Help with Sigma 30mm/1.4 + 350D

Started Jun 12, 2008 | Discussions
maxxjr
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Help with Sigma 30mm/1.4 + 350D
Jun 12, 2008

I just received a Sigma 30mm/1.4 back from Sigma after calibration with my 350D. After a few quick test shots @ f1.4 in failing evening light, I am still not happy with the lens. I plan on doing some more tests as I get a chance today, but a couple of questions as I proceed:

1. Is there anything that I really need to pay attention to when shooting at f1.4? I have read a number of comments about needing to learn to use the shallow DOF correctly--so some of what I may be seeing may be due to my inexperience with a fast lens. My only experience with a "fast lens" is with the Canon 50/1.8. I have not used the lens a lot, but it seemed to be okay in terms of focus/sharpness @ f1.8.

2. Can someone with the 350D + Sigma 30mm combo post a sample good image or two for me to set expectations?

Thanks,

M

Kreitmann
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 12, 2008

maxxjr wrote:

I just received a Sigma 30mm/1.4 back from Sigma after calibration
with my 350D. After a few quick test shots @ f1.4 in failing evening
light, I am still not happy with the lens. I plan on doing some more
tests as I get a chance today, but a couple of questions as I proceed:

It might be harsh, but you will never get perfect focus in low-light with this combo.

1. Is there anything that I really need to pay attention to when
shooting at f1.4? I have read a number of comments about needing to
learn to use the shallow DOF correctly--so some of what I may be
seeing may be due to my inexperience with a fast lens. My only
experience with a "fast lens" is with the Canon 50/1.8. I have not
used the lens a lot, but it seemed to be okay in terms of
focus/sharpness @ f1.8.

The AF of the 350D lacks the high precision focusing with fast lenses (faster than f/2.8) My 50mm 1.8 was often misfocusing with my 350D. When I upgraded to a 20D, which has a high precision center focus point, focus got much better.

The Sigma 30mm, well there where some problems with AF (search the forums for more info). I a still waiting for my 30mm to come back from calibration at the sigma service center. Focus was off, even with the 20D, even when stopped down to 2.8.

2. Can someone with the 350D + Sigma 30mm combo post a sample good
image or two for me to set expectations?

Stop down to 2.8 or 4, Take pictures of real live objects, (a brickwall or a fence at 45°) Use the Center focus point, inspect the results. f/1.4 is not a "normal" apertur. It took my some time to get used to it, to handle it. But, it is worth to learn.

Thanks,

M

Richard

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imqqmi
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 12, 2008

Ah yes I call this lens the sickma 30. If you can get hold of a healthy copy it's great.

I agree with kreitmann, the 350D is inherently inaccurate with this lens in low light. I've shot some with this camera and lens combo yesterday, some landscapes in a setting sun at f/8 and it did very well but have not tested it wide open yet in combination with 350D. Compared to my 40D which can focus with an accuracy of about 1/3 DOF. I estimate the 350D focuses within 2x dof which means that it sometimes front focus, back focus or be spot on. Hit the half press button a number of times and look at the focus ring flicking back and forth settling at a different spot almost each and every time. With the 40D it just sits there rock solid at the same spot.

What I usually did with the 350D is shooting 3 shots, refocusing each time. There's a 75% chance you nail the shot that way.

Make sure you test it on something that's about 3-4m away from the lens. A garden focusing on a plant pot for example, you'll get a good idea where it focuses with all the detailed foliage close by at different distances. Make sure you're level with the subject. If you point the lens down the dof will be at an angle with regard to the plant pot. This means that less of the dof falls behind the subject at ground level and more in the front. You're bound to asses the lens wrongly as front focusing.

See 'Don't Recompose' which is basically the same thing.
http://www.mhohner.de/recompose.php

The lens at 1.4 has a curved field of focus. In the corners the focus is bent towards you and diminishes when stopping down. So a focus test chart will mark this lens as front focus even though the center in perfectly in focus.

maxxjr wrote:

I just received a Sigma 30mm/1.4 back from Sigma after calibration
with my 350D. After a few quick test shots @ f1.4 in failing evening
light, I am still not happy with the lens. I plan on doing some more
tests as I get a chance today, but a couple of questions as I proceed:

1. Is there anything that I really need to pay attention to when
shooting at f1.4? I have read a number of comments about needing to
learn to use the shallow DOF correctly--so some of what I may be
seeing may be due to my inexperience with a fast lens. My only
experience with a "fast lens" is with the Canon 50/1.8. I have not
used the lens a lot, but it seemed to be okay in terms of
focus/sharpness @ f1.8.

2. Can someone with the 350D + Sigma 30mm combo post a sample good
image or two for me to set expectations?

Thanks,

M

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BadtzMaru
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to Kreitmann, Jun 12, 2008

Kreitmann wrote:

maxxjr wrote:

I just received a Sigma 30mm/1.4 back from Sigma after calibration
with my 350D. After a few quick test shots @ f1.4 in failing evening
light, I am still not happy with the lens. I plan on doing some more
tests as I get a chance today, but a couple of questions as I proceed:

It might be harsh, but you will never get perfect focus in low-light
with this combo.

I agree 100% with this. my 30D is better in really bad light and no AF assist, but I usually go MF before trying to get accurate AF. My 350D + the same sigma 30 Im using on my 30D would miss focus much more often, from experience with about 4 bodies now it seems the 350D focus was just not that great.

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maxxjr
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to BadtzMaru, Jun 12, 2008

The high-precision focus, or lack thereof is something that I haven't seen in a lot of for comparisons between the xxxD and xxD bodies. For example, I have read that the 40D will have better AF performance versus the XTi, but I can't remember seeing any further detail, such as better performance on lenses faster than f2.8. I always ready "better AF" as meaning faster or smarter electronics.

What other bodies have the "high-precision" focus point?

I was thinking about upgrading to a new body sometime in the next twelve months. Maybe I should look to do this sooner vs. later.

Would I see the same inconsistency if I went with the Canon 28/1.8 or Canon 50/1.4?

Should I just verify there are no major IQ issues and live with the AF inconsistency or MF until I get a new body?

Anyway, I appreciate the feedback. Learning something more about my kit today...

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BadtzMaru
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 12, 2008

maxxjr wrote:

The high-precision focus, or lack thereof is something that I haven't
seen in a lot of for comparisons between the xxxD and xxD bodies.
For example, I have read that the 40D will have better AF performance
versus the XTi, but I can't remember seeing any further detail, such
as better performance on lenses faster than f2.8. I always ready
"better AF" as meaning faster or smarter electronics.

Its a bit of both on thiss one. Well, all my lenses are 2.8 an faster so I take that back, but the difference to me was obvious

What other bodies have the "high-precision" focus point?

They all have at least 1, the 40D has more of them

I was thinking about upgrading to a new body sometime in the next
twelve months. Maybe I should look to do this sooner vs. later.

If you find it to be an issue, I agree. I didnt really know how much of a difference it was going to make me till I stopped getting oof shots with just about all my lenses

Would I see the same inconsistency if I went with the Canon 28/1.8 or
Canon 50/1.4?

Yes

Should I just verify there are no major IQ issues and live with the
AF inconsistency or MF until I get a new body?

Up to you

Anyway, I appreciate the feedback. Learning something more about my
kit today...

np!

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maxxjr
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to BadtzMaru, Jun 12, 2008

BadtzMaru wrote:

What other bodies have the "high-precision" focus point?

They all have at least 1, the 40D has more of them

So does the XT/350D have none, and even the XTi has added one "high-precision" focus point?

My limited testing was using only the center focus point on the XT/350D, and I would guess this would have been the "high-precision" focus point if it had one.

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BadtzMaru
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 12, 2008

So does the XT/350D have none, and even the XTi has added one
"high-precision" focus point?

no, like I said it has 1, the center AF point.

My limited testing was using only the center focus point on the
XT/350D, and I would guess this would have been the "high-precision"
focus point if it had one.

Yes.

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Chez Wimpy
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 12, 2008

maxxjr wrote:

2. Can someone with the 350D + Sigma 30mm combo post a sample good
image or two for me to set expectations?

I can't show you any examples, because I found out very quickly that it just isn't accurate enough to fuss with. I think I managed a couple with near hyperfocal and f1.4 via manual adjustment, but AF was a total crapshoot. If you want good focus sell the XT and get the XTi or the XSi (or 20D/30D/40D).

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Chez Wimpy
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to BadtzMaru, Jun 12, 2008

BadtzMaru wrote:

What other bodies have the "high-precision" focus point?

They all have at least 1, the 40D has more of them

cross sensors, yes... but still only one high-precision point (as usual, at the center)

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maxxjr
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to Chez Wimpy, Jun 13, 2008

Are the images below representative of what I can expect in terms of IQ on the Sigma 30/1.4?

Radio @ f4

Plant @ f2.5

Sports drink @ f2

Wall @ f1.4:

If this looks like a good copy, then my decision is between sitting on it with the XT until I get a newer body (and maybe trying to learn to use it even with focus issues on the XT), or send it back for now and get another later. If a bad copy, I'll just send it back and maybe try again later.

Thanks again!

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BadtzMaru
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Re: Help with Sigma 30mm/1.4 + 350D
In reply to maxxjr, Jun 13, 2008

Is there a filter on the lens by any chance? The edges of your images seem to be worse than Im used to seeing from my lens, and that wall shot is wacky.

The images http://www.flickr.com/photos/badtzmaruny1 there are pretty much ALL taken with the sigma and have exif info. They have mostly been post processed but a few are right out of the camera.

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imqqmi
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Comparison 350D vs 40D + sigma 30mm f/1.4 @ 1.4
In reply to imqqmi, Jun 16, 2008

I've done a quick comparison with a 350D and 40D focusing at near infinity. Although the 40D did better, it has still a bit of variation but much better than the 350D.

All shots handheld, 100% center crop, half press AF then took the picture, 5x repeated refocusing each time. The first shots are done by first focusing at something 1.5m away then focusing at the tower. Focus lock was confirmed each time. Shot in jpg with lowest setting of sharpening applied on each camera.

40D:

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350D:

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