I need help with my new Sigma 35m 1.4

JTB-DC

Hi all,

Hoping you could weigh in on the following. I purchased the new Sigma 35 1.4. I will start by saying it is amazing when it works. But I seem to be having some focusing issues. I "tested" it on both my D600 and D300s. By test, I mean I have been shooting pics, mostly around the house, indoors and in low light. Took it outside a few times as well, which fairs better, but two issues have arisen.

1. In low light, it has a really hard time grabbing hold of the intended subject. The D300s has a harder time than the D600, but both have issues. I know, I have read some people have run into this issue, but this one REALLY seems to have a hard time under not very "low light" conditions.

2. The lens grabs hold of the subject and either back focuses or front focuses. Neither seem to be occurring more-so than the other. But such inconsistency renders AF fine-tune worthless right? Again, this happens on the D300s much more than the D600.

Again, when I say "low light", I am talking about a normal 18x15 white-walled room with one lamp (60w bulb) on and a 42 inch tv on that is also pretty bright. Point being, the conditions are not all that dark even.

I tested my Nikon 24-120 under the same conditions on both cameras and it seemed to have no problem grabbing hold of many of the subjects the Sigma can't grab.

So I inquired with Sigma and explained the two issues and the response was the following:

"Unfortunately we cannot improve the focusing in low light as this is related to the camera and the design of the lens. But we will be happy to calibrate the lens for you if you send it in to us." :scratch

Do any of you find this a little odd? Might be I am missing the boat here (and posting so you guys can tell me if I am), but buying 1.4 in my opinion has two purposes.

1. going nuts with your artistic expression DoF-wise
2. low light photography (which btw, on the Sigma website it says this lens is "ideal" for low light)

Second, blaming it on my camera? Sure maybe it needs calibration, but I specifically explained that I have tested the Sigma using two cameras and another Nikon lens for comparison, so I am thinking chances are that isn't it.

I guess I'm wondering if any of you have experience with Sigma and a feeling on whether the calibration will work (or alternatively if it doesn't they will do whatever needs to be done until I get a good copy) or if I should just send it back to where I purchased it in exchange for a new one and chance another off-the shelf copy will be better? Maybe I am being cynical, but their email didn't fill me with confidence.

Any opinions would be helpful.

ziggy53

If by "Sigma 35 1.4" you mean the Sigma 35mm F1.4 DG HSM, it should be capable of accurate, or at least consistent, focus.

It does concern me that you think the light from "one lamp (60w bulb) on and a 42 inch tv" is "not all that dark even", because that sounds pretty dark to me. You also don't mention the subject matter or AF mode and AF settings, all of which can have a bearing on AF accuracy and AF speed.

Autofocus systems, even on brand new camera bodies, are still less capable than the image sensor on most cameras, in terms of light sensitivity. If you give the AF sensor a relatively low contrast and rounded subject, like a human head, for instance, it can be "very" difficult for any camera to find and lock focus in low light.

In those lighting conditions I recommend using One-Shot AF mode and only the center AF dot. Add a Nikon SU-800 Wireless Speedlight Commander for its AF Assist lamp, and you have a pretty good chance of fast and accurate AF in almost any low lighting condition.

JTB-DC

ziggy53 wrote: »

If by "Sigma 35 1.4" you mean the Sigma 35mm F1.4 DG HSM, it should be capable of accurate, or at least consistent, focus.

It does concern me that you think the light from "one lamp (60w bulb) on and a 42 inch tv" is "not all that dark even", because that sounds pretty dark to me. You also don't mention the subject matter or AF mode and AF settings, all of which can have a bearing on AF accuracy and AF speed.

Autofocus systems, even on brand new camera bodies, are still less capable than the image sensor on most cameras, in terms of light sensitivity. If you give the AF sensor a relatively low contrast and rounded subject, like a human head, for instance, it can be "very" difficult for any camera to find and lock focus in low light.

In those lighting conditions I recommend using One-Shot AF mode and only the center AF dot. Add a Nikon SU-800 Wireless Speedlight Commander for its AF Assist lamp, and you have a pretty good chance of fast and accurate AF in almost any low lighting condition.

Hi Ziggy!

Thanks for your reply, let me clarify a few things, as you have some good points.

First, yes I am referring to the new Sigma 35mm 1.4 DG HSM. Sorry about that.

Regarding the light, perhaps I didn't describe the lighting conditions well, or should have just left it at "relatively low light" instead of trying to describe it. Let's just say between the lamp, the tv, the white walls, the street lights coming in through large windows that we have no curtains on, etc..I didn't think it was so dimly lit that the cameras should have a problem. Also, when trying my Nikon 24-120 F4 in the same conditions with both cameras as well, neither camera with the 24-120 F4 mounted had even half as hard a time locking focus on many of the same subjects.

Subjects: everything and everything in a typical living room. Just trying to see outcomes for as many possible situations as I can. As you state, I expect low contrast less defined objects to be harder on the AF system, but I go back to comparing how the 24-120 F4 performs so much better on same objects in the same light.

Also, I am shooting single shots at AF-S with the AF dot in the center as you suggest.

I will go home and play some more tonight, but the lens didn't seem up to snuff and the response from Sigma was less than encouraging and wondered folks' past experience or thoughts.

Thanks again!