the compromise value.

Having the two settings is nice, though. The most recent zoom I tested on my 1D X needs 0 at the wide end and +5 at the long end. But I can imagine that sometimes two settings wouldn't be enough. The camera does a simple linear regression with focal length between the W and T values. For that lens, the two intermediate focal lengths I tested had AFMA values that fall right on that line. If they hadn't, the lens would have gone back.

 

[digital paradise]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

I wouldn't say pointless. I had a zoom that on my 7D needed +3 at the wide end and +7 at the long end. Leaving it at zero wouldn't be optimal, obviously. Generally, the DoF will be shallower at the long end. In that case, +6 was the compromise value.

Having the two settings is nice, though. The most recent zoom I tested on my 1D X needs 0 at the wide end and +5 at the long end. But I can imagine that sometimes two settings wouldn't be enough. The camera does a simple linear regression with focal length between the W and T values. For that lens, the two intermediate focal lengths I tested had AFMA values that fall right on that line. If they hadn't, the lens would have gone back.

I was mostly kidding about the tires. I believe people get good results. I just don't trust myself.

 

[cccp80]

I wouldn't say pointless. I had a zoom that on my 7D needed +3 at the wide end and +7 at the long end. Leaving it at zero wouldn't be optimal, obviously. Generally, the DoF will be shallower at the long end. In that case, +6 was the compromise value.

Having the two settings is nice, though. The most recent zoom I tested on my 1D X needs 0 at the wide end and +5 at the long end. But I can imagine that sometimes two settings wouldn't be enough. The camera does a simple linear regression with focal length between the W and T values. For that lens, the two intermediate focal lengths I tested had AFMA values that fall right on that line. If they hadn't, the lens would have gone back.

Good point. I like your idea to put the correction closer to the long end. Thanks for the tip!

 

[LetTheRightLensIn]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

Not necessarily at all. So far for all of my L zooms and my tamron zooms it's been nearly the same value needed at either end, although for one canon non-L it was problematic with the older MFA system since the ends were very different, but I could at least fix one end on the spot to get by in the meantime.

 

[bycostello]

hard...

 

[digital paradise]

hard...

I guess I could have been less winded and just said that ;D

 

[Zen]

According to DotTune, my 24-70 2.8 II is spot on at 0!

I've checked all my lenses and all are quite acceptable. Don't understand why others have so much trouble!

Maybe my standards are lower??

Z

 

[Mt Spokane Photography]

Just want to add something that hasn't been discussed before: it is pointless to do microadjust zoom lenses (unless you have the latest models that actually allow to do that) - the amount of correction you will need for smallest/largest focal lengths will be different.

I have found only a small difference in AFMA between wide and zoom for most of my lenses. Picking a mid point, or for a lens like my 100-400mmL, the long end works fine. Its far better than having all focal lengths be off.

Here are some results of my tests for my zoom lenses.


Canon 24-105mm L

24mm +0

50mm -3

105mm -2

Canon 70-200mm f/4L IS

70mm -5

100mm -3

200mm -3