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Author Topic: Microadjustment  (Read 14649 times)

Mt Spokane Photography

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Re: Microadjustment
« Reply #30 on: September 28, 2011, 01:00:21 PM »
After reading and reading again all your posts, I spent a couple of days to setup a good microadjusting session. I opted for Jeffrey Friedl's method, that was well explained and didn't require to wait (and pay...) for a lensAlign to be shipped. The chart is well designed and the logic of the light grey indicators seems quite reasonable.
The lack of an instrumental system for a perfect alignment camera target required some additional time to spend leveling and measuring, but at last everything was perfectly aligned.
I started with the 1Ds3 and the 100-400, followed by the 5D2 and the same lens. At the beginning everything seemed working well, following well every step of the procedure. Frequently tested if the sensor was reading just the right target, turned off IS, fast shooting time, manually scanned from minimum distance to infinity before AF, camera on heavy tripod. Both cameras-lens seemed affected by a slight front-focusing corrected at -5 and -6.
Then, just for checking, I tried to set at -9 with the unlikely result to get again a front-focusing. Tried and tried again, getting similar results.
After reading an old article by Tom Jackson about the disalignment between the real sensor and the focus outlines in the viewfinder, I convinced my self that a lab procedure for microadjustment is risky and too exposed to minimal error factors.
So I reset everything and tomorrow I will go for what seems to me a more empirical and real world approach.
I will puth cameras and lenses on my tripod, aiming at the right distance for a wall plenty of contrasting and fine details. Then I will take 41 pictures focusing only with the central spot, adjusting from -20 to +20 and I will compare the results in LR3.4.
Quite rude but nor too time consuming, and it seems to me the exact procedure for what the MA system was  designed...
Any opinion?

I use Jeffreys chart as a starting point, and then verify with real world photos at various distances at full aperture.  Sometimes a little tweaking is needed, but its narrowed down any errors by quite a bit, usually to +/- 2.

I do plan to buy a lens alighn unit, but i never seem to get around to it, and all of my lenses produce very sharp images. 

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Re: Microadjustment
« Reply #30 on: September 28, 2011, 01:00:21 PM »

aldvan

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Re: Microadjustment
« Reply #31 on: September 28, 2011, 04:48:01 PM »
I received yesterday my LensAlign. Adding custom taxes and shipping the cost is unreasonable, per se, but the idea seems very good. I'm waiting for a relaxed moment of free time to MA my lenses...

aldvan

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Re: Microadjustment
« Reply #32 on: September 29, 2011, 01:40:57 PM »
Today I started the MAF campaign. I have some doubts and hope that neuroanatomist will solve them for me.
Aiming at the two holes for alignment, particularly with shorter than long tele lenses, as a 100 macro at the required distance of 25*focal lenght, it is impossible, due to parallax, to have both of the two holes perfectly centered. The rear ones are both perfectly visible trough the front ones, but slightly eccentrics. Is it ok anyway? I can't see any method to have both of them perfectly centered at short distance.
The 100 Macro IS seems ok with +4 and a real world test seems confirm that.
Second doubt. I found different answers in order to compensate MAF. To put it in a simpler way, if the perfectly focused point is behind the zero on the ruler (backfocus?) the adjustment should be + or -? I tried many times with controversial results... So, with LensAlign the 100-400 seems backfocusing, but with a backfocus adjustment of +14 (ok for the LA), the backfocusing gets worse in the real world...
Thanks in advance...

neuroanatomist

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Re: Microadjustment
« Reply #33 on: September 29, 2011, 02:11:05 PM »
Today I started the MAF campaign. I have some doubts and hope that neuroanatomist will solve them for me.

I'll do my best...   :)

Aiming at the two holes for alignment, particularly with shorter than long tele lenses, as a 100 macro at the required distance of 25*focal lenght, it is impossible, due to parallax, to have both of the two holes perfectly centered. The rear ones are both perfectly visible trough the front ones, but slightly eccentrics. Is it ok anyway? I can't see any method to have both of them perfectly centered at short distance.
The 100 Macro IS seems ok with +4 and a real world test seems confirm that.

I had to do a little digging, and it turns out that the LensAlign website claim that, "The graphics show the Pro model, however the MkII works exactly the same," is not quite true.  I assume you have the MkII version, as that's what is currently shipping.  I'd recommend aligning the hole on the left, i.e. the one in the center of the focus target, and let the other red circle be eccentric in the opening. 

The Pro model has 5 holes vs. two, one in the center and two on either side of that, and I usually try to ensure that the red bullseye in the middle is centered, and the ones to the side are displaced symmetrically (something you obviously cannot do with only one other hole).

Second doubt. I found different answers in order to compensate MAF. To put it in a simpler way, if the perfectly focused point is behind the zero on the ruler (backfocus?) the adjustment should be + or -? I tried many times with controversial results... So, with LensAlign the 100-400 seems backfocusing, but with a backfocus adjustment of +14 (ok for the LA), the backfocusing gets worse in the real world...

If your lens is backfocusing, i.e. the plane of sharp focus is behind the 0-point on the ruler, then you need to apply negative adjustment to correct it, i.e. -6 or -14, depending on how the severity of the backfocus.  An AFMA of +14 would make backfocus substantially worse.
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aldvan

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Re: Microadjustment
« Reply #34 on: September 29, 2011, 06:10:29 PM »
Thank you very much, neuroanatomist... After the first deluding attempts, I spent an hour to refine the procedure, and everything seems to go very well, now. Actually it needs a very longand accurate tune up, before starting, but after tha,t it is easier. The final result is  1Ds MkIII + 100-400 MAF +4, 5D MkII + 100-400 +2. Tomorrow I'll test this result in real world, and I'll tune up the other lenses...
During this kind of procedure you realize how flimsy are also good tripods. I have a Carbon Fiber and an heavy aluminum Manfrotto: I had to shoot with 10" timer to get a perfectly static image...

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Re: Microadjustment
« Reply #35 on: September 29, 2011, 07:10:04 PM »
Aiming at the two holes for alignment, particularly with shorter than long tele lenses, as a 100 macro at the required distance of 25*focal lenght, it is impossible, due to parallax, to have both of the two holes perfectly centered.
I noticed the same when doing my 100mm macro, on the back of the Lensalign Mk II the outer alignment hole is marked macro target so I used that one. I wasn't 100% sure though so tried the center one as well but results were too close to call, so it doesn't seem to make much difference. I'm guessing the outer one is just marked macro in case you're so close the center hole and ruler aren't visible at the same time.

aldvan

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Re: Microadjustment
« Reply #36 on: September 30, 2011, 01:27:42 AM »
Aiming at the two holes for alignment, particularly with shorter than long tele lenses, as a 100 macro at the required distance of 25*focal lenght, it is impossible, due to parallax, to have both of the two holes perfectly centered.
I noticed the same when doing my 100mm macro, on the back of the Lensalign Mk II the outer alignment hole is marked macro target so I used that one. I wasn't 100% sure though so tried the center one as well but results were too close to call, so it doesn't seem to make much difference. I'm guessing the outer one is just marked macro in case you're so close the center hole and ruler aren't visible at the same time.
I suspected that but I wasn't sure what he intended with 'macro target'...

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Re: Microadjustment
« Reply #36 on: September 30, 2011, 01:27:42 AM »

Viggo

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Re: Microadjustment
« Reply #37 on: September 30, 2011, 02:09:44 AM »
Neuroanatomist:

I took home with me a Spyder LensCal from work, and when using it, one actually doesn't need the distance I thought it would (comparing to the northernlight gif-image, pixel-allignment). And I adjusted 6 lenses on two bodies with half an hour, and they have all worked perfect since! Best tool you can buy ever.....

Thanks!
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neuroanatomist

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Re: Microadjustment
« Reply #38 on: September 30, 2011, 09:55:20 AM »
Glad to help!
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aldvan

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Re: Microadjustment
« Reply #39 on: October 01, 2011, 02:07:23 AM »
Final results: ISO 800, max opening, 10" timer, max focal lenght, central spot

1Ds MkIII
16-35 f/2.8 L II   0
24-105 f/4 L    +8
100 f/2.8 L Macro I   +4
100-400 f/4-5.6 L   +4

5D MkII
16-35 f/2.8 L II  +3
24-105 f/4 L   +2
100 f/2.8 L Macro I  +6
100-400 f/4-5.6 L  +2

It's evident that both the systems, withe very lens, are front focusing, and in a different way. So, I guess, the constant result should be charged mainly to the body instead to the lenses.
It's interesting to note that measurement was a pleasure with the 1Ds, showing a repeatable, constant and very precise progression from backfocusing to front focusing. The 5D was more unpredictable, showing a slightly random series of results, not always well connected between adjustment and focusing...

Mt Spokane Photography

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Re: Microadjustment
« Reply #40 on: October 04, 2011, 09:12:03 PM »
Lens align has some very simple online instructions, and even a distance calculator that you can use to calculate the distance.

Just go to the web site and click on how to use it.

http://michaeltapesdesign.com/lensalign.html

For example, a 100mm f/2.8 can be aligned at and distance between 8.2 and 16.4 ft and get good results. 

Mt Spokane Photography

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Re: Microadjustment
« Reply #41 on: October 10, 2011, 01:07:14 PM »
I finally bit the bullet and ordered a lens align MK II which I received a few days ago.  I managed to find three hours to play with it, reading the instructions online first and using the calculator to determine the minimum distance.  Then, I added about 10-20% so I was using it at about 30X the focal length, 25X for the long focal lengths.

I checked my setup by using the contrast detect focus in liveview.  It should result in a high percentage of perfect focus achieved.

What I quickly found is that the process is sensitive to even tiny misalignments and particularly to any tilting of the camera from side to side.  The front of the ruler almost always appeared to have more blur than the rear even when perfectly focused.  I believe that this comes from being too near the 25X focal length, but did not have time to confirm it.  I also found it necessary to turn off IS on my old 300mm f/4 lens to stop it from drifting.  The others did not drift, not even the 100-400mmL.

Most of my lenses were perfect with zero autofocus adjustment, or just needed one or two points, but two,my 24-105mm L and 85mm L needed a -10  tweaking due to backfocusing, even though the target fell within the depth of field and appeared sharp.  I did all the testing with my 5D MK II, using my 17mm prime, 24-105mmL, 35mm L, 50mm f/1.4, 85mm f/1.8, 100mm f/2.8L, 135mm f/2.8L, 70-200mm f/4 L IS, 100-400mm L, and 300mm f/4L.

I mounted the lens align on a old tripod I've had for 25 years which has a geared column that came in handy for raising and lowering the target to center it vertically.  I had to slide and rotate the tripod horizontally to get horizontal alignment, and that was difficult. 

Some things I'd like to have to make it easier:

External lighting on the target, my lighting was bright, but not adequate to do the testing at ISO 200.

A macro type rail turned sideways would have been a excellent time saver.  I have one out in my studio that I'll use next time.

A longer room.  I used a hallway which allowed mt to view the target at sufficent distance for the telephotos, but my large tripod wanted more room for the legs.

I did not create any before and after photos, but I saved the final ones along with a standard focused with contrast detect (I tried manually, but could not do any better).

I'll want to take some real world images, but its cold and raining this week.  We have had a cool and wet year so far in 2011.

Here is a example at 1:1 for my 35mmL and 100mmL comparing the image with contrast detect AF and the microadjusted phase detect.


100mmL with contrast detect AF


100mmL with phase detect AF (micro-adjusted)



35mmL with contrast detect AF



35mmLwith phase detect AF (micro-adjusted)


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Re: Microadjustment
« Reply #41 on: October 10, 2011, 01:07:14 PM »