Canon 6D and Sigma 35mm Art 1.4 not compatible?

Hi everyone. I keep banging my head against the wall with my Sigma 35mm Art 1.4. I am well aware of the notorious issues of soft focus with this lens but I'm stubborn and keep trying to make it work. Not sure if calibration would help since it can be so inconsistent.

Here are my latest test samples. I chose my daughter this time since I usually shoot people but I have done numerous tests over the last few months, people as well as stationary objects. It seems to focus most terribly on faces, especially if more than 7-8 feet away, but it is hit or miss with objects, too. Mounted to tripod, F2, SS 1/200, ISO400, 4 foot distance. I repeated twice, same result:

Photo 1: single focus point right over her eye (half pupil and iris, half white and eye rim). Seems soft and dark. Crisper on her shirt, to me.

Photo 2: for kicks, focused on her hair line right above the eye. Shockingly/not shockingly, it looks clearer than the first.

Photo 3: Live view focusing over half her face and hair. Seems clearest of all. Also brighter. Is that normal with Live View or does underexposure using viewfinder (meter said it was properly exposed) indicate a lens problem?

Thoughts? Contact Sigma for repairs? Throw it in the trash? It's so frustrating. I appreciate anyone reading all this and can help.

 

Hi there, thanks for taking the time to help me. You're right the tripod did move forward between photos a tad, to give more space between me and the wall lol. Not by much, an inch or two. I used 2 second timer, tripod didn't move during shots. I used One Shot, not Servo and I rarely use focus and recompose, definitely didn't here.

Ok so maybe I'm expecting too much of this lens. I think you're saying, bring subject closer if shooting wide open or stop up if shooting a few feet away or more. Correct?

 

Oh I just got a reply back from Sigma repair, who I also reached out to:
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New reply:


Hello,



We usually see problems with focus error on Canon bodies because the sensor setup differs from one copy to the next, much more so than with Nikon. Also, fast servo modes and multipoint focusing can cause this as well.



We often do custom calibration of these lenses to customers' Canon bodies because of this. If your body has an AF micro-adjustment feature you may be able to correct this yourself. Otherwise, please send the body as well if you can and we will correct this here, please see below.



Package the product and relevant accessories carefully, using ample padding materials and a sturdy mailing container to prevent damage in transit.
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I'll try MA and see how that goes.

 

My thoughts on this is that they look a little soft. I am wondering if the lens is front focusing a little bit.

No, don't do that.

I'm hearing you.

This lens should be giving you sharp images. Just out of curiosity, when you used live view to focus, did you use the cameras AF? If yes, are you able to take an image of something using live view, and you focus the lens manually using x10 magnification, camera on a tripod. And can you let us know how sharp the image is on the point that you focused on. My line of thinking is to try and rule out any optical problems with the lens for starters.

Gary

 

Welcome o the forum, Shannon. not much more I can add to the comments, that would be helpful, the members who have given advice are knowledgeable and worth taking in what has been suggested. All the best with it.

 

Hi Gary, thank you for your comment. I forgot to mention that; I used AF when in live view. Good idea to try manual - I'll do that in the morning when I have better light and will report back.

 

i think the live view image reveals the culprit as i expected it would when reading the first two descriptions,
do you know how to do the focus adjustment using a ruler at 45 degrees to the lens head on?

 

Ok, so I was busy this morning. At both Sigma Repair's and Caladina's suggestion above, I did a microadjustment using an online focus sheet I printed off. It was indeed front focusing. After adjusting it a whopping +18, it seems to have fixed it based on the results I took with the focus sheet.

Unfortunately, I don't think that's the only issue. I took some more test shots, first of an orchid at different distances (8 inches for near, 2 feet for medium, 4 feet for far) using both AF center point as usual, as well as manual focus using 10x magnification at Gary's suggestion. I used AV mode at F1.4, which I realise is going to be no sweet spot for any lens so consider this a bit of a stress test. I still think AF is giving softer focus compared to manual...the farther it gets, the worse it gets to me. The far shot, with AF, I had to take it 3 times to get any kind of reasonable focus (despite it "beeping" saying it focused). However, even 8 inches away, the focus on the pistil of the orchid on the left (our left), which was my focus point, seems off...looks like it grabbed focus more on the pistil to the right, which seems impossible to me but yet it did. Yes, I used a tripod, 2 second timer. What do you think?

Photos are here: https://www.flickr.com/photos/187947193@N07/shares/YnR166

I also took some shots of my daughters again (same link). Not on a tripod but I wanted something more realistic since I am usually not taking photos of my family with a tripod as I prefer more documentary style. For this I stopped down to F2.2 and F2.5 (each daughter respectively), which is still wide, I know, but given the lighting in my house, it is what it is. They all appear a bit soft to me still although the closer ones seem slightly better than the farther ones. And again, maybe I expect too much but I figure a $1100 CAD 1.4 lens should not be that soft at F2.2 and F2.5.

I think this lens and AF just does poorly with anything that is not high contrast or high colour....which is bad particularly for photos of people since faces usually don't have a lot of contours or contrast.

 

Hi Johnsey, thank you. I forgot to reply back to you yesterday...the photo you posted above of my daughter with the cross point, that's the photo in which I focused on her hair line exactly above her eye, right where the crosspoint in your photo meets. I did that as a bit of a test, since it's higher contrast than the eye. It seems a bit sharper to me than when I focused on her eye. I know the DOF will not be much at F2 but even focusing on her hair above the eye, at 4 feet away, it should've given me at least 1-2 inches in sharp focus, no? Least that's according to my DOF app lol.

 

if you test it with a diagonal ruler then you will see exactly how much it is out, use both mirror and live view, live view should be spot on the millimeter you focused on

 

Hi Caladina, I only have a metal ruler, which doesn't really work, I used the focus test sheet instead. It was at a diagonal. Like I said, it was front focusing, which MA seemed to fix but pretty sure it just has inconsistent focus altogether, unless it's focused on a large (or close), contrasty, colourful object. I realise AF systems need some contrast but this lens seems way more particular than any others I've used.

*Edit: I just realised that the post I posted this morning about my updated tests shots is still waiting mod approval...maybe because I linked my flickr account (with the test shots).

 

is it inconsistent in live view as well as mirror view (sorry not sure what you call it when its shot with the mirror down, i guess to dslr shooters its called normal mode)

 

No it seems spot on using manual live view (I didn't try AF live view), but AF in view finder is soft or refocuses elsewhere. My post with all the photos is still awaiting moderation unfortunately.

 

Yeah +18 is definitely a lot...I adjusted by only 5 at first and then went up in increments of 5. +10, it was still front focusing, +15, slightly better, +18 seemed to get it right.

Is an unsharp mask applied in camera? I have done no edits to those other than exporting to JPEG via Lightroom. There is the "sharpen for screen" checked.

Edit: forgot to respond to your other question, I don't think my other lens has issues, no but the trouble is it's not a fair comparison. My only other lens is a F4 75-300mm zoom lens, which I rarely use. I did take some test shots with it this weekend too and it seems ok.