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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 07 Jun 2011 (Tuesday) 16:41
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Complains for Sig 30mm

 
cfvisuals
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Jun 07, 2011 16:41 |  #1

This is what I realized, occasionally, the focusing of my Sigma 30mm F1.4 fails me. Especially under low-light environment, it is slow and inaccurate. Well it's not terribly slow and inaccurate, but it does happen at times. It isn't front/back focusing, i tested it with the focusing chart. For other times the focusing isn't failing me, the images are crystal sharp, very sharp.

So I wonder do you guys have similar problems, or it's just me?
I have thought about switch it to 85mm 1.8, cause I am still struggling with the FL decision. I am not completely sure if i need the width of the 30mm.
is 85mm 1.8 USM focusing way faster and more accurate?

(EDIT: under enough ambient light, it doesn't struggle much)


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Sirrith
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Jun 07, 2011 16:43 |  #2

In very low light the sigma struggles, but other than that, mine focuses just fine.
I'm not sure if you're saying yours only fails you in low light, or that it happens in good light too, just not as often?
As for the 85 1.8, I'd never switch my 30mm for one, but I would definitely consider getting it as well as my 30 1.4, it would make a good complement.


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sbattey
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Jun 07, 2011 17:41 |  #3
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Any lens can miss focus, maybe you're being overly critical because you know its a sigma?


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cfvisuals
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Jun 07, 2011 18:04 |  #4

sbattey wrote in post #12553972 (external link)
Any lens can miss focus, maybe you're being overly critical because you know its a sigma?

That could be the case. You are right, it could be a mental problem with myself.


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shooter ­ mcgavin
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Jun 07, 2011 18:17 |  #5

the focus on the 85 f/1.8 is much faster and more accurate, but considering the focal-length difference, they aren't comparable. Looking at the other lenses you have, the 85 may be a good choice if your 70-200 is the f/4 version, since it will give you a bit more reach for low-light situations, while your 17-50 can pick up the wide and mid range.




  
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asamimasa
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Jun 07, 2011 18:20 |  #6

Lots of lenses hunt/don't lock focus in darker situations. Sigma 30 may be one of them (was in my case + Teddy in UCSDPC). Although in some cases it could be body, but I'm not too sure how that works- the 1D series isn't great at locking focus in dark.The 85 1.8 focuses a lot faster, but that's partially due to its focal length.
Usually, when I want to see if it really is my lens that's having an issue or me selecting a bad place to focus on, I'll try focusing on something really contrasty. Say I want to take a low-light shot of someone and I'm having a hard time locking onto their face. I'd attempt to focus on the hairline or something, and if it still doesn't work, I'll bust out some fill light like a phone so I can catch focus.


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cfvisuals
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Jun 07, 2011 18:20 |  #7

shooter mcgavin wrote in post #12554139 (external link)
the focus on the 85 f/1.8 is much faster and more accurate, but considering the focal-length difference, they aren't comparable. Looking at the other lenses you have, the 85 may be a good choice if your 70-200 is the f/4 version, since it will give you a bit more reach for low-light situations, while your 17-50 can pick up the wide and mid range.

Right that's what I was thinking, it's truely can't compare. My struggle is really just deciding whether if i need the 30mm indoor. If i don't, I will go for the reach.


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shooter ­ mcgavin
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Jun 07, 2011 18:24 |  #8

Tape your 70-200 to around 85mm and walk around with it for a bit, both indoors and outdoors. See if it's a length that would be useful to you. If not, maybe you don't need either and could put the funds towards lights :)




  
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cfvisuals
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Jun 07, 2011 18:24 |  #9

asamimasa wrote in post #12554151 (external link)
Lots of lenses hunt/don't lock focus in darker situations. Sigma 30 may be one of them (was in my case + Teddy in UCSDPC). Although in some cases it could be body, but I'm not too sure how that works- the 1D series isn't great at locking focus in dark.The 85 1.8 focuses a lot faster, but that's partially due to its focal length.
Usually, when I want to see if it really is my lens that's having an issue or me selecting a bad place to focus on, I'll try focusing on something really contrasty. Say I want to take a low-light shot of someone and I'm having a hard time locking onto their face. I'd attempt to focus on the hairline or something, and if it still doesn't work, I'll bust out some fill light like a phone so I can catch focus.

like one hand with an iphone with flashlight app on, other hand with your camera !


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HansSteinert
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Jun 07, 2011 18:27 |  #10

What aperture are you shooting at when your focus is inconsistent? If you're shooting at under f2, you could be missing focus by slightly moving the camera forward or backward with your hands in between the time you AF and the time you take the picture. The DOF is so thin that something as small as that will make it soft.




  
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cfvisuals
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Jun 07, 2011 18:30 |  #11

HansSteinert wrote in post #12554174 (external link)
What aperture are you shooting at when your focus is inconsistent? If you're shooting at under f2, you could be missing focus by slightly moving the camera forward or backward with your hands in between the time you AF and the time you take the picture. The DOF is so thin that something as small as that will make it soft.

I noticed that actually, I had questioned myself once about that. It's more like my subject is not standing still while my focus is not fast enough to keep up with his/her movement. I usually try to shoot at f/2, I try to avoid 1.4 for portraits. It's too thin. And thanks, I will pay extra attention to that in the future.


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shaftmaster
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Jun 07, 2011 18:44 |  #12

I did a very non-scientific low light focus test a year or two ago and compared several lenses (35 f/2, 50 f/1.8 mk1, 50 f/1.4, 50 f/2.5 macro, and 85 f/1.8) on two bodies (XTi/400D and 40D) using center AF point only. For the test, I focused each lens and body combination on a low contrast spot in poor light. All of the lenses were able to achieve focus on the same spot except for the 50mm f/2.5 macro and the 85 f/1.8. I don't think this implies that the 85 f/1.8 is a bad lens, but it shows that in poor light any lens can miss focus or not achieve focus at all. I had always assumed that a ring USM lens would have less trouble focusing in low light but in my test, the non-USM lenses did better. Maybe that was due to the non-USM lenses having slower AF?


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artyH
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Jun 07, 2011 19:18 |  #13

My 85f1.8, Canon 35f2 and Canon 50f1.4 will all hit focus accurately in low light on my T2i and XS. The shorter the focal length, the easier it is to use the lens in low light, because you can use it at slower shutter speeds.
I generally like the 35f2 for low light, but the 50f1.4 works well too. I can use the 85, but it requires a much larger space and higher shutter speeds, like 1/125 or faster. I can get decent shots with the 85 at 1/100, but I can do better with the 35f2, like 1/50 or 1/60 or even slower.




  
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ekinnyc
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Jun 08, 2011 10:39 |  #14

i love my siggy 30... but it definitely hunts a bit in low light. not nearly as bad as the canon 50 1.8 though


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xanavi
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Jun 08, 2011 14:22 |  #15

I heard there are good and bad batches of 30mm 1.4. You may have bought the bad patch. Try going through warranty.




  
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Complains for Sig 30mm
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