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Archive 2013 · Sigma USB Dock in Stock for $59!
  
 
badlydrawnboy
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Okay, I just watched the video. Can someone tell me if I'm understanding the process correctly?

I have only one body (5D3) and I'll be using this with the 35. So I would use Focal or Dot Tune to calibrate the lens at four different focus distances: 0.3m, 0.4m, 0.7m and maybe 3m (hard to tell using the scale on their video). I write those values down, but I leave the MFA settings on the camera at 0. Then I attach the Sigma 35 to the dock, and enter the MFA adjustments for each focus distance that I determined with Focal or Dot Tune.

If that's indeed how it works, sounds pretty cool to me—especially because the issue I was having with the first two copies of the Sigma 35 that I tried is that it would nail focus at one distance given a particular MFA value, but not at another. i.e. with an MFA of -3, close-up shots <1m would be in focus, but shots >1M wouldn't be. If I changed the MFA value to -6, it would be the opposite scenario.

So I, for one, am excited about this. The downside would be if I had multiple camera bodies, but I don't and don't anticipate that ever changing.



Jun 06, 2013 at 05:31 PM
austin.grant
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That sounds correct to me. The cool thing is that I think you'll be fine with different camera bodies. Once the lens is adjusted to have a consistent MFA across the focus distances, it should only take a single MFA for each unique camera to make everything work perfectly.




Jun 06, 2013 at 05:39 PM
Photonic
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badlydrawnboy,

You've got it. This entire approach, however, is predicated on their being a perfect correlation between a camera body MFA adjustment step and the Sigma lens MFA adjustment step. Everyone is hoping this will be the case. I am on record as having doubts but will be the first one jumping up and down if I am wrong.



Jun 06, 2013 at 06:47 PM
Lasse Eriksson
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Photonic wrote:
badlydrawnboy,

You've got it. This entire approach, however, is predicated on their being a perfect correlation between a camera body MFA adjustment step and the Sigma lens MFA adjustment step. Everyone is hoping this will be the case. I am on record as having doubts but will be the first one jumping up and down if I am wrong.


But why would you belive the Sigma and Canon don't work together, And at the same time you belive the FoCal and others are have a perfect match with Canon MA



Jun 06, 2013 at 06:54 PM
austin.grant
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Lens just arrived, dock is out for delivery. I've got a gallery opening including some of my astrophotography this evening and an out-of-town wedding to shoot this weekend, but I'll get to test the dock extensively on Sunday. I'll post an in-depth write up at that time.

In the meantime, what's with this "guilty until proven innocent" attitude? Lets be optimistic here and assume that Sigma has done their homework on this one. There are no points awarded either way, so no use setting up for a "told you so."



Jun 06, 2013 at 07:10 PM
JohnDizzo15
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Lasse - I think Photonic's concern is that the adjustment dock values may not exactly equate to what the canon values are. i.e. would +1 be exactly the same amount of adjustment through the body's AFMA as it would through the dock and into the lens directly.

This is a valid question although my belief is that Sigma would have extensively tested this already before putting the dock to market.

As far as trusting FoCal or other software equivalents, the answer is simple. You are testing a particular lens with a particular body. The software is measuring for that exact setup and telling you exactly what changes need to be made based on the test shots it takes with that body/lens combo. You are then putting that value into where the software intended the value to go as opposed to making the changes through another software (Sigma's), entering the value into another device (lens), via another device (dock). The question Photonic has is different from this in that he wants to know whether the values are identical since you are now introducing additional elements into the equation.



Jun 06, 2013 at 07:21 PM
Photonic
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Another thing just occurred to me. Normally we use MFA to "fine tune" a given camera/lens combination for normal variations in each.

The Sigma 35mm lens has the ability to fine tune focus at four different focus distances. Given the UI screen shots for the Sigma software that comes with the dock I am going to assume that all lenses will have a default setting of zero from the factory. I am guessing that this offset sits on top of a factory calibrated base number for that lens which varies from lens to lens and that we will never see. To assume otherwise would suggest that Sigma is giving us the knobs and saying "you finish the job, we couldn't be bothered" (OK, perhaps that was too snarky).

I am going to assume that Sigma gives us the best four base numbers they can for each and every lens using equipment far more sophisticated than available to us to stand in for the camera body during calibration. The fact that they give us access, by way of the dock, to all four knobs rather than a single global offset knob suggests that there is benefit to fine tuning each number.

If that is the case, and you do not adjust all four numbers by equal amounts, then I think you are going to want to calibrate all four numbers to each body you use which brings me back to the original concern which drew me into this thread.

In my mind there are two big questions remaining on the table and we are possibly hours away from definitive answers:

(1) Do body MFA steps = lens MFA steps. If yes, then Dot Tune of FoCal can be used to greatly diminish labor. If no, we are going to need snapsy to come up with a new miracle time saver or deal with a very tedious process indeed.

(2) Once a lens has been calibrated on one body, are these numbers also optimal on additional bodies using the camera's global MFA adjustment. If yes, then lens switching per normal. If no, then lens switch accompanied by docking and download of new numbers each time.

Should we have a prize for the first to perform the experiments needed to answer these questions?



Jun 06, 2013 at 07:38 PM
Photonic
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Sorry to all if my tone is coming off as pessimistic. I am truly hoping for success. I am a big Sigma fan and have plenty of there glass to show for it (including a new 35mm that I just picked up on B&S)

I have always tried to push back on vendors to help them put their best foot forward. I pushed on Canon when I made the switch from the Canon 300mm f/2.8 IS to the original Sigma 120-300mm to give us a zoom in this very useful range and aperture. I pushed on Sigma to add image stabilization and give us a true 300mm at normal focus distances (we eventually got the former). At the time I was derided for saying that the 120-300mm was in the same league as the Canon. Have a look in the Canon 200-400mm thread. Seems that many are now prepared to acknowledging the IQ on the Sigma when faced with the price tag from Canon.

In any case I will try to be more positive and give Sigma the benefit of the doubt.

Edited on Jun 06, 2013 at 07:58 PM · View previous versions



Jun 06, 2013 at 07:42 PM
Lasse Eriksson
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JohnDizzo15 wrote:
Lasse - I think Photonic's concern is that the adjustment dock values may not exactly equate to what the canon values are. i.e. would +1 be exactly the same amount of adjustment through the body's AFMA as it would through the dock and into the lens directly.

This is a valid question although my belief is that Sigma would have extensively tested this already before putting the dock to market.

As far as trusting FoCal or other software equivalents, the answer is simple. You are testing a particular lens with a particular body. The software is measuring for that exact setup
...Show more

Yes I understand that. But Sigma have a different dock for each brand and lens-mount. They also have +20 and -20 adjustment exactly like Canon.
Do you really belive they have not tested and tried it together with Canon bodies? And that they just made up some numbers that are very different from Canon's? So everyone making adjustment will get it wrong? Because +5 in sigma would be like +12 or +9 with Canon?



Jun 06, 2013 at 07:43 PM
badlydrawnboy
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I had the same thought re: other bodies. The solution austin proposed, which of course may work, assumes that the adjustment required at a given focal distance on the lens would change equally with a new camera body. Let's say that on my 5D3 I adjusted the lens to -3 (0.3m), -2 (0.4m), -1 (0.7m), 0 (3m). Then let's say I mount the lens to another body, choose the 3m focus distance, and find an in-camera MFA value of +2. But as Photonic suggests, why would we assume that the +2 at 3m required by the new camera body with this lens would also be the adjustment required at 0.3m? The very fact that it's possible to adjust at these different focus distances suggests that they're not equivalent.

Anyhow, it doesn't apply so much to me because I don't have more than one body. But it's interesting.



Jun 06, 2013 at 07:47 PM
 

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austin.grant
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Different MFA numbers for different focus distances should represent a lens issue, so effectively normalizing that MFA in lens should allow a single MFA for each body to account for the remaining lens/body issue.


Jun 06, 2013 at 07:58 PM
Photonic
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If it is a lens issue, then why does it not come from the factory adjusted perfectly?


Jun 06, 2013 at 08:00 PM
Photonic
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If these numbers are strictly used to correct a lens issue (no dependence on body) then I would have preferred that Sigma got them right at the factory. Certainly they should have something better than my new favorite method (Dot Tune) to make the adjustment.

If there is dependence on the body then we are going to need to reload numbers with each body switch, something that would not work for me personally.



Jun 06, 2013 at 08:20 PM
JohnDizzo15
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Lasse Eriksson wrote:
Yes I understand that. But Sigma have a different dock for each brand and lens-mount. They also have +20 and -20 adjustment exactly like Canon.
Do you really belive they have not tested and tried it together with Canon bodies? And that they just made up some numbers that are very different from Canon's? So everyone making adjustment will get it wrong? Because +5 in sigma would be like +12 or +9 with Canon?


Please see second paragraph of my previous post in response to your question of whether I believe they would do that. So in case explicit answers are necessary, the answer is no, I don't believe they would send it into the market without extensively testing and ensuring that it works. I was merely stating that it was a valid question for curiousity's sake.


Edited on Jun 06, 2013 at 08:44 PM · View previous versions



Jun 06, 2013 at 08:42 PM
Photonic
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Again, I apologize if I am being too ardent. The fact is that I am hoping to send a message to the folks at Sigma and this thread was simply the conduit I found to voice my concerns.

I love the IQ on my 120-300mm OS. I like the new "S" version of this lens even more because of the sleek new industrial design (totally fair to call me out on this very superficial attraction), "splash-proof" weather sealing, improved tripod collar foot (rarely appreciated by anyone who has not handled the lens), and the ability to download new firmware with the dock.

I am not happy that Sigma saw fit to increase the price so dramatically for what is largely a face lift (the optical formula old to new is identical). Once they added the USB interface (needed to address legitimate concerns about future body incompatibility), I think their marketing folks went overboard trying to "invent" new benefits they could hype in order to help justify the price increase. The message I want Sigma to hear loud and clear: "Don't abandon the value franchise on which you built a good business." I know they must be tempted to look for any excuse to raise prices when Canon puts their 200-400mm zoom on offer at $12K.

Glad I got that off my chest.



Jun 06, 2013 at 08:42 PM
JohnDizzo15
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And as far as it being a lens issue or needing it to be set to "0" from the factory. That is impossible as not even OEM lenses meet that standard. It has been extensively discussed here and elsewhere that tolerances are an evil of all bodies and lenses. It is even more difficult with non-OEM glass as they are backwards engineering the AF which Sigma techs will tell you themselves. The fact that they have given us a fighting chance to calibrate these lenses to our individual needs is great so long as it works as well as expected.


Jun 06, 2013 at 08:49 PM
austin.grant
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JohnDizzo15 wrote:
And as far as it being a lens issue or needing it to be set to "0" from the factory. That is impossible as not even OEM lenses meet that standard. It has been extensively discussed here and elsewhere that tolerances are an evil of all bodies and lenses. It is even more difficult with non-OEM glass as they are backwards engineering the AF which Sigma techs will tell you themselves. The fact that they have given us a fighting chance to calibrate these lenses to our individual needs is great so long as it works as well as expected.


+1 Exactly



Jun 06, 2013 at 09:03 PM
Wahoowa
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JohnDizzo15 wrote:
And as far as it being a lens issue or needing it to be set to "0" from the factory. That is impossible as not even OEM lenses meet that standard. It has been extensively discussed here and elsewhere that tolerances are an evil of all bodies and lenses. It is even more difficult with non-OEM glass as they are backwards engineering the AF which Sigma techs will tell you themselves. The fact that they have given us a fighting chance to calibrate these lenses to our individual needs is great so long as it works as well as expected.


+2



Jun 06, 2013 at 09:45 PM
Pixel Perfect
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Jeffrey wrote:
Trying to understand why this technology would not work on Canon lenses as well.


Same reason I can't plug my external engine computer from my Ford into my VW.



Jun 06, 2013 at 10:23 PM
Photonic
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John,

We are of one mind about the ability of a lens maker to get the lens perfect in the factory.

The "zeros" I was referring to were the values stored in the user accessible MFA registers when you get your lens from the factory and plug it into your dock for the first time (totally different concept). I am guessing that these come up zero when you first connect the dock to the lens.

Given that the lens has a mechanism to turn 4 numbers into MF adjustments for different focus distances, I think it is highly likely that Sigma uses this same mechanism to do their factory calibration of each lens. They simply use four registers which are not visible to the end user to store the factory calibration values. If the user dials in an offset they simply add or subtract that number from the one they have already stored in the lens. A less elegant but entirely acceptable alternative would be if Sigma uses the User MFA registers to store the factory values. This can be quickly answered if folks find non zero entries after pressing the DEFAULT button in the application. No point debating this when an answer can be determined so easily.

My basic premise is as follows. Sigma has given users a mechanism to adjust MF at 4 different focus distances. I would find it very odd if they did not do their very best to put good numbers in as a starting point and call that the default. Whether they do this with a hidden register and an initially zero register for the user or with a single register is unimportant and can be answered by anyone with the dock.

Absent a technical spokesman from Sigma adding some clarity, I think we are not going to understand the value/level of effort needed to make use of the in lens MFA mechanism until we can answer the two questions I posed earlier in this thread.

Given that my new 35mm f/1.4 arrived just now I am going to play with that until some of the new dock owners can provide some real world feedback (even posting the documentation for the dock/adjustment software would probably be very informative).



Jun 06, 2013 at 10:54 PM
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