Sigma 50mm 1.4 - Front Focus or Pixel Peeping?

[short_wave]

Just got my lens in from Adorama yesterday and I am contemplating sending it in for calibration. What do you guys think?

Placed on tripod/ 45 degree angle/ constant light source (daylight bulb) / Aperture Priority

f/1.4



f/2



f3.2 (Sharp)

[Snydremark]

Looks like front focus; but shooting at an angled target like that can easily screw up your AF system. Try with a better target, such as the Spyder LensCal target or TeamSpeed's Focus Genie chart.

This way, you are actually AF'ing on a specific plane (the vertical) and then have the angled bit to check where your focus hit. Shooting the angled target like you have here, the camera will focus "somewhere" within the depth of coverage of your AF spot. And since the AF spot functional area is slightly larger than the boxes you see in the viewfinder, this can lead to misdiagnosis of front or back focus issues.

[booja]

8-10mm in front

[davidc502]

Do the battery test....

Just realize no lens is perfect. The results above in no way will tell you what to expect in real life. They don't discount it either.

[short_wave]

Originally Posted by davidc502

Do the battery test....

Just realize no lens is perfect. The results above in no way will tell you what to expect in real life. They don't discount it either.

Understood.

I just want to know if this is the front focus that other Sigma owners are experiencing. As booja mentioned, it is 8-10mm in front. Is this acceptable?

Here is the battery test I did last night (f/1.4)..


And I shot I took that earlier that evening (f/1.4)...

[sharrowm]

Originally Posted by short_wave

Understood.

I just want to know if this is the front focus that other Sigma owners are experiencing. As booja mentioned, it is 8-10mm in front. Is this acceptable?

Here is the battery test I did last night (f/1.4)..


And I shot I took that earlier that evening (f/1.4)...

Looks like front focus to me. I just purchased the same lens with the same problems. My post is here:

http://photography-on-the.net/forum/....php?t=1144894

My lens seems to be about the same as yours from a distance of ~2ft, but at ~4ft it seems to be pretty close to dead-on. I am curios to know if your lens reacts the same way.

[short_wave]

Originally Posted by sharrowm

Looks like front focus to me. I just purchased the same lens with the same problems. My post is here:

http://photography-on-the.net/forum/....php?t=1144894

My lens seems to be about the same as yours from a distance of ~2ft, but at ~4ft it seems to be pretty close to dead-on. I am curios to know if your lens reacts the same way.

Yes!

At 2ft at f/1.4, the image is pretty much useless. Once I step back to about 4-6ft (still at f/1.4) the image looks great! This is what's throwing me off and forcing this over-analyzation.

I've checked out your thread and it seems like you are getting the same responses. Didn't want to hi-jack your thread! What did you end up doing?

[sharrowm]

Originally Posted by short_wave

Yes!

At 2ft at f/1.4, the image is pretty much useless. Once I step back to about 4-6ft (still at f/1.4) the image looks great! This is what's throwing me off and forcing this over-analyzation.

I've checked out your thread and it seems like you are getting the same responses. Didn't want to hi-jack your thread! What did you end up doing?

I'm still on the fence, but leaning towards keeping it as-is for a while and see how often the close-focus/front-focus issue comes into play with the way I shoot. I have 4 years to send it in under warranty if need be. But shots like this really make me want to forgive its AF issues (f1.4 at about 4ft focus on the "nose" ):

[booja]

i sent mine in... mine needed +10 or so

came back and it seemed the same... i was like ok they did nothing.

on my 7d that i had and on my 5dc its spot on. i guess its my 5d2. try another camera... if you or your buddies have another one. but knowing sigma its probably the lens. if thats the case send it in if you have warranty. they have a good warranty so why not use it. if you return it for another one you have a possibility of getting another bad one

[short_wave]

Thanks booja (love your work btw!)

I wish I had another camera to try this out on. I have friend that has a 5d2 but he is out of town on an assignment.

I'm thinking about sending it to Sigma..but I'm also thinking about returning it and getting the Canon version...not really sure. I have a senior shoot next month and so I need to make a decision this week on what I'm going to do.

[short_wave]

I know what you mean.

Truth be told I will more than likely stop down the lens but I do want the ability to use 1.4. I'm normally not that close when shooting 50mm just seems like I'm being limited.

[ejenner]

Originally Posted by short_wave

I know what you mean.

Truth be told I will more than likely stop down the lens but I do want the ability to use 1.4. I'm normally not that close when shooting 50mm just seems like I'm being limited.

my 2-c..

Without a MF adjust camera, I honestly think this is about as good as you can expect. You might get the Canon version to be closer, but really for a Sigma prime on a Canon I think this is really, really close. If the focusing is consistent I would consider it a good copy.

Also, I would not send it to sigma - honestly it might actually come back farther out than that and you'll be in for a protracted back-and-forth.

Maybe just be aware that you might have to focus just a little behind where you actually want focus, but in practice I always take several shots at f1.4 because slight movements in camera or subject position will change exactly where the focus falls. In the dog shot for instance, even with a perfect lens it is hard to get the focus spot-on where you want it and requires a bit of a burst + some luck (maybe depending on how picky you are).

Maybe I'm biased because I'd be delighted if my Sigma 85 1.4 was as close to this on my T1i instead of being a good inch or more front focusing.

[short_wave]

Originally Posted by ejenner

my 2-c..

Without a MF adjust camera, I honestly think this is about as good as you can expect. You might get the Canon version to be closer, but really for a Sigma prime on a Canon I think this is really, really close. If the focusing is consistent I would consider it a good copy.

Also, I would not send it to sigma - honestly it might actually come back farther out than that and you'll be in for a protracted back-and-forth.

Maybe just be aware that you might have to focus just a little behind where you actually want focus, but in practice I always take several shots at f1.4 because slight movements in camera or subject position will change exactly where the focus falls. In the dog shot for instance, even with a perfect lens it is hard to get the focus spot-on where you want it and requires a bit of a burst + some luck (maybe depending on how picky you are).

Maybe I'm biased because I'd be delighted if my Sigma 85 1.4 was as close to this on my T1i instead of being a good inch or more front focusing.

I see what you are saying. I've only been shooting for a couple of years, so please forgive me for sounding like a n00b, but is it common to compensate for a lens' inability to properly auto-focus? It seems counter-intuitive to apply a technique like that. I do know that lenses have their quirks but I'm just not so sure if I want to compensate like that for a lens that I paid a good amount of money for. Especially for something as fundamental as AF.

Again, please forgive me if I come off sounding sarcastic or whatnot, I'm really not trying to be! I just want to know.

[Jasper Ash]

So when you guys say "front focus", are you talking about the way the lens miss focuses on an area other than the focus target area? Not so much that its a soft lens, but rather the AF is not accurate and needs calibrated?

[sharrowm]

Originally Posted by Jasper Ash

So when you guys say "front focus", are you talking about the way the lens miss focuses on an area other than the focus target area? Not so much that its a soft lens, but rather the AF is not accurate and needs calibrated?

Exactly. The lens focuses in front of the subject. It has nothing to do with the sharpness of the lens. Just the accuracy of the af.