Sigma 50mm f1.4 EX DG HSM....are they any good?

[Craig Richardson]

EDIT 2: Lens is completely unpredictable, would not recommend at this point.

One thing I noticed about mine was if the camera is not steady (i.e. good handhold technique) I will often get both motion blur and OOF. It's as if the AF can't deal with much camera motion and still do its job. Only an issue at low aperture values.

Another thing I'm going to try even though I'm having good luck with this lens is shooting in AI servo mode when at low aperture values due to the very thin DOF. Several folks are recommending this in the Canon vs Sigma 85mm thread and it makes alot of sense. May be worth a try for you.

I can't get my head around how a lens can be so out of focus (like -11 needed to take a picture of the CN Tower because of back focus) but the phase detection can declare it in focus. What exactly did Sigma have to do to reverse engineer this focusing system? I also don't understand how this switches to front focus under 10 feet... or why when I use high quality B+H UV, CPOL, or ND filters the focus problems sometimes reverse themselves. Gentec has alot of work cut out for them when I bring this thing back again to them.

EDIT: I have done some light reading and came up with this gem:

When you half-press the shutter release (or the * button, if you've used the custom function to move focusing control there), the activated AF sensor "looks" at the image projected by the lens from two different directions (each line of pixels in the array looks from the opposite direction of the other) and identifies the phase difference of the light from each direction. In one "look," it calculates the distance and direction the lens must be moved to cancel the phase differences. It then commands the lens to move the appropriate distance and direction and stops. It does not "hunt" for a best focus, nor does it take a second look after the lens has moved (it is an "open loop" system).

If the starting point is so far out of focus that the sensor can't identify a phase difference, the camera racks the lens once forward and once backward to find a detectable difference. If it can't find a detectable difference during that motion, it stops.

Source: http://www.zen20934.zen.co.uk/photography/Canon%20AF%20System.htm

So what basically happens is that when the camera gives the instruction to the lens to move, the Sigma lens understands that it is a move order but does not move precisely enough. Because there is no second check on focus, errors are left uncorrected. This is why AI-SERVO seems to work better because the camera is constantly looking at the focus and making corrections, it creates a closed loop and errors eventually reach zero, or so you would think!

This also explains the strange pulsing behavior of this lens in servo mode because the camera is expecting the lens to nail focus after the first move order, but it doesn't so therefore the camera thinks the subject must have moved so it calculates a delta for subject shift and comes up with a move solution and tells the lens to execute, which it does but the lens screws up again, and so on and so on.

Another update: AI Servo works really well.

 

[skitron]

Another update: AI Servo works really well.

That's good to see. I'm having pretty good luck out of mine but this looks like it should make the percentages even better, plus maybe it works using a filter.

BTW, I get the same "pulsing" sensation with my 100 L when in servo, so it's not a Sigma specific thing. It's a bit smoother but definitely there.

 

[smirkypants]

I have the lens and I like it. Don't love to bits, but like. But this post isn't about that.

Here's something to consider. I do almost exclusively outdoor shooting and have several expensive ND filters to be able to hit the max 250 flash shutter sync speed wide open (yes, I know, I should have bought a variable to begin with, but didn't), plus a graduated ND and a polarizer. These were all 77mm because I own a 70-200/2.8, a 17-55/2.8 and a 100-400. I have other sized filters, but my big money is in the 77s.

So I was going back and forth on the Canon 1.4 vs. Canon 1.2 vs Sigma 1.4 when it occurred to me that the Canons use 58mm and 72mm, respectively and the Sigma 77mm. To be honest with you, this made it an easy decision for me. First, I didn't have to buy a bunch of new filters that may have doubled the cost of the lens, and second I didn't need to add weight to my camera bag.

It's something to consider.

 

[whatta]

Here's something to consider. I do almost exclusively outdoor shooting and have several expensive ND filters to be able to hit the max 250 flash shutter sync speed wide open

could you show me few examples (pictures) of this technique? I wonder what is it for. : Thanks a lot.

 

[catz]

I have Sigma 50 mm 1.4 EX DG with 5D mark II.

- It is a good lens (I am going to keep it)
- However, it is not perfect:
- All Sigmas have a bit less neutral color balance compared to Canon L. The 50 mm Sigma is no exception. It must be lens coating or something, but similarly than 12-24 EX DG, this 50 mm has a slight tint into yellowish.
- There is some chromatic aberration on out of focus areas, more than for example in Canon 70-200 2.8 L IS USM.

I have sort of stated to love the neutral (non-tinted) look of Canon L, and I think the only lens I would possibly trade this Sigma would be Canon 50 mm 1.2L. It is very expensive so not going to happen anytime soon.

I love the 50 mm on full frame since it is useful as general purpose lens. On crop sensor I could find hardly use for the lens except for maybe portraits. I can do even landscapes with this on full frame.

I have tried the lens on 60D but I was dissatisfied with the field of view.

For crop sensor a good alternative lens for giving 50 mm field of view is Samyang 35 mm F1.4. It has similar performance than the Sigma and has the best manual focus ring of the lenses I have used. It has also build quality and robustness comparable to a big Canon L. I don't think the 50 mm Sigma is a good choice for crop sensor unless you are looking 75 mm field of view (which incidentally I get out of my 70-200 on full frame which has more neutral color balance IMHO).

 

[JR]

"" I think the only lens I would possibly trade this Sigma would be Canon 50 mm 1.2L""

I had the Sigma 50 1.4 before buying the Canon 50 1.2L a little over a year ago. Overall I found color rendition to be better with the L lens then with the Sigma one...Now because it is much heavier then the Canon 50 1.4, not sure I would get the Sigma over the Canon 1.4 if I did not have the 1.2 already.

 

[smirkypants]

Here's something to consider. I do almost exclusively outdoor shooting and have several expensive ND filters to be able to hit the max 250 flash shutter sync speed wide open

could you show me few examples (pictures) of this technique? I wonder what is it for. : Thanks a lot.

I think that's probably way beyond the scope of this thread, but here's a link to the strobist web site that explains how the process is done: http://strobist.blogspot.com/2010/06/using-nd-filters-to-kill-depth-of-field.html

 

[skitron]

For crop sensor a good alternative lens for giving 50 mm field of view is Samyang 35 mm F1.4. It has similar performance than the Sigma and has the best manual focus ring of the lenses I have used. It has also build quality and robustness comparable to a big Canon L.

Just received a Rokinon branded Samyang 35mm and very pleased with it. I did the Nikon mount and use a Nikon to EOS adapter with AF confirm chip. I got a great price on it and figured I'd rather do an adapter than get a Canon mount and try to afix an AF confirm chip to it. I've only shot a few shots so far and I'm impressed with sharpness at f/1.4...better than my Sigma 50 at f/1.4. The lens has an excellent build quality, reminds me of the 100L.

Note about manual focus: With a AF confirm chip you can shoot in aperture priority (which I almost always do anyway) or manual with floating ISO. Plus if you run Magic Lantern unified, you have the choice of focus peaking in live view (paints in focus areas) and also focus trapping in non-live view.

With focus trapping you half-press the shutter button then twist the focus ring while keeping the selected AF points in viewfinder on the desired target. As soon as it is in focus, it takes the shot. Very fast and effective when shooting in Av mode. Note it requires MFA to be set which of course is off by a mile due to thickness of the adapter. Hopefully the programable EXIF adapters have enough MFA programability to deal with it (which I would assume they do otherwise why put it on there?). I have a fixed EXIF adapter now but have a programmable version on the way and will post findings when it gets in...