sigma 50mm 1.4, very soft wider then 2.5

sarahparish91 · 02-06-2013, 12:29 AM

Hi, I have a Sigma 50mm 1.4, and a pentax k5, I usually stick to 2.5 or smaller as anything wider then that starts to get really soft, even if it's in focus, it looks like everything has glowing edges. Is this normal of the sigma lens, or is there something wrong with it? thanks,

SyncGuy · 02-06-2013, 12:47 AM

Just interested to know, when you mean the photo is in focus, are you meaning by using autofocus or manual focus?

Coz if you are using autofocus, it might just mean FF/BF issues. This would help the guys here out in troubleshooting your issues.

sarahparish91 · 02-06-2013, 12:54 AM

I usually use auto focus, but even when I use manual focus, the image will still have glowing edges regardless of whether or not it is in focus. If that makes sense, I will upload some sample images at different apertures in a minute

SyncGuy · 02-06-2013, 12:58 AM

Ouh..... Wait, don't upload just because i was asking..
I'm no expert when it comes to such detailed troubleshooting. Guess it's best to wait for those who are more experienced than me.

If it isn't FF/BF due to autofocus issues, i'm not too sure.

Bestzoom · 02-06-2013, 01:14 AM

The Sigma 50 is prompt to flare without the hood.

Did you use the lens hood?

**arv** · 02-06-2013, 01:34 AM

IMO you should better upload few examples. Sigma 50mm is famous as being sharp even wide open, and Sigma lenses are also famous for inconsistent autofocus, focus shift and being decentered.

A.

sarahparish91 · 02-06-2013, 01:57 AM

Here is a link to the photo on flickr, I've labeled the apertures below the photo. I cropped at 100% and tried to keep enough foreground and background in so you can see the focus is on the middle of the paperclip. I do use the lenshood, and these photos were taken on my back verandah, in the shade with the sun on the other side of the house. This fuzziness has always been there, I had read online that sometimes the photos are soft at a wider aperture, so I assumed it was that, but it's really bugging me I can't open it up further, so I thought I would check if it was normal or not.

Untitled | Flickr - Photo Sharing!

DSims · 02-06-2013, 02:44 AM

This is consistent with my experience with other (non-macro) Sigma lenses - they tend to be soft and/or have other significant image degradation within the first stop of wide-open.

It appears that the focus moves toward the front of the paper clip throughout this first stop, but it also appears that the focus point (wherever it is!) is still soft. A quick check of the images on Sigma 50mm F1.4 EX DG HSM Lens Sample Photos and Specifications also look to me like it can't deliver great images within the first 1-1.5 stops or so, similar to your observation.

Perhaps you do have a poorer copy - maybe some other Sigma owners can help you decide this. But I believe Sigma lenses generally cost less because they cost less to make, so I would expect you to encounter something similar again. However, as I said, those who own this specific lens can probably help you more.

However, to be fair, none of the Pentax 50s (except for the K or A 50/1.2) can deliver great images faster than f/2 either (I've owned all but one of the AF models, and a few MF ones). In fact, the DA*55 is the only 50ish AF K-mount lens I know of that can perform well near wide-open in the f/1.4 to f/1.8 range.

**kiwi_jono** · 02-06-2013, 02:44 AM

Looks like a classic case of Front Focus to me. You can see the area in front of the clip that is actually in focus.

To prove it, focus on the same scene (f1.4) with Live View (contrast focus setting) - I think you find it is then in focus.
I think you will need to tweak this in focus adjustment menu to fix it with phase focus.

sarahparish91 · 02-06-2013, 03:04 AM

What about the green glow on the out of focus areas of the paper clip at a wider aperture? I might try the same test in the am with a ruler, that might make it easier to see the focus point (should have thought of that earlier).

sTi · 02-06-2013, 03:14 AM

Originally posted by kiwi_jono

Looks like a classic case of Front Focus to me. You can see the area in front of the clip that is actually in focus.

To prove it, focus on the same scene (f1.4) with Live View (contrast focus setting) - I think you find it is then in focus.
I think you will need to tweak this in focus adjustment menu to fix it with phase focus.

The problem with the Sigma 50/1.4 seems to be that it (or at least several copies I've read about) show a pronounced focus shift (see here for explanation: What is Focus Shift? ) when stopping down. So whereas the focus will be in front at 1.4 (like in your sample IMO), it will be spot on by around 2.5 (after that the focus shift issue is normally no longer a problem, it usually occurs at the first one or two stops for fast lenses). So using an AF correction to get the focus right at 1.4 would mean that you will get back focus at smaller apertures. Not very useful IMO. Normally the LensROM inside the lens is supposed to correct the focus shift by telling the camera to use a different AF correction depending on the used f-stop. I don't know if Sigma uses this feature to communicate with the camera at all and thus whether it would be possible to correct this problem by sending it to Sigma for calibration.
My DA*55/1.4 does not show this behaviour at all, so it seems to be possible to avoid this focus shift issue with fast lenses.

sTi · 02-06-2013, 03:17 AM

Originally posted by sarahparish91

What about the green glow on the out of focus areas of the paper clip at a wider aperture? I might try the same test in the am with a ruler, that might make it easier to see the focus point (should have thought of that earlier).

This is called "bokeh fringing", see e.g. at the bottom of this page for an explanation and examples: Canon EF 100mm f/2.8 USM L IS macro (APS-C) - Review / Lab Test Report - Analysis

jpyykonen · 02-06-2013, 03:19 AM

Originally posted by sarahparish91

Hi, I have a Sigma 50mm 1.4, and a pentax k5, I usually stick to 2.5 or smaller as anything wider then that starts to get really soft, even if it's in focus, it looks like everything has glowing edges. Is this normal of the sigma lens, or is there something wrong with it? thanks,

I am no expert with this lens as I have not shot enough with it, but IMO the sharpness degrades towards the minimum focusing distance quite a lot, especially with the most wider apertures (seen best in the last picture; others were taken somewhere 1-3m from the subject). This is no macro lens after all. Here are few examples with the widest aperture. By clicking the thumbnail you should see the full size image. Those are without any particular post processing, just exported from Lightroom 4 with default settings. First two are with K-7, last one with K-5. Also these are not maybe the best examples for your style of shooting but examples nonetheless

And very beautiful photos btw in your flickr account! I can see you can use this lens as it should be used (I have lot to learn)!

sarahparish91 · 02-06-2013, 03:31 AM

sTi, thankyou for that!

jpyykonen, I cannot click on your thumbnails it comes up with a blank screen saying 'no access' ... And thankyou for your compliment, I am just in the process of uploading a bunch more photos

VisualDarkness · 02-06-2013, 03:31 AM

Sigma AF 50mm f/1.4 EX DG HSM (Canon) - APS-C Review / Test Report

Quote:

"The HSM ("Hyper-Sonic-Motor") AF is very fast and virtually silent. AF accuracy is a difficult topic for the Sigma. It seems to suffer from pronounced focus shifts when stopping down ("Residual spherical aberrations") which is probably the reason why many users report back- or front-focusing issues."

Yep, the focus is perfect at smaller apertures in your shots but quite front focused in the wide open one. Maybe calibrate it for wide open as it affects smaller apertures less?

It should be a really sharp lens and many recommends it over Pentax/Nikon/Canon 50/1.4 offerings due to being sharp straight from F1.4.

02-06-2013, 12:29 AM	#1
sarahparish91 Junior Member Join Date: Jul 2012 Location: Orange, NSW Photos: Albums Posts: 34	sigma 50mm 1.4, very soft wider then 2.5 Hi, I have a Sigma 50mm 1.4, and a pentax k5, I usually stick to 2.5 or smaller as anything wider then that starts to get really soft, even if it's in focus, it looks like everything has glowing edges. Is this normal of the sigma lens, or is there something wrong with it? thanks,

02-06-2013, 02:44 AM	#8
DSims Veteran Member Join Date: Sep 2009 Location: Southern California Photos: Gallery \| Albums Posts: 3,236	This is consistent with my experience with other (non-macro) Sigma lenses - they tend to be soft and/or have other significant image degradation within the first stop of wide-open. It appears that the focus moves toward the front of the paper clip throughout this first stop, but it also appears that the focus point (wherever it is!) is still soft. A quick check of the images on Sigma 50mm F1.4 EX DG HSM Lens Sample Photos and Specifications also look to me like it can't deliver great images within the first 1-1.5 stops or so, similar to your observation. Perhaps you do have a poorer copy - maybe some other Sigma owners can help you decide this. But I believe Sigma lenses generally cost less because they cost less to make, so I would expect you to encounter something similar again. However, as I said, those who own this specific lens can probably help you more. However, to be fair, none of the Pentax 50s (except for the K or A 50/1.2) can deliver great images faster than f/2 either (I've owned all but one of the AF models, and a few MF ones). In fact, the DA55 is the only 50ish AF K-mount lens I know of that can perform well near wide-open in the f/1.4 to f/1.8 range. Last edited by DSims; 02-06-2013 at 02:58 AM.*

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02-06-2013, 12:47 AM	#2
SyncGuy Veteran Member Join Date: Oct 2011 Posts: 821	Just interested to know, when you mean the photo is in focus, are you meaning by using autofocus or manual focus? Coz if you are using autofocus, it might just mean FF/BF issues. This would help the guys here out in troubleshooting your issues.

02-06-2013, 12:54 AM	#3
sarahparish91 Junior Member Join Date: Jul 2012 Location: Orange, NSW Photos: Albums Posts: 34 Original Poster	I usually use auto focus, but even when I use manual focus, the image will still have glowing edges regardless of whether or not it is in focus. If that makes sense, I will upload some sample images at different apertures in a minute

02-06-2013, 12:58 AM	#4
SyncGuy Veteran Member Join Date: Oct 2011 Posts: 821	Ouh..... Wait, don't upload just because i was asking.. I'm no expert when it comes to such detailed troubleshooting. Guess it's best to wait for those who are more experienced than me. If it isn't FF/BF due to autofocus issues, i'm not too sure.

02-06-2013, 01:14 AM	#5
Bestzoom Senior Member Join Date: Aug 2011 Location: Sydney Photos: Albums Posts: 232	The Sigma 50 is prompt to flare without the hood. Did you use the lens hood?

02-06-2013, 01:34 AM	#6
arv Loyal Site Supporter Join Date: Aug 2010 Photos: Albums Posts: 413	IMO you should better upload few examples. Sigma 50mm is famous as being sharp even wide open, and Sigma lenses are also famous for inconsistent autofocus, focus shift and being decentered. A.

02-06-2013, 01:57 AM	#7
sarahparish91 Junior Member Join Date: Jul 2012 Location: Orange, NSW Photos: Albums Posts: 34 Original Poster	Here is a link to the photo on flickr, I've labeled the apertures below the photo. I cropped at 100% and tried to keep enough foreground and background in so you can see the focus is on the middle of the paperclip. I do use the lenshood, and these photos were taken on my back verandah, in the shade with the sun on the other side of the house. This fuzziness has always been there, I had read online that sometimes the photos are soft at a wider aperture, so I assumed it was that, but it's really bugging me I can't open it up further, so I thought I would check if it was normal or not. Untitled \| Flickr - Photo Sharing!

02-06-2013, 02:44 AM	#9
kiwi_jono Loyal Site Supporter Join Date: Dec 2009 Location: Christchurch, New Zealand Photos: Gallery \| Albums Posts: 2,437	Looks like a classic case of Front Focus to me. You can see the area in front of the clip that is actually in focus. To prove it, focus on the same scene (f1.4) with Live View (contrast focus setting) - I think you find it is then in focus. I think you will need to tweak this in focus adjustment menu to fix it with phase focus.

02-06-2013, 03:04 AM	#10
sarahparish91 Junior Member Join Date: Jul 2012 Location: Orange, NSW Photos: Albums Posts: 34 Original Poster	What about the green glow on the out of focus areas of the paper clip at a wider aperture? I might try the same test in the am with a ruler, that might make it easier to see the focus point (should have thought of that earlier).

02-06-2013, 03:14 AM	#11
sTi Forum Member Join Date: Feb 2011 Posts: 98	Originally posted by kiwi_jono Looks like a classic case of Front Focus to me. You can see the area in front of the clip that is actually in focus. To prove it, focus on the same scene (f1.4) with Live View (contrast focus setting) - I think you find it is then in focus. I think you will need to tweak this in focus adjustment menu to fix it with phase focus. The problem with the Sigma 50/1.4 seems to be that it (or at least several copies I've read about) show a pronounced focus shift (see here for explanation: What is Focus Shift? ) when stopping down. So whereas the focus will be in front at 1.4 (like in your sample IMO), it will be spot on by around 2.5 (after that the focus shift issue is normally no longer a problem, it usually occurs at the first one or two stops for fast lenses). So using an AF correction to get the focus right at 1.4 would mean that you will get back focus at smaller apertures. Not very useful IMO. Normally the LensROM inside the lens is supposed to correct the focus shift by telling the camera to use a different AF correction depending on the used f-stop. I don't know if Sigma uses this feature to communicate with the camera at all and thus whether it would be possible to correct this problem by sending it to Sigma for calibration. My DA*55/1.4 does not show this behaviour at all, so it seems to be possible to avoid this focus shift issue with fast lenses.

02-06-2013, 03:17 AM	#12
sTi Forum Member Join Date: Feb 2011 Posts: 98	Originally posted by sarahparish91 What about the green glow on the out of focus areas of the paper clip at a wider aperture? I might try the same test in the am with a ruler, that might make it easier to see the focus point (should have thought of that earlier). This is called "bokeh fringing", see e.g. at the bottom of this page for an explanation and examples: Canon EF 100mm f/2.8 USM L IS macro (APS-C) - Review / Lab Test Report - Analysis

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02-06-2013, 03:19 AM	#13
jpyykonen Senior Member Join Date: Jan 2007 Location: Tampere, Finland Posts: 191	Originally posted by sarahparish91 Hi, I have a Sigma 50mm 1.4, and a pentax k5, I usually stick to 2.5 or smaller as anything wider then that starts to get really soft, even if it's in focus, it looks like everything has glowing edges. Is this normal of the sigma lens, or is there something wrong with it? thanks, I am no expert with this lens as I have not shot enough with it, but IMO the sharpness degrades towards the minimum focusing distance quite a lot, especially with the most wider apertures (seen best in the last picture; others were taken somewhere 1-3m from the subject). This is no macro lens after all. Here are few examples with the widest aperture. By clicking the thumbnail you should see the full size image. Those are without any particular post processing, just exported from Lightroom 4 with default settings. First two are with K-7, last one with K-5. Also these are not maybe the best examples for your style of shooting but examples nonetheless And very beautiful photos btw in your flickr account! I can see you can use this lens as it should be used (I have lot to learn)!

02-06-2013, 03:31 AM	#14
sarahparish91 Junior Member Join Date: Jul 2012 Location: Orange, NSW Photos: Albums Posts: 34 Original Poster	sTi, thankyou for that! jpyykonen, I cannot click on your thumbnails it comes up with a blank screen saying 'no access' ... And thankyou for your compliment, I am just in the process of uploading a bunch more photos

02-06-2013, 03:31 AM	#15
VisualDarkness Veteran Member Join Date: Nov 2011 Location: Uppsala, Sweden Photos: Gallery Posts: 4,439	Sigma AF 50mm f/1.4 EX DG HSM (Canon) - APS-C Review / Test Report Quote: "The HSM ("Hyper-Sonic-Motor") AF is very fast and virtually silent. AF accuracy is a difficult topic for the Sigma. It seems to suffer from pronounced focus shifts when stopping down ("Residual spherical aberrations") which is probably the reason why many users report back- or front-focusing issues." Yep, the focus is perfect at smaller apertures in your shots but quite front focused in the wide open one. Maybe calibrate it for wide open as it affects smaller apertures less? It should be a really sharp lens and many recommends it over Pentax/Nikon/Canon 50/1.4 offerings due to being sharp straight from F1.4.