Looking for help calibrating Sigma 18-35 with dock.

I purchased my neighbor's 6 month old, barely used 18-35mm f/1.8 for $600 CDN. Seemed like too good of a deal to pass on. It's front focusing terribly on my 7D so I need to calibrate it. I've used the "Dot Tune" method in the past and am wondering if this will yield me the best results. Who has calibrated their 18-35 using the dock? Just hoping for advice. Be as detailed as possible. Thanks!

I'm no help with the dock, but I would calibrate it using the AFMA on the 7D first. If you use the dock, you have to keep mounting it on the camera and then the dock and so on until its right. If you see a situation where you are getting front focusing up close and back focusing on distant objects (or vice versa), then start using the dock to more or less program in a slope of the focus line based on subject distance to correct for that. Canon AFMA can only adjust the zero point and not the slope of the line so that is where the Sigma dock will help.

FEChariot wrote in post #17078073
I'm no help with the dock, but I would calibrate it using the AFMA on the 7D first. If you use the dock, you have to keep mounting it on the camera and then the dock and so on until its right. If you see a situation where you are getting front focusing up close and back focusing on distant objects (or vice versa), then start using the dock to more or less program in a slope of the focus line based on subject distance to correct for that. Canon AFMA can only adjust the zero point and not the slope of the line so that is where the Sigma dock will help.

Unfortunately this doesn't help me much the dock allows 16 MA variables.

i didn't have to calibrate my 120-300OS, but i could see it being a bit of a pain if you had to...i think fechariot's suggestion of seeing if it works with just the Micro focus adjust of your 7D could be a good one...and if the lens is consistently focusing incorrectly it may be all you need...if however the focusing is different for varying subject locations, you'll have no choice but to take the time to do it on the dock

I calibrated my 18-35 with the dock manually.

Basically I just set up the target at each distant shown in the calibration software. I'd Take a shot, switch to live view, zoom in on live view and manually focus the lens to get proper focus (to check for front or back focus). I'd do this several times to make sure it was infact front or back focusing.

After that I'd take the lens off the camera (that I had on my tripod), hook it to my computer, then just take an educated guess at how much adjustment was needed. If I had to correct focus by a lot then I made a larger adjustment then if I just had to tweak the focus a little. Disconnet the lens from the dock, Re-mount the lens, and start the process over again until the focus was right on.

Once the focus was right I'd move onto the next focal length for that distance. When I fixed each focal length at a certain distance I'd move onto the next of focus distance.

Not hard just time consuming. I tried a couple different ways first but the method above is what worked best for me. With that method it took me about an hour to go through all 16 adjustment values. A put the screen shot of my final adjustments in the 18-35 sample thread.......I would highly suggest saving a screen shot of the final adjustment screen just in case the lens reset the adjustment after a firmware update or anything.

Oh and nice deal you got on the lens too!

I rented this lens and it was front focusing really badly too.
Made a post about it in the lens archive.
I've never had a problem with 10-20, 30, 17-70 sigmas, except the 18-35 was so bad.
I think it was because it was a rental. And the rental shop didn't even have the dock available for adjusting. I had to just take it or leave it.

Thanks everyone. I think I'm going to go with my gut and use the Dot Tune method. It astounds me how little information there is considering how many people and reviewers rave about the Dock. I will make a video to share my experience once done. If anyone else wants to chime in, it'd be appreciated.

Aressem wrote in post #17078486
Unfortunately this doesn't help me much the dock allows 16 MA variables.

Yes you have 4 settings for subject distance times 4 focal lengths. Like I said, use your 7D AFMA with a close subject near MFD and test. Dot tune works but I personally like to take a shot using live view contrast detect and compare to Viewfinder phase detect results. If it is softer via phase detect, then compare the best of about 5 shots at -20,-15,-10 up to +20 and pick the sharpest MA. Then fine tune + or - 5 by ones. Then test on a subject about 50 times focal length and see if the same AFMA value is the sharpest.

If the numbers are not the same, then you have a slope issue that could not be fixed without sending the lens to be calibrated in the shop before the new dock. Now you can program the slope back in. So say at 18mm you find -10 at MFD and then moving out its -6, -2, +2. Now the slop of +4 is in. Remember this is just like alegebra calculating the slope of a line y = mx +b. The AFMA in Canon cameras can only adjust the zero point. If your slope is not off, I wouldn't bother with using the dock.

You then repeat for 24mm, 28mm and 35mm.

FEChariot wrote in post #17079287
If it is softer via phase detect

A note to save you a "doh!" moment; make sure you've enabled mirror lockup when taking the viewfinder/phase detect shots; the slap of the mirror (which is of course already up in Liveview) can make the viewfinder shots subtly softer, even if you've nailed focus. I spent a good few minutes scratching my head once over that, before realising my mistake.

Edit: by "you" I of course mean anyone trying this process that hasn't done it before

Aressem wrote in post #17078992
Thanks everyone. I think I'm going to go with my gut and use the Dot Tune method. It astounds me how little information there is considering how many people and reviewers rave about the Dock. I will make a video to share my experience once done. If anyone else wants to chime in, it'd be appreciated.

The software has minimal functionality and does nothing to assist you in the calibration process. You are basically on your own. Luckily my copy needed a minimum of adjustment on my 60D. With 16 different setting to adjust for its a very very time consuming process. You may also find that while at say f/4 the AF is spot on almost of the time, at f/1.8 the AF is less consistent, sometimes front or back focusing just a bit.. The dock won't do much to correct that since the corrections are based on focal length and distance, not the aperture used. What aperture were you using to test the lens? If you were wide open, I would stop down to at least f/4 and see how it performs at that aperture.

mwsilver wrote in post #17081306
The software has minimal functionality and does nothing to assist you in the calibration process. You are basically on your own. Luckily my copy needed a minimum of adjustment on my 60D. With 16 different setting to adjust for its a very very time consuming process. You may also find that while at say f/4 the AF is spot on almost of the time, at f/1.8 the AF is less consistent, sometimes front or back focusing just a bit.. The dock won't do much to correct that since the corrections are based on focal length and distance, not the aperture used. What aperture were you using to test the lens? If you were wide open, I would stop down to at least f/4 and see how it performs at that aperture.

Considering I plan on using it a lot wide open, I will likely calibrate it at f/1.8.

Aressem wrote in post #17081711
Considering I plan on using it a lot wide open, I will likely calibrate it at f/1.8.

I tried that. I hope you have better luck. At f/4 AF is dead on 95% of the time. At f/1.8. that percentage drops down to 65 to 70% depending on lighting, the size of the subject target, and the contrast of the subject. Larger, high contrast subjects do much better. When shooting wide open I try to focus on a point on the target when there is a sharp contrasting edge, if I can. The hit rate goes up significantly. When stopped down, the hit rate is similar to my slower Canon lenses. For what it worth, the AF hit rate wide open with my Canon 50mm f/1.8 isn't much better. When I have lighting issues that impact the Sigma's AF, there is always live view, which is not affected, and of course manual focus.

Sorry to piggyback off your thread but I just tried calibrating mine and here are the results I got

Nivekolleh wrote in post #17083308
Also how did people adjust theirs at near infinity, I have mine set at 80" but it's hard to tell if it's back or front focusing at all

As I posted earlier:

gremlin75 wrote in post #17078670
I calibrated my 18-35 with the dock manually.

Basically I just set up the target at each distant shown in the calibration software. I'd Take a shot, switch to live view, zoom in on live view and manually focus the lens to get proper focus (to check for front or back focus). I'd do this several times to make sure it was infact front or back focusing.

If your camera doesn't have live view then you'll have to get a target that will show if there is front of back focus. This one worked ok but I found my live view method worked better for me. I have never used "dot tune"

Your 18mm settings seem all over the place to me. I'd go back and re-test them.

Nivekolleh wrote in post #17083308
Sorry to piggyback off your thread but I just tried calibrating mine and here are the results I got

it seems like too much in some spots, at 18mm, i'm still getting shaky results sometimes, so i let it go for the day and will go back to it tomorrow.

Does this look right to anyone?

Also how did people adjust theirs at near infinity, I have mine set at 80" but it's hard to tell if it's back or front focusing at all

It will vary depending on the body its mounted on and even the specific copy of the lens.