Sigma 30mm f1.4

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ecniv

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Hi,

Bought a sigma 30mm f1.4

But the focus doesn't appear to be in the middle (even when camera is selected in the middle). To get it near right I had to fine to +10.

Is the right for this lens?
Is there anywhere to get the lens calibrated?
Could my camera need adjusting?

I'm in the Birmingham area and would prefer that I drop the lens in manually for the person to calibrate rather than mail it.

Thanks in advance
 
it doesn't sound right. If its new get a replacement from the reatiler, if not return to sigma for calibration
 
I had one of these on an Alpha. It highlighted the general back-focus problem the camera had. My 2 kit lenses had such comparatively large depth of field I hadn't noticed before. Basically I fixed the back focus in the body to match the Sigma and then tried everything out to be sure I hadn't broken the kit lenses and all was well. I'm only telling you this in case this is the same issue you're having.
 
What focusing distance did you test it at? If it was less than about 1m, that might be the problem - it could be fine at more normal distances. Just a thought.
 
I spent hours today trying to prove that one of my lenses is faulty. Sadly it isn't, it's just my technique. :help: :)
 
Wide Sigmas have need microfocus adj for use at large apertures in my experience. I use a 500mm f1.4 and have set mf in camera menu.
 
Hi mate,

just curious to know.

Did you notice the focus problems while using the flash or when not using the flash.

Can you able to post the sample pictures..?
 
phototuition said:
Wide Sigmas have need microfocus adj for use at large apertures in my experience. I use a 500mm f1.4 and have set mf in camera menu.
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thats a big front element.

A properly calibrated modern lens shouldn't need a focus adjust of +-10 in any circumstance
 
Good one.

If you use any flash with Flash assist mode ...with third party lenses, Nikon D300 used to behave bit odd in focusing. That's the reason I've asked before.

Also since you said it is seems ok now, May be you should check with another camera if you have one or you can borrow if any, just to reconfirm ( Looks like the settings may be the issue)
 
I absolutely LOVE this lens, the only drawback to going full frame was having to sell it.
 
Yup, it's a great lens and my only complaint (other than it's APS-C) is that the HSM feels a bit gritty to me but I don't think it's a fault as I've tried others and they felt the same.
 
Flash In The Pan said:
At what aperture are these problems manifesting themselves - f/1.4. by any chance?
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This is a good question. Remember that most digital SLR viewfinders don't display true depth of field with lenses faster than f2.8.

Using liveview should be OK though.
 
For me an important thing to remember is that if there's a difference between what I saw through the viewfinder and what I see on the computer screen there's probably an explanation such as subject movement, hand shake or a slight movement of my body as the shutter fires. These are hard things to control and have an effect when taking shots with minimal DoF.

I recently took about 60 shots at a dimly lit party and I just had to accept that shooting at f1.4 and at ISO 400 to 3200 I was pushing the capabilities of the lens, the cameras autofocus system and my own physical capabilities to the absolute limit.
 
manualfocus-g said:
This is a good question. Remember that most digital SLR viewfinders don't display true depth of field with lenses faster than f2.8.

Using liveview should be OK though.
Click to expand...

I'm not sure I see the relevance. Of course any focusing errors are more apparent at f/1.4, where depth of field is very shallow indeed. What you see in the viewfinder doesn't affect the image.

The problem is much more likely to be testing at too close distance, which looks to be the case here. Not only are you at the extreme end of the focusing range, but the focusing mechanism needs a much greater degree of accuracy at that end. Macros are specifically designed to cope with this, hence their much larger sizes and chunky focusing mechs. When you then add the very shallow DoF you get at f/1.4, demanding even more precision from both the lens and the user, then that's when problems creep in.

Good comment from WW though. The reality of using a lens like this is that almost always the limiting factor is the user, or should I say the shooting situation. Most of the time, you just can't nail the focus that accurately and if it's out, it's because the subject moved position, or you moved, or you used focus-recompose without thinking, or you stuck the focus point on the wrong thing. And that's completely ignoring the most likely culrpit of all - camera shake. The fact that the AF system might be 2mm back focused will probably be the least of your worries.
 
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manualfocus-g said:
The relevance is obvious isn't it? If you can't tell whether the correct part of the image is in focus in the viewfinder, how would you expect to get accurately focused images?
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Ah right, I'm with you now. Yes, you usually want a different focusing screen for manual focusing low f/number lenses. That makes it easier, because they show the effect of shallow depth of field more accurately, though that doesn't stop you focusing accurately without one.

But more significantly, this thread is about auto-focus accuracy, which has nothing to do with the viewfinder.
 
manualfocus-g said:
This is a good question. Remember that most digital SLR viewfinders don't display true depth of field with lenses faster than f2.8.

Using liveview should be OK though.
Click to expand...


What I was actually getting at (as mentioned by Richard, above) is that people buy these lenses and shoot with them wide open and the think their example is faulty because everything appears oof, when in fact what the real problem is is that they don't appreciate just how narrow the dof is at f/1.4.

I'd reckon that 99% of the "faulty" versions of this lens that people have posted about online are really perfectly fine, the real cause of the problem is operator error....
 
Hi


Yeah probably me (puts hand up and looks at feet) operator error...

Anyways, here is a link to the flickr site and some pics... what do you think (these were taken with the tweak in place, have since removed the fine tune).

Flickr Set for 30mm
 
they look fine at that size to me. I also used to have this lens on my crop and it was soooo nice. gutted i couldn't keep it when i went to full frame.
 
HoppyUK said:
But more significantly, this thread is about auto-focus accuracy, which has nothing to do with the viewfinder.
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I think this is a bit off topic now as clearly the issue has now been narrowed to a misunderstanding of the razor thin depth of field at f1.4.

However, I still think my comment is relevant to auto focusing. A high precision screen is not just useful for manual focusing, it allows you to see what is really in focus in the viewfinder (which I presume most people do, auto or manual focus aside). At f1.4 or faster this is critical, as that shallow depth of field can be a killer if you are relying on the camera getting it right just using AF.

If you haven't already tried one, give it a go on the 5D II, the difference is incredible when shooting indoors at f1.2-f1.4.
 
manualfocus-g said:
I think this is a bit off topic now as clearly the issue has now been narrowed to a misunderstanding of the razor thin depth of field at f1.4.

However, I still think my comment is relevant to auto focusing. A high precision screen is not just useful for manual focusing, it allows you to see what is really in focus in the viewfinder (which I presume most people do, auto or manual focus aside). At f1.4 or faster this is critical, as that shallow depth of field can be a killer if you are relying on the camera getting it right just using AF.

If you haven't already tried one, give it a go on the 5D II, the difference is incredible when shooting indoors at f1.2-f1.4.
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It's an interesting comment for sure, and using the right screen for low f/number lenses certainly shows the shallow DoF better in the viewfinder.

However, it implies that you cannot manually focus lenses like that without one of these screens, when of course you can - it just makes it easier. And further, there's no way that I can focus more accurately in this way than I can with AF, and it also takes very much longer. AF systems are at their best with low f/number lenses, independent of the type of focusing screen.
 
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HoppyUK said:
It's an interesting comment for sure, and using the right screen for low f/number lenses certainly shows the shallow DoF better in the viewfinder.

However, it implies that you cannot manually focus lenses like that without one of these screens, when of course you can - it just makes it easier. And further, there's no way that I can focus more accurately in this way than I can with AF, and it also takes very much longer. AF systems are at their best with low f/number lenses, independent of the type of focusing screen.
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Hehe, totally understand what you are saying, but still if you can't see the true depth of field and focus point in the viewfinder, how do you know the AF has picked the correct, small part of the focus plane? ;)

From Canon (talking about the EE-S focus screen):

"It gives more confidence in the accuracy of autofocus and is especially recommended for manual focus. Even in low light, the reduction in viewfinder brightness is offset by the ease of getting the focus point just right."

Anyway, that's enough from me :D
 
manualfocus-g said:
Hehe, totally understand what you are saying, but still if you can't see the true depth of field and focus point in the viewfinder, how do you know the AF has picked the correct, small part of the focus plane? ;)

From Canon (talking about the EE-S focus screen):

"It gives more confidence in the accuracy of autofocus and is especially recommended for manual focus. Even in low light, the reduction in viewfinder brightness is offset by the ease of getting the focus point just right."

Anyway, that's enough from me :D
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:)

And me :D
 
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