Re: Telephone call with Sigma re 18-35

Parallax · 02-18-2015, 09:25 AM

Originally posted by MadMathMind

The sensor has no effect on autofocus through the viewfinder.

Correct. It can't possibly as the light doesn't reach the sensor until the picture is taken; a point at which the lens has already acquired (or not) focus.

candgpics · 02-18-2015, 01:10 PM

Hi. The Sigma technician was very clear about his/Sigma's position regarding the "ancient"dslr focusing systems.

I have seen similar reports of focusing issues with the Nikon version, though, there appear to be more reported problems with the Pentax mount version--perhaps as a consequence of fewer lenses sold in the Pentax mount.

Digitalis, I might be mistaken, and forgive me if I am, but I thought the USB doc did not solve the focusing issue for you. Am I incorrect? If it has worked for you I might be willing to give it a try.

**Digitalis** · 02-18-2015, 05:31 PM - **1 Like**

Originally posted by candgpics

igitalis, I might be mistaken, and forgive me if I am, but I thought the USB doc did not solve the focusing issue for you. Am I incorrect?

it didn't eliminate all of the AF issues, but the lens is more consistent now. I can predict when the lens most most likely to give me a false positive. The AF on my lens is about 78% accurate, which is better than nothing.

It is important to note that the AF adjustment on Pentax Dslrs is not sufficient for a lens like this, you need to be able to adjust the focus at each focal length, which is what the sigma lens dock allows you to do. Globally adjusting the lens isn't going to solve your problems - it is probably going to make them worse.

Parallax · 02-18-2015, 05:52 PM

What I find interesting about this is the position of "there's a problem with this lens on all DSLRs so, clearly, it's a problem with DSLRs".

**Digitalis** · 02-18-2015, 06:04 PM

I know, Sigma hasn't exactly been forthcoming with information when a specific lens has been having issues on all makes of DSLR.

MadMathMind · 02-18-2015, 06:07 PM

Originally posted by Parallax

What I find interesting about this is the position of "there's a problem with this lens on all DSLRs so, clearly, it's a problem with DSLRs".

I can't believe that the company would hold that position. Sigma's own cameras don't have some revolutionary technology on them.

Parallax · 02-18-2015, 06:12 PM

Well, that's the way I interpret what the OP says they told him.

**Digitalis** · 02-18-2015, 06:28 PM

Originally posted by MadMathMind

Sigma's own cameras don't have some revolutionary technology on them.

Foveon - it solves all your problems.

candgpics · 02-18-2015, 09:04 PM - **1 Like**

Hi:

I just wanted to follow-up a bit on my call with Sigma. Though I am not as knowledgeable in optics as I would like, my summary of what the technician told me is accurate. He certainly was very responsive and took the time to speak with me, but he made it clear that he/Sigma felt the issue was with general dslr/af design (though I made it clear I was a Pentax owner). He did not limit this comment to Pentax--but he did note that the shake reduction (whether it was on or off) was another factor that complicated matters, essentially noting that the way the sensor is mounted introduces another variable. He also made it clear that he felt many owners who micro adjusted the lens were doing so incorrectly.

I asked about the USB doc, along the lines of what Digitalis noted, because I read the follow-up pentaxforums af review noting that the USB dock did address the issue at the very specific parameters for which the USB doc adjusts the lens--but did not provide an overall fix once one started to shoot at parameters not adjusted by the software.

I am flummoxed and disappointed.

Nonetheless, I adjusted globally, 35 mm, f 1.8, 1 meter distance, center point, on a tripod, SR off, and as always, RAW, 3 pictures at each micro adjustment -10 through +10.

There was a very slight variation even among the same adjustment on a few occasions, but it was minor (i.e., three shots at -3 might have one that looks slightly in better or worse focus than the other two). An adjustment of -1 seemed to work the best, which is not very much.

When I have some time I will take pictures around the house, first at 35mm. If the adjustment works and the af is not creating random/repetitive errors (for whatever reason) than at least I know 35mm is set. Then I will consider getting the dock for the other settings, but I go back and forth. I really am not looking to confirm the pentaxforums follow-up af/USB testing which concluded that once outside the adjusted parameters using the dock, problems still occurred.

Though, Digitalis, you have a high majority of your pictures in focus and seem to have learned the lens' quirks, I am not sure I want to keep another quirky lens, but we'll see. Perhaps, if the lens is"that good" when it is "on" I may simply take multiple pictures for critical images.

Onward.

**Digitalis** · 02-18-2015, 11:48 PM

Originally posted by candgpics

I asked about the USB doc, along the lines of what Digitalis noted, because I read the follow-up pentaxforums af review noting that the USB dock did address the issue at the very specific parameters for which the USB doc adjusts the lens--but did not provide an overall fix once one started to shoot at parameters not adjusted by the software.

I posted my own comparative review of the Sigma 18-35mm f/1.8 ART - there was an interesting discussion of exactly the issues you have been encountering.

Originally posted by candgpics

Digitalis, you have a high majority of your pictures in focus and seem to have learned the lens' quirks, I am not sure I want to keep another quirky lens, but we'll see

I have a collection of quirky lenses.

Driline · 02-19-2015, 05:20 AM

Sigma should have a disclaimer: WARNING This lens may take hours,weeks, months to properly adjust focus to your DSLR , and even then may or may not focus

Parallax · 02-19-2015, 05:57 AM - **2 Likes**

"It's a problem with DSLR design in general, not our lens design."
Right, just like the problem with automotive design. They're all made to use round tires so it's their fault the square tire I just invented doesn't work right.

**Digitalis** · 02-19-2015, 10:36 PM

Originally posted by Parallax

...like the problem with automotive design. They're all made to use round tires so it's their fault the square tire I just invented doesn't work right.

Mythbusters had a lot of fun with that:

candgpics · 02-20-2015, 04:29 AM

Digital Is, does the USB dock permit one to adjust the lens on multiple camera bodies? Doesn't the dock adjust the lens itself? Or, does the lens have the ability to store settings for more than one camera body?

**Digitalis** · 02-20-2015, 05:27 AM

Originally posted by candgpics

does the USB dock permit one to adjust the lens on multiple camera bodies?

The dock is for adjusting the lens itself. It works with the lens only. However different adjustment values can be stored as profiles fir different cameras, however you need to dock the lens to apply the camera specific AF settings.

Originally posted by candgpics

Doesn't the dock adjust the lens itself?

You need an AF calibration chart to ascertain the degree of correction needed.

Originally posted by candgpics

does the lens have the ability to store settings for more than one camera body?

No, the profiles for lens correction can be stored on your computer and the dock is used to apply them.

02-18-2015, 09:04 PM - 1 Like	#24
candgpics Veteran Member Join Date: Feb 2009 Location: Maine, USA Posts: 394 Original Poster	Hi: I just wanted to follow-up a bit on my call with Sigma. Though I am not as knowledgeable in optics as I would like, my summary of what the technician told me is accurate. He certainly was very responsive and took the time to speak with me, but he made it clear that he/Sigma felt the issue was with general dslr/af design (though I made it clear I was a Pentax owner). He did not limit this comment to Pentax--but he did note that the shake reduction (whether it was on or off) was another factor that complicated matters, essentially noting that the way the sensor is mounted introduces another variable. He also made it clear that he felt many owners who micro adjusted the lens were doing so incorrectly. I asked about the USB doc, along the lines of what Digitalis noted, because I read the follow-up pentaxforums af review noting that the USB dock did address the issue at the very specific parameters for which the USB doc adjusts the lens--but did not provide an overall fix once one started to shoot at parameters not adjusted by the software. I am flummoxed and disappointed. Nonetheless, I adjusted globally, 35 mm, f 1.8, 1 meter distance, center point, on a tripod, SR off, and as always, RAW, 3 pictures at each micro adjustment -10 through +10. There was a very slight variation even among the same adjustment on a few occasions, but it was minor (i.e., three shots at -3 might have one that looks slightly in better or worse focus than the other two). An adjustment of -1 seemed to work the best, which is not very much. When I have some time I will take pictures around the house, first at 35mm. If the adjustment works and the af is not creating random/repetitive errors (for whatever reason) than at least I know 35mm is set. Then I will consider getting the dock for the other settings, but I go back and forth. I really am not looking to confirm the pentaxforums follow-up af/USB testing which concluded that once outside the adjusted parameters using the dock, problems still occurred. Though, Digitalis, you have a high majority of your pictures in focus and seem to have learned the lens' quirks, I am not sure I want to keep another quirky lens, but we'll see. Perhaps, if the lens is"that good" when it is "on" I may simply take multiple pictures for critical images. Onward. Last edited by candgpics; 02-18-2015 at 09:18 PM.

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02-18-2015, 09:25 AM	#16
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,333	Originally posted by MadMathMind The sensor has no effect on autofocus through the viewfinder. Correct. It can't possibly as the light doesn't reach the sensor until the picture is taken; a point at which the lens has already acquired (or not) focus.

02-18-2015, 01:10 PM	#17
candgpics Veteran Member Join Date: Feb 2009 Location: Maine, USA Posts: 394 Original Poster	Hi. The Sigma technician was very clear about his/Sigma's position regarding the "ancient"dslr focusing systems. I have seen similar reports of focusing issues with the Nikon version, though, there appear to be more reported problems with the Pentax mount version--perhaps as a consequence of fewer lenses sold in the Pentax mount. Digitalis, I might be mistaken, and forgive me if I am, but I thought the USB doc did not solve the focusing issue for you. Am I incorrect? If it has worked for you I might be willing to give it a try.

02-18-2015, 05:31 PM - 1 Like	#18
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by candgpics igitalis, I might be mistaken, and forgive me if I am, but I thought the USB doc did not solve the focusing issue for you. Am I incorrect? it didn't eliminate all of the AF issues, but the lens is more consistent now. I can predict when the lens most most likely to give me a false positive. The AF on my lens is about 78% accurate, which is better than nothing. It is important to note that the AF adjustment on Pentax Dslrs is not sufficient for a lens like this, you need to be able to adjust the focus at each focal length, which is what the sigma lens dock allows you to do. Globally adjusting the lens isn't going to solve your problems - it is probably going to make them worse.

02-18-2015, 05:52 PM	#19
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,333	What I find interesting about this is the position of "there's a problem with this lens on all DSLRs so, clearly, it's a problem with DSLRs".

02-18-2015, 06:04 PM	#20
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	I know, Sigma hasn't exactly been forthcoming with information when a specific lens has been having issues on all makes of DSLR.

02-18-2015, 06:07 PM	#21
MadMathMind Veteran Member Join Date: Dec 2013 Location: Houston, TX Photos: Gallery Posts: 1,717	Originally posted by Parallax What I find interesting about this is the position of "there's a problem with this lens on all DSLRs so, clearly, it's a problem with DSLRs". I can't believe that the company would hold that position. Sigma's own cameras don't have some revolutionary technology on them.

02-18-2015, 06:12 PM	#22
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,333	Well, that's the way I interpret what the OP says they told him.

02-18-2015, 06:28 PM	#23
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by MadMathMind Sigma's own cameras don't have some revolutionary technology on them. Foveon - it solves all your problems.

02-18-2015, 11:48 PM	#25
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by candgpics I asked about the USB doc, along the lines of what Digitalis noted, because I read the follow-up pentaxforums af review noting that the USB dock did address the issue at the very specific parameters for which the USB doc adjusts the lens--but did not provide an overall fix once one started to shoot at parameters not adjusted by the software. I posted my own comparative review of the Sigma 18-35mm f/1.8 ART - there was an interesting discussion of exactly the issues you have been encountering. Originally posted by candgpics Digitalis, you have a high majority of your pictures in focus and seem to have learned the lens' quirks, I am not sure I want to keep another quirky lens, but we'll see I have a collection of quirky lenses.

02-19-2015, 05:20 AM	#26
Driline Pentaxian Join Date: Dec 2012 Location: IOWA Where the Tall Corn Grows Photos: Gallery Posts: 3,704	Sigma should have a disclaimer: WARNING This lens may take hours,weeks, months to properly adjust focus to your DSLR , and even then may or may not focus

02-19-2015, 05:57 AM - 2 Likes	#27
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,333	"It's a problem with DSLR design in general, not our lens design." Right, just like the problem with automotive design. They're all made to use round tires so it's their fault the square tire I just invented doesn't work right.

02-19-2015, 10:36 PM	#28
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by Parallax ...like the problem with automotive design. They're all made to use round tires so it's their fault the square tire I just invented doesn't work right. Mythbusters had a lot of fun with that:

02-20-2015, 04:29 AM	#29
candgpics Veteran Member Join Date: Feb 2009 Location: Maine, USA Posts: 394 Original Poster	Digital Is, does the USB dock permit one to adjust the lens on multiple camera bodies? Doesn't the dock adjust the lens itself? Or, does the lens have the ability to store settings for more than one camera body?

02-20-2015, 05:27 AM	#30
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by candgpics does the USB dock permit one to adjust the lens on multiple camera bodies? The dock is for adjusting the lens itself. It works with the lens only. However different adjustment values can be stored as profiles fir different cameras, however you need to dock the lens to apply the camera specific AF settings. Originally posted by candgpics Doesn't the dock adjust the lens itself? You need an AF calibration chart to ascertain the degree of correction needed. Originally posted by candgpics does the lens have the ability to store settings for more than one camera body? No, the profiles for lens correction can be stored on your computer and the dock is used to apply them.