Saturday, November 9, 2013

My Trip to Sigma

Not having anything else to go on to solve my focus issues with the Sigma 120-300 f2.8 “Sports” lens and the Canon 1D, I decided to make the trip to Ronkonkoma Long Island. My hope was an in-person dialog with the service department as they looked over my lens would get to the bottom of things.

First off, they were able to un-stick the front filter, swapped my emergency replacement brass tripod collar screws with nice standard Phillips head screws, and assured me everything was fastened in with Loctite. Then it came down to making adjustments in the PCB ROM not available using the USB dock.

It was interesting to find out that the dock actually provides more control over the focus adjustment of the lens than the factory adjustment software. The factory software apparently allows + and – adjustments to just the outer focal lengths (120mm and 300mm). Based on my earlier findings they programmed some additional “+” into the 120 end and some “-” into the 300 end. The goal was hopefully to lessen the large gap in the settings from +17 at 200 and -16 at 300.

To make a long story short, it didn't work. The reprogramming had no real effect on the 300 side, and just shifted the required existing settings over a proportional amount on the 120 side. The main problem of not getting accurate focus with the 1D Mk IV (and Mk III) in between 200mm and 300mm was still the same. Next they brought out another new 120-300 “Sports” lens to compare with mine. The results were the same with the new lens, so that confirms it's not some anomaly with my cameras. With that the service manager said he would be sending an advisory to their headquarters in Japan to have them investigate it more.

So was it a wasted trip? I guess I will have to wait and see if I get an answer back from Sigma Japan. I also don't think just shipping my lens to them with the Mk IV (and being without both for a week or more) would have convinced them as easily that there really is something to all this. I will say that I was very satisfied with the service and reception I got while I was there, despite the outcome so far.   I'm keeping my fingers crossed.

Friday, October 25, 2013

News From PhotoPlus Expo

I spent the day today in Manhattan at the PhotoPlus Expo.  Naturally a good bit of my time there was at the Sigma booth trying to shed some light on my Canon 1D and 120-300 f2.8 Sports lens issue.  The first rep I spoke with (name withheld) blamed it all on Canon saying that I should already know about all the horrible focus issues the 1D series has been plagued with.  Really?  Aside from the well documented issue in bright sunlight with the early 1D Mk III bodies I am not aware of any "focus plagues", especially when it comes to the Mk IV.  Aside from the fact that, as I mentioned before, my 1D Mk III and Mk IV focus perfectly on all my other lenses (including others from Sigma).  The second rep I spoke with was more reasonable.  After hearing my plight he invited me to personally bring my lens and all my camera bodies to their facility in Ronkonkoma, to see if the service department could figure it out.  I may just have to make the drive and take them up on that in the near future.

Next I went to speak with the folks at Canon.  A rep I have known there for many years (name also withheld) was able to help out a little.  Though he of course can't comment directly on the Sigma lens, he did confirm for me that the focus systems in the 1D Mk III and Mk IV are completely different from the rest of their cameras, in that they have an additional processor devoted just to the focus.  He also said that 3rd party lens makers don't always ensure full compatibility with high end "pro" camera bodies since they make up such a small segment of the market.  He used the example that, even on their least expensive lenses Canon needs to make sure they all can close down to their minimum aperture (say f22) perfectly at 12 frames per second.  Now that has nothing to do with the problem I am having with the Sigma, but does at least make some sense.  It does seem plausible that Sigma either was not able, or didn't bother to, properly reverse engineer the different focus system in the 1D cameras.  Maybe I am finally getting somewhere?

Tuesday, October 15, 2013

Initial Rant

Let me start by saying that this is not an official review of the Sigma 120-300mm F2.8 DG OS HSM | S, also known as the “Sports” version. There are plenty of reviews to be found online by people much more qualified at reviewing lenses than I am. The purpose if this blog is to voice some concerns I have with this lens, specifically when used on the Canon 1D Mk III and 1D Mk IV, and hopefully find out if others are experiencing similar things.

Before I get to the details I want to say that on the whole I absolutely love this lens. If you haven't noticed yet what Sigma is up to with their new “Global Vision” lenses I suggest you take a look. There are some truly innovative designs in the series, which are not only optically outstanding but solidly built. In addition, the level of customization available with the new lenses using Sigma's USB Dock goes beyond what any other manufacturer in the industry is doing right now. So with that out of the way let's get to the nuts and bolts of why I'm writing this blog.

Anyone familiar with Canon's professional and semi-professional cameras (starting with the 50D) knows that they have a built-in ability to fine tune the auto focus of the camera body to specific lenses (called auto-focus manual adjustment or AFMA). If you find a particular lens is consistently front or back focusing, you can “dial in” that lens using the AFMA to get accurate focus (+ or - 20 focus units from the camera body default of 0). If you use multiple camera bodies like I do (50D, 7D, 5D Mk II, 1D Mk III and 1D Mk IV), you will generally find most bodies and lenses have a certain “bias” towards back or front focusing, and will need some AFMA adjustment to get the most accurate focus.

Beyond the camera's built-in AFMA, Sigma goes even further by allowing the user to separately fine tune the auto focus of their new lenses using their USB Dock and Optimization Pro software. In the case of the new 120-300 2.8 “Sports” you can also adjust the focus speed, customize the optical stabilization (OS) and set the focus limiter range. Unlike Canon's global AFMA setting, the Sigma software allows precise focus adjustment of the lens at different spots in the zoom range, and different focus distances within that range. Below is a screen shot of the focus calibration window to give you an idea of the possibilities.

As you can see, focus tuning is possible (+ or - 20 units) at four spots in the zoom range (120mm, 150mm, 200mm and 300mm) and at four distance ranges for each focal length (minimum focus distance to infinity), making a total of sixteen user adjustable focus point settings. So if you have the time and patience (or are also a geeky under the hood compulsive type like I am), you can get the 120-300 2.8 “Sports” focus settings nailed down really, really well.

I will stop here a moment and back up a little so as to add some background to my story. In September of 2012 I purchased the older version of the Sigma 120-300 2.8 known as the EX DG OS APO HSM (not to be confused with the even older EX DG). Out of the box I had issues with that model not focusing properly on my 1D series cameras. Even on static subjects, at the long end I was only getting about 30-40% of the frames in focus. This was not an AFMA issue as I had carefully calibrated the bodies to the lens multiple times. Oddly enough, on the 50D, 7D and 5D Mk II my percentage of in focus images, even for moving subjects, was more in the 90% range (where it should be). That is all well and good, but I shoot a lot of sports and rely on the 1D series camera's voice tagging feature to keep track of plays, which helps a lot with writing accurate captions later on (the 50D, 7D and 5D Mk II have no such feature, and writing notes during a game is a real pain anyway).

I sent the lens back to Sigma with specific instructions and sample images hoping it just needed some adjustment. Sigma sent the lens back, saying there was nothing wrong with it, and did not perform any calibration or repair. They also said it must be a problem with my 1D cameras, and to just use the lens on my other camera bodies (really?). Next I had the focus on my 1D Mk IV checked and calibrated by Canon in Jamesburg, NJ. I also borrowed another 1D Mk IV from a colleague to test on the Sigma and got the same results as my own 1D bodies. Mind you, I was not experiencing any focus issues with my cameras using the Canon 70-200 2.8 L II and 300 2.8 L IS (or any of my dozen or so other lenses). I complained again to Sigma who, much to my surprise, offered to replace the lens outright with a new one (thanks!). By this time the new improved “Sports” version of the 120-300 2.8 had been announced, so without ever using the replacement lens I put it up for sale and put the cash towards the sports version once it was released.

I was very excited about the new “Sports” 120-300. It promised better construction, weather sealing, a focus limiter, and most importantly the USB dock. I want to put a gratuitous plug in here for Allen's Camera in Levittown, PA who, while others where still just taking pre-orders, got me one of the first of the new 120-300mm F2.8 DG OS HSM | S lenses that came into the U.S. (you are the best Allen). I was disappointed to find out however that the dock was not released at the same time, and was still another month out (by the way, not for nothin', but for the price of the lens they should throw in the $59 USB dock).

The first camera I mounted the new lens on was my 1D Mk IV (which had the focus calibrated by Canon a few months earlier). Right away I noticed that there was again an issue with the focus. No matter how I set the AFMA in the camera I could not get the lens to focus accurately through the whole zoom range. If I set the AFMA to focus accurately at 200mm, it would badly front focus at 120mm, and badly back focus at 300mm. I tried the lens on my 1D Mk III and got similar results. Then I tried it on my 7D and was able to find an AFMA setting that provided reasonably good focus through the whole zoom range (and the same with the 50D and 5D Mk II). Something is definitely up here. It seemed as though the one thing I was counting on being different with the new lens was exactly the same as the old one (UGHH!). So now I'm anxiously awaiting the release of the USB dock, telling myself that I will be able to get the 120-300 2.8 "Sports” dialed in to my 1D bodies perfectly, and all will be right with the world. Do I have to say “guess what”?

The dock finally arrived. Knowing 200mm and an AFMA on my 1D Mk IV of -10 was about the “middle” of the focus range, I began tweaking the focus of the new lens from both ends. I adjusted the front focus issue at 120mm back, and adjusted the the back focus issue at 300mm forward. After many hours of continuous testing I arrived at the following settings:

The good news is that the AFMA on the camera is right in the middle at “0” now. Here's the bad news. Notice that starting at 120mm and up to 200mm the focus adjustment follows a relatively straight progression from +3 to +9 to +17. Then, at 300mm it swings all the way in the opposite direction to -12 and -16. This explains why, at the default settings of “0” across the board, the lens was front focusing at 120mm and back focusing at 300mm. So what's the big deal you may ask? The lens is dialed in either way right? Unfortunately not. Despite each of those individual focus points being dead on, in between the focal lengths of 200mm and 300mm, on the 1D Mk IV the focus is way off (about 15 AFMA units off).

So I went through the same procedure with my 1D Mk III, and here are the settings that worked for that camera:

Notice they are very close to the 1D Mk IV with a similar wild swing from +20 at 200mm to -16 at 300mm. The big difference is the in-camera AFMA of -9, but the rest of my lenses on that camera body all need an AFMA in the “-” range, so that explains that. There is also the same issue with the focus being way off in between 200mm and 300mm. Now it gets interesting. It took me several days, but I went through the same testing on the 50D, 7D and 5D Mk II. Here is what I came up with:

 The in-lens focus calibration settings are in no way at all similar to the settings I found for the 1D cameras. In fact, they range from the + side at close distances for all focal lengths, to - settings at infinity for all focal lengths. Additionally, with AFMA settings between -6 and -10, the lens focuses extremely accurately on all three cameras, even in between 200mm and 300mm. With these settings on my 7D the lens performs so well, even at f2.8 with fast moving sports, I haven't used my Canon 300 2.8 L IS since getting the Sigma dialed in.

What's going on here? I had the same experience with two different models of the same lens. My 50D, 7D and 5D Mk II are no problem, but forget about using it on the 1D series cameras. Part of the reason may be explained in an excellent article written by Roger Cicala at When they disassembled both the “OS” version of the 120-300 and the “Sports” version of the120-300 side-by-side they found the circuit boards to be essentially the same. Does that mean it is a programming issue in the PCB?

Let me add some more interesting facts into the mix. Besides Sigma's 120-300 2.8 “Sports” lens, I also own their APO 50-150mm F2.8 EX DC OS HSM (perhaps one of the most under-rated lenses around). Though it is a “DC” series lens, meaning it is designed for APS-C size sensors, it also fully covers the larger APS-H size sensor of the 1D series cameras (not to mention it is an excellent compliment to the 120-300). On all my cameras (including the1D Mk III and 1D Mk IV) the 50-150 focuses extremely accurately all the way through the zoom range at all distances with just slight in-camera AFMA adjustments. Even though it does vignette badly on the 5D Mk II, it still focuses accurately. I also used to have Sigma's older EX DG 12-24mm f4.5-5.6, and EX 14mm f2.8 which focused fine on all my cameras.

So here are my ultimate questions. What is different about the auto focus system in the 1D models compared to Canon's other cameras? Why is this issue happening only with the Sigma120-300 2.8 and not other Sigma lenses (assuming they use the same reverse-engineering for everything)? Is this some secret ploy by Canon to make you only buy their lenses if you use their “professional” cameras? Would adding a focus adjustment setting at 250mm in the Sigma Optimization Pro software fix the problem? (probably not considering the vast difference in settings already between camera types) Why isn't there a setting for 250mm in the first place, when there are small jumps from 120 to 150 to 200, and a big jump from 200 to 300?

If you have had a similar experience with Canon cameras and Sigma lenses, or if you are able to shed any light at all on my dilemma (especially if you happen to work for Sigma or Canon), please leave a comment.


In addition to all of the above (which turned out to be way longer and more complicated than I initially wanted) there are a few more issues with the Sigma 120-300mm F2.8 DG OS HSM | S that I'd like to share. Though not a huge deal, they are things I think Sigma should be made aware of.

Tripod Collar:

In general the tripod collar is an improvement over the older version in that it has loops for a strap positioned at 5 o'clock and 7 o'clock, as opposed to a single loop at the back elbow of the collar (though I wish they had kept the beveled cut on the bottom like the old one which fit nicely in a Acra Swiss head without an adapter). About a week into owning the new lens I was using it on a monopod and went to turn the camera vertically. I heard a terrible scraping sound and the collar froze up. After several minutes of wrestling with it I managed to get the collar off and found one of the screws holding the collar guide pins had come out and scraped along the inside, badly scratching the lens barrel. 
 Scratched barrel and replacement brass screw

Though I was mad now that my brand new lens had a nice scratch on the barrel, I figured no problem since I would just screw it back in. Nope. Instead of a standard Phillips head screw Sigma used a five pointed Torx type screw (just like Apple uses on the MacBooks and iPhones, called a pentalobe). Well, I don't have a pentalobe set of screwdrivers, and neither does any hardware store I could find. When I checked the other screws under the tripod collar I found they were all backing out, and could be unscrewed completely with just my fingers. Since I couldn't get the proper screwdrivers I did the next best thing and replaced all the screws with brass slot-head types of the same thread size I found in a hobby store. I also used Locktite to put them in, but if they happen to back out at least I will have the screwdriver I need to tighten them again.

Front Filter:

The Sigma 120-300mm F2.8 DG OS HSM | S unfortunately does not have a drop-in filter slot like Canon's and Nikon's big lenses. I think this is mostly because the lens has so many elements moving around inside, and not a lot of real estate on the barrel because of the zoom ring, that there is no room for one (other big Sigma lenses do have drop-in slots). The front of the lens takes a 105mm screw in filter. Sigma makes filters in many sizes, including 105mm, and they are not only excellent, they are a real bargain compared to the price of other high quality filters. I purchased their 105mm UV to protect the front and put it on as soon as the lens came out of the box.

The other day I noticed a few specks of dust behind the filter (and being the already aforementioned compulsive type I wanted to blow them out). I started unscrewing the filter (which I made a point of not initially screwing in too hard) and ended up removing the entire front element assembly along with it. Under the assembly are a bunch of brass shims which I had a bit of a time getting back into place before screwing everything back in. Now, of course, I have a few specks of dust inside the lens as well as behind the filter (which is now good and jammed on, and won't come off).

Some Good Things To Say:

I said at the top of this long rant that I really do love this lens, and there are many good things to say about it. So here is a simple list:

  • It's SHARP!!!
(if the Canon 300 2.8 L is a 10, the Sigma is a solid 9 and has a zoom)

Uncropped 7D frame of the Jets Nick Mangold
 100% crop (shot at f2.8)

  • It's built like a tank
  • The focus and zoom rings are nice and smooth
(and go the same direction as Canon's lenses do)
  • It works really well with the Canon 1.4x III (despite what Sigma says)
  • The OS is REALLY good, at least a stop better than Canon's
  • It's cheaper than Canon's 300 2.8 L by a mile (and has a zoom)
  • The customization options are very cool 
Understand that I'm not trying to discourage anyone from going out and buying the Sigma 120-300mm F2.8 DG OS HSM | S. Since I haven't been able to find anyone else complaining of the same Canon 1D focus issue, I'm wondering if my lens is just an anomaly (despite the similar problems I had with the first one).

As I get any more information, or maybe even a solution, I will post it here.