Sigma 50mm f/2.8 EX DG Macro infinity focus issue

Bronmar · 11-29-2012, 06:38 PM

Has anyone had an issue with infinity focus using Sigma 50mm f/2.8 EX DG Macro.
It's a perfect auto/manual focus in macro and short distances but it's always blurry for the subject further away from the lens. Even you can clearly see that it's in a perfect focus using auto/manual focusing (viewfinder or LV). The camera used is Pentax k r.

stevebrot · 11-29-2012, 08:56 PM

Hi! Welcome to Pentax Forums!

I own a copy of that lens and have not had any focus issues at any point in its focus range.

So...you get fuzzy photos even when the LCD image in live view is sharp and only when the subject is at infinity? The final image should be at least as sharp as the LCD. Be aware that pixel peeping at the captured image of a distant subject will be intrinsically disappointing when compared to nearer subjects due to haze and intervening atmospheric variations. This is true with even the best lenses.

Steve

Bronmar · 11-30-2012, 08:47 AM

Originally posted by stevebrot

Hi! Welcome to Pentax Forums!

I own a copy of that lens and have not had any focus issues at any point in its focus range.

So...you get fuzzy photos even when the LCD image in live view is sharp and only when the subject is at infinity? The final image should be at least as sharp as the LCD. Be aware that pixel peeping at the captured image of a distant subject will be intrinsically disappointing when compared to nearer subjects due to haze and intervening atmospheric variations. This is true with even the best lenses.

Steve

Thank you for quick response! But the picture from Macro lens is not even near as good as from kit Pentax 18-55 or 55-300 at longer focusing distances. So certainly it cannot be used as regular prime 50 mm for shooting everything.

oxidized · 11-30-2012, 10:07 AM

In general, shooting wide open at infinity produces results which are a lot fuzzier than than wide open up close. This could be further enhanced by the fact that macro lens are designed to perform better for up close shots and sometimes are not as great for landscape shots.

It is also hard to compare that lens to the Pentax 18-55 since the kit has a different max aperture and it is an all purpose lens.

pacopentax · 02-06-2013, 03:43 PM

Hi Bronmar

I have just bought that lens today and in my first 100 shots I have noticed the same problem you mention here. The photos are great at close range, but look awful at longer distance. I dont think that the lens is supposed to have such a bad performance with distant objects... ANY compact camera will look better than that!

However, the image does look perfectly sharp thru the finder at any distance.

I was wondering if the lens is defective, or there is a issue with the focus limit, or may be caused by the UV filter... Tomorrow I will try to shot without the filter, and without the limit... I will tell you what I find

pacopentax · 02-07-2013, 02:33 PM

I have been testing the lens again today in AF, MF with and without the focus limit.

I got very sharp pictures in MF, and also in AF, but some blurred ones with AF only.

I think the problem is caused by the AF. The lens has a beyond infinity position and I guess that the AF sometimes uses this set when you try to focus the horizon or the clouds. The result is a quite blurred image.

So, if you use this lens, I recomend MF when focusing to the infinity. Also, it is better to use a small aperture like F8 or smaller.

Hope this helps.

Bronmar · 02-07-2013, 08:06 PM

Hi Pacopentax,

Thank you for the testing. Anyway the primary use of this lens is macro. For that the lens is excellent.

11-29-2012, 06:38 PM	#1
Bronmar Junior Member Join Date: Jul 2012 Posts: 26	Sigma 50mm f/2.8 EX DG Macro infinity focus issue Has anyone had an issue with infinity focus using Sigma 50mm f/2.8 EX DG Macro. It's a perfect auto/manual focus in macro and short distances but it's always blurry for the subject further away from the lens. Even you can clearly see that it's in a perfect focus using auto/manual focusing (viewfinder or LV). The camera used is Pentax k r.

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11-29-2012, 08:56 PM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Hi! Welcome to Pentax Forums! I own a copy of that lens and have not had any focus issues at any point in its focus range. So...you get fuzzy photos even when the LCD image in live view is sharp and only when the subject is at infinity? The final image should be at least as sharp as the LCD. Be aware that pixel peeping at the captured image of a distant subject will be intrinsically disappointing when compared to nearer subjects due to haze and intervening atmospheric variations. This is true with even the best lenses. Steve

11-30-2012, 08:47 AM	#3
Bronmar Junior Member Join Date: Jul 2012 Posts: 26 Original Poster	Originally posted by stevebrot Hi! Welcome to Pentax Forums! I own a copy of that lens and have not had any focus issues at any point in its focus range. So...you get fuzzy photos even when the LCD image in live view is sharp and only when the subject is at infinity? The final image should be at least as sharp as the LCD. Be aware that pixel peeping at the captured image of a distant subject will be intrinsically disappointing when compared to nearer subjects due to haze and intervening atmospheric variations. This is true with even the best lenses. Steve Thank you for quick response! But the picture from Macro lens is not even near as good as from kit Pentax 18-55 or 55-300 at longer focusing distances. So certainly it cannot be used as regular prime 50 mm for shooting everything.

11-30-2012, 10:07 AM	#4
oxidized Veteran Member Join Date: Dec 2009 Location: USA - Delaware Photos: Albums Posts: 435	In general, shooting wide open at infinity produces results which are a lot fuzzier than than wide open up close. This could be further enhanced by the fact that macro lens are designed to perform better for up close shots and sometimes are not as great for landscape shots. It is also hard to compare that lens to the Pentax 18-55 since the kit has a different max aperture and it is an all purpose lens.

02-06-2013, 03:43 PM	#5
pacopentax New Member Join Date: Feb 2013 Posts: 2	Hi Bronmar I have just bought that lens today and in my first 100 shots I have noticed the same problem you mention here. The photos are great at close range, but look awful at longer distance. I dont think that the lens is supposed to have such a bad performance with distant objects... ANY compact camera will look better than that! However, the image does look perfectly sharp thru the finder at any distance. I was wondering if the lens is defective, or there is a issue with the focus limit, or may be caused by the UV filter... Tomorrow I will try to shot without the filter, and without the limit... I will tell you what I find

02-07-2013, 02:33 PM	#6
pacopentax New Member Join Date: Feb 2013 Posts: 2	I have been testing the lens again today in AF, MF with and without the focus limit. I got very sharp pictures in MF, and also in AF, but some blurred ones with AF only. I think the problem is caused by the AF. The lens has a beyond infinity position and I guess that the AF sometimes uses this set when you try to focus the horizon or the clouds. The result is a quite blurred image. So, if you use this lens, I recomend MF when focusing to the infinity. Also, it is better to use a small aperture like F8 or smaller. Hope this helps.

02-07-2013, 08:06 PM	#7
Bronmar Junior Member Join Date: Jul 2012 Posts: 26 Original Poster	Hi Pacopentax, Thank you for the testing. Anyway the primary use of this lens is macro. For that the lens is excellent.