October 20, 2014, 11:41:51 PM

Author Topic: FoCal – Long / Fast Lens Calibration  (Read 3010 times)

mackguyver

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FoCal – Long / Fast Lens Calibration
« on: February 24, 2014, 10:08:52 AM »
I've noticed a fair number of posts on using FoCal, so I thought I'd share my technique.   I’ve been using FoCal since it was in beta and over the course of time, through lots of trial & error, I’ve figured out how to reliably calibrate long lenses and fast lenses.  Here’s how I do it:

Use Manual Mode: The automated mode has never given me reliable results, at least with fast or long lenses.  It takes longer, seems to take an inordinate number of extra shots, is not repeatable, and does not result in very good results.  For lenses slower than f/2.8, it works really well, though, if your camera supports it.
Do Not Use Back Button AF: As Neuroanatomist helped me discover, Back Button AF does not (reliably or at all) record the AFMA value in the EXIF metadata.

Target Preparation
1.   Use the PDF file and print it on matte heavyweight paper at the highest quality settings your printer allows
2.   For best results, mount the target on stiff cardboard – I use the protector sheet of cardboard that comes with the paper and use 3M 6090 photo mounting spray to glue them together

Calibration Target Set Up
1.   Use your most stable tripod/head combination, legs not extended, and set up roughly 20x to 30x focal length (i.e. 8-12 meters for a 400mm lens) from where you plan to mount the target.  I have found that this is the sweet spot – it keeps the target big enough to obtain excellent results and is close enough to average shooting distance and infinity to be accurate in the field.  I’ve also found that f/1.2 lenses work best around 20x.
2.   Add weight to the tripod – I use a 20lb sandbag
3.   Line up the front of your lens to it is as close to parallel to the target as possible.  If available, use your camera’s level feature to get the camera perfectly level.  A bubble level will do if your camera doesn’t have this feature. 
4.   Mount the target so it lines up with the center of the target matching the center of the viewfinder.  A second person is helpful but not necessary.  This usually takes a few tries.
5.   Make any minute adjustments (while keeping the camera perfectly level) to get the center point perfectly aligned with the center of the target.
6.   Lock the tripod head down tightly
7.   Light the target – the brighter the better.  I use 2 x Paul C. Buff Einstein lights (with 8” high output reflectors) with the modelling light turned on Full power.  The lights should be angled at roughly 30-45 degrees off axis from the target and the target should be lit as evenly as possible.

Camera Set Up
1.   Use the viewfinder cover to block light from entering the viewfinder
2.   Set camera to:
•   Aperture Priority Mode
•   Wide open aperture
•   ISO 100
•   Auto White Balance
•   RAW
•   +1 EV
•   Spot metering
•   Timer/remote mode
•   Set shutter control to activate AF & AE (this may be disabled if you usually use back-button AF)
•   Center point AF
•   Mirror-lock up enabled
•   Disable IS on the lens
•   Also, if you have a newer model, make sure AF is enabled for your focus-by-wire lenses like the 85 f/1.2 II

Calibration
1.   Record the current Auto-focus Microadjustment value (AFMA) for the lens
2.   Set the AFMA to -20
3.   Defocus the lens (towards infinity or minimum focus distance [MFD]) – it doesn’t matter which you use, but I’ve found that using a consistent direction helps
4.   Using a cable release or better yet, a wireless remote (like the RC-1 or RC-6), set to 2 or 10 second delay, press the remote shutter button to autofocus the lens and lock up the mirror.  After 2 or 10s, the shutter will trip
5.   Defocus and take a second shot (2 shots minimum should be used)
6.   Repeat steps 3-5 and take shots with the following series of AFMA values: -20, -15, -10, -5, 0, 5, 10, 15, 20

Analysis and Re-Calibration
1.   Remove the memory card, download the photos to your PC/Mac
2.   Launch FoCal, select Tools>Manual Mode
3.   Click on Add Files and select the shots you just took
4.   When they appear, make sure the AFMA values appear correctly (they should) and that you took all of the shots required
5.   Click on Select All
6.   Enable “Target Optimization”.  Unless you have the lens mounted on a copy stand or a SERIOUS tripod, the camera/lens will move very slightly as you adjust AFMA values - Target Optimization will adjust for that
7.   Click Analyze – wait for results
8.   After you obtain the results, go back and take AFMA shots around the predicted value – i.e. if FoCal says it’s +7, take additional shots at +4, +6, +7, +8, and +9
9.   Return to your PC, download these new files – re-run the analysis with the original files + the new ones.
10.   The results will now be as accurate as possible.
11.   Save the Report – good to have for later reference
12.   Return to camera, set AFMA to FoCal recommended value

Optional Steps
1.   Measure target size (in mm) of the strip at the top of the target – input into preferences
2.   Determine the white balance of your lights (Einstein modelling lights are 5200K) and input that into the white balance setting

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FoCal – Long / Fast Lens Calibration
« on: February 24, 2014, 10:08:52 AM »

ahab1372

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Re: FoCal – Long / Fast Lens Calibration
« Reply #1 on: February 24, 2014, 10:34:19 AM »
+1
although I prefer to take more additional shots in the first run instead of going through a second round

mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #2 on: February 24, 2014, 10:44:18 AM »
+1
although I prefer to take more additional shots in the first run instead of going through a second round
Thanks, and I often do that, too, especially if I've calibrated the lens before and know roughly where it will end up.  As FoCal has improved, however, I have found that shots beyond the 5 point spread are often unnecessary.  More often than not, I find that the extra shots result in the same calibration, especially for lenses f/2.8 or slower.  For my f/1.2 & 1.4 lenses, I have frequently taken shots at plus & minus 5 AFMA values to get the best results.  AFMA on these lenses not only makes the image sharper, it reduces CA.

neuroanatomist

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Re: FoCal – Long / Fast Lens Calibration
« Reply #3 on: February 24, 2014, 11:12:21 AM »
Thanks for posting!

+1
although I prefer to take more additional shots in the first run instead of going through a second round

Me, too.  Note that you can use back button AF, as long as you're holding the AF-ON button when you press the shutter to activate the timer.

Definitely get as much light as possible on the target.  Light levels in 11-12 EV range or higher give more consistent results.
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Re: FoCal – Long / Fast Lens Calibration
« Reply #4 on: February 24, 2014, 12:13:54 PM »
Great info. I've been pondering getting FoCal for my kit. I am also looking at the new Tamron 150-600. My question is whether I need the pro version if FoCal as that lens is greater than 400mm. I'm okay with doing all the stuff manually. Your thoughts?

Thanks!
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mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #5 on: February 24, 2014, 12:22:25 PM »
Great info. I've been pondering getting FoCal for my kit. I am also looking at the new Tamron 150-600. My question is whether I need the pro version if FoCal as that lens is greater than 400mm. I'm okay with doing all the stuff manually. Your thoughts?

Thanks!
Thanks and yes, for that lens you'll need the Pro version if you want to calibrate lenses over 400mm (the plus version works for lenses up to and including 400mm):
http://www.reikan.co.uk/focalweb/index.php/versions/version-comparison/

R1-7D

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Re: FoCal – Long / Fast Lens Calibration
« Reply #6 on: February 24, 2014, 12:28:00 PM »
This is great information. I too have noticed that FoCal doesn't work too well in auto/semiauto modes for fast lenses. I've never had the guts to try all manual, but I think I will give it a shot when the weather warms up here (don't have enough light or space in my house for adequate testing).


Thanks for all the effort you've put into this!
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Re: FoCal – Long / Fast Lens Calibration
« Reply #6 on: February 24, 2014, 12:28:00 PM »

mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #7 on: February 24, 2014, 12:43:07 PM »
This is great information. I too have noticed that FoCal doesn't work too well in auto/semiauto modes for fast lenses. I've never had the guts to try all manual, but I think I will give it a shot when the weather warms up here (don't have enough light or space in my house for adequate testing).


Thanks for all the effort you've put into this!
It sounds a lot harder than it actually is and once you try manual, you'll see that it's actually a lot faster because you can generally calibrate each lens in about 20-26 shots and while FoCal doesn't process instantly in Manual Mode, there's no more waiting for the USB cable transfers and slow RAW processing.  I calibrated my 300 f/2.8 IS II and both extenders on my 5DII and 5DIII bodies yesterday in about 20-25 minutes.  I came back and knocked out my new 50 f/1.2 on both bodies in about 10 minutes.  In full auto mode on my 5DII, it's usually 20+ minutes for a f/1.2 lens at which point it is giving "Poor" results and I usually stop it because it's racked up 30-40 shots or more.

Also, I often take shots for numerous lenses at once and then "Analyze" them on the PC in one sitting. The only trick is remembering to go back and put those lenses back on and set their AFMA values one-by-one.

One time I forgot and I was in the field shooting when I noticed all of my shots looked like crap and were horribly out of focus.  Must have bumped the diopter, right?  Nope, not that, hmmm, better check AFMA - oh, it's set to +20, oops!!!

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Re: FoCal – Long / Fast Lens Calibration
« Reply #8 on: February 24, 2014, 02:22:46 PM »
MackGuyver,

Thank you so much for taking the time to post your FoCal method. It's actually quite reassuring to me as I've had inconsistent results trying to calibrate my EF-S 17-55 F2.8 IS with my 70D (so much so, actually, that I've started to wonder if I have an issue with either the lens or the body). Granted, my lens is not nearly as fast as your F1.2, but it was nice to see that while results of the automated process were "poor" for your lens, you were much more successful via this manual method.

As soon as I come up with a better/brighter light source (maybe a couple of those 500W halogen work lights from my shop?), I'm going to follow your FoCal recipe to see how it goes. The 20lb sandbag is a great idea, too -- especially with my cheapo tripod.

I'm much more enthused to go give FoCal another try. Thanks again!


mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #9 on: February 24, 2014, 03:49:19 PM »
MackGuyver,

Thank you so much for taking the time to post your FoCal method. It's actually quite reassuring to me as I've had inconsistent results trying to calibrate my EF-S 17-55 F2.8 IS with my 70D (so much so, actually, that I've started to wonder if I have an issue with either the lens or the body). Granted, my lens is not nearly as fast as your F1.2, but it was nice to see that while results of the automated process were "poor" for your lens, you were much more successful via this manual method.

As soon as I come up with a better/brighter light source (maybe a couple of those 500W halogen work lights from my shop?), I'm going to follow your FoCal recipe to see how it goes. The 20lb sandbag is a great idea, too -- especially with my cheapo tripod.

I'm much more enthused to go give FoCal another try. Thanks again!
I'm happy to hear that you have enjoyed my post and you're very welcome.  I have also had issues calibrating f/2.8 lenses in full-auto mode - so I'm not surprised by the issues you've had with the 17-55 2.8 IS.  As Neuro said, adding more light is usually the best thing you can do (those shop lights should work well), followed by a stable tripod, and in my experience using Manual mode.  Getting a bit closer to the target really helps, too, as it gives FoCal more pixels to work with - around 25x should work well at f/2.8.  Initially I tried 50x (Canon's manual AFMA process recommendation) and found it didn't work well at all.  I moved closer and got great results. I was afraid they would affect the real-world autofocus, but that hasn't been the case, at least from 20x and further.

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Re: FoCal – Long / Fast Lens Calibration
« Reply #10 on: February 24, 2014, 08:36:54 PM »
Mackguyver,

I too would like to thank you for taking the time to post your FoCal method. I have used the LensAlign
MKII, but never getting consistent results...that's why I am seriously thinking about buying FoCal. 

I have a few questions, regarding calibrating zoom lenses. I have the 1DX and would be calibrating my
200-400mm 1.4X...I do know that you can calibrate at both ends of the zoom range, but would FoCal
recognize when I engage the internal 1.4x as well as the external 1.4x?

Thanks

mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #11 on: February 25, 2014, 12:17:14 AM »
Mackguyver,

I too would like to thank you for taking the time to post your FoCal method. I have used the LensAlign
MKII, but never getting consistent results...that's why I am seriously thinking about buying FoCal. 

I have a few questions, regarding calibrating zoom lenses. I have the 1DX and would be calibrating my
200-400mm 1.4X...I do know that you can calibrate at both ends of the zoom range, but would FoCal
recognize when I engage the internal 1.4x as well as the external 1.4x?

Thanks
Raptors, I am happy to pass along things I learn and yes, FoCal would recognize the lens via the EXIF data, and would give you the calibration for any focal length you choose.  I'm guessing the 1DX treats this as two lenses in the AFMA settings, right?  I see that DxO does that, so I'm betting that the camera sees a 200-400 1.4x and a 200-400 with 1.4 engaged or something like that and there are separate AFMA settings for each at W & T.  If that's correct, then FoCal would work the same way.

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Re: FoCal – Long / Fast Lens Calibration
« Reply #12 on: February 27, 2014, 07:29:48 AM »
Thanks for posting! I'm a relatively new FoCal user and I have been thrilled with the results!
Always happy to learn how the pros do it.
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Re: FoCal – Long / Fast Lens Calibration
« Reply #12 on: February 27, 2014, 07:29:48 AM »

Raptors

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Re: FoCal – Long / Fast Lens Calibration
« Reply #13 on: March 09, 2014, 07:34:27 PM »
Mackguyver,

I too would like to thank you for taking the time to post your FoCal method. I have used the LensAlign
MKII, but never getting consistent results...that's why I am seriously thinking about buying FoCal. 

I have a few questions, regarding calibrating zoom lenses. I have the 1DX and would be calibrating my
200-400mm 1.4X...I do know that you can calibrate at both ends of the zoom range, but would FoCal
recognize when I engage the internal 1.4x as well as the external 1.4x?

Thanks
Raptors, I am happy to pass along things I learn and yes, FoCal would recognize the lens via the EXIF data, and would give you the calibration for any focal length you choose.  I'm guessing the 1DX treats this as two lenses in the AFMA settings, right?  I see that DxO does that, so I'm betting that the camera sees a 200-400 1.4x and a 200-400 with 1.4 engaged or something like that and there are separate AFMA settings for each at W & T.  If that's correct, then FoCal would work the same way.

Mackguyver,

Thanks...sorry for the delay, I have been out of the city for a couple of weeks.  With the 1DX, the camera is able to save independent AFMA values for use w/ or w/o the built-in extender, as well as w/ or w/o the external 1.4x.  Here are the 4 different profiles from the camera.

1) AFMA, focal length 200-400mm
2) AFMA with the built-in extender, focal length 280-560mm
3) AMFA with the built-in 1.4x extender and the external 1.4x, focal length 292-784mm
4) AMFA with just the external 1.4x, focal length 280-560mm

For the target set up, you recommend roughly 20x to 30x focal length. What is the procedure for zoom lenses? As I can calibrate at both ends of the zoom range, I gather you need to change the distance to target for each focal length?

Sorry for all the questions...thanks in advance
Raptors

mackguyver

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Re: FoCal – Long / Fast Lens Calibration
« Reply #14 on: March 10, 2014, 09:27:36 AM »
Mackguyver,

I too would like to thank you for taking the time to post your FoCal method. I have used the LensAlign
MKII, but never getting consistent results...that's why I am seriously thinking about buying FoCal. 

I have a few questions, regarding calibrating zoom lenses. I have the 1DX and would be calibrating my
200-400mm 1.4X...I do know that you can calibrate at both ends of the zoom range, but would FoCal
recognize when I engage the internal 1.4x as well as the external 1.4x?

Thanks
Raptors, I am happy to pass along things I learn and yes, FoCal would recognize the lens via the EXIF data, and would give you the calibration for any focal length you choose.  I'm guessing the 1DX treats this as two lenses in the AFMA settings, right?  I see that DxO does that, so I'm betting that the camera sees a 200-400 1.4x and a 200-400 with 1.4 engaged or something like that and there are separate AFMA settings for each at W & T.  If that's correct, then FoCal would work the same way.

Mackguyver,

Thanks...sorry for the delay, I have been out of the city for a couple of weeks.  With the 1DX, the camera is able to save independent AFMA values for use w/ or w/o the built-in extender, as well as w/ or w/o the external 1.4x.  Here are the 4 different profiles from the camera.

1) AFMA, focal length 200-400mm
2) AFMA with the built-in extender, focal length 280-560mm
3) AMFA with the built-in 1.4x extender and the external 1.4x, focal length 292-784mm
4) AMFA with just the external 1.4x, focal length 280-560mm

For the target set up, you recommend roughly 20x to 30x focal length. What is the procedure for zoom lenses? As I can calibrate at both ends of the zoom range, I gather you need to change the distance to target for each focal length?

Sorry for all the questions...thanks in advance
Raptors
I guess I didn't cover zoom lenses or think about all of the combinations when you add in (external) extenders, but that makes sense in terms of the number of possible profiles for the 200-400 1.4x (with or without the internal 1.4x and external 1.4x).

To answer your question, yes, you need to move the camera for the Wide and Telephoto measurements, and a wise man will take photos with every camera body he owns before moving the set up.  Ask me how I know that ;).

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Re: FoCal – Long / Fast Lens Calibration
« Reply #14 on: March 10, 2014, 09:27:36 AM »