K-x + SIgma 500mm f4.5 + Sigma TC 1.4 autofocus

PMunks · 06-11-2010, 11:45 AM

Originally posted by Asahiflex

By the way: I also tried the Sigma 500/4.5 with the SMC Pentax-F 1.7x AF adapter and I was really underwhelmed with the results. IMHO this combination is not recommended.

I won't bother trying then.

I don't know about the optics but I think the Sigma TC is a nice piece of engineering.

garyk · 06-22-2010, 09:03 AM

I have the sigma 300mm f2.8 lens and use the 2.0 tc whenever i can. The 1.4 is a shoe in.
But in low light. And i mean with some sun and the subject in the shade it is a very bad af problem.
I shoot birds and often in dark places. The 1.4 at f4 is great but the 2.0 at f5.6 is very slow on my k-7. I would hate to take it to 6.3 and try. But I have thought about this lens and wondered how it would work.
Thanks

PMunks · 06-23-2010, 03:23 AM

Originally posted by garyk

I have the sigma 300mm f2.8 lens and use the 2.0 tc whenever i can. The 1.4 is a shoe in.
But in low light. And i mean with some sun and the subject in the shade it is a very bad af problem.
I shoot birds and often in dark places. The 1.4 at f4 is great but the 2.0 at f5.6 is very slow on my k-7. I would hate to take it to 6.3 and try. But I have thought about this lens and wondered how it would work.
Thanks

It would be interesting to try the combination on a K-x.

Are you pleased with the lens? I was thinking about it but saw a used 500mm at a good price & I had to grab it if I wanted it.

With the 1.4x you have 420mm at F4 while I have 500mm at F4.5 but it is about 1Kg heavier.

PePe · 06-23-2010, 04:33 AM

Originally posted by PMunks

It would be interesting to try the combination on a K-x.

Are you pleased with the lens? I was thinking about it but saw a used 500mm at a good price & I had to grab it if I wanted it.

With the 1.4x you have 420mm at F4 while I have 500mm at F4.5 but it is about 1Kg heavier.

I have both the Sigma 300/2,8 and the 500/4,5 and use them frequently.
As such the 300/2,8 is a pretty good lens, but wide open the 500/4,5 is slightly sharper.
Combined with a TC the 300/2,8 is way behind in terms of optical performance, even with a 1,4 x TC.
Despite the weight penalty I would not consider this as a real alternative to the 500/4,5.

The 500/4,5 works reasonably well with the 1,4 x TC. AF is somewhat slower, but it usually works.
With the 2 x TC it is a MF lens.

Last edited by PePe; 06-23-2010 at 04:40 AM.

PMunks · 06-23-2010, 06:06 AM

I have a Pentax 300mm F4 which AF's quite well with my Pentax 1.7X TC so from what you say, I think I made the right choice for me.

When I want 500mm without the weight I use a Tamron 500mm F8 Mirror. With CIF & SR I find it a pretty good combination though obviously not as sharp.

Entropy · 06-23-2010, 07:18 AM

Originally posted by Lowell Goudge

impossible re AF limit

the bigma would not AF if this was the case.

Not sure where you got your info but there are just too many lenses at F6.3 to 6.7 which are sold by all lens makers for this maximum aperture to be a limit.

If you follow the forum threads frequently you will see a lot of dicsussion about the SMC-F 1.7x AF TC.

This works reliably on any F4 lens and the 1.7x factor translates to 510mm F7.1 I think. It has been reported to work on the SMC 500 F4.5 also, which would take you to F8 although I have no first hand experience of that. I do have first hand experience with the 1.7x TC on AF bodies back as far as the PZ-1 with no issue so the F7 limit for AF working has been around for some 20 years.

Where ever you got it, it is bad information.

It's a soft limit, and 5.6 is all Pentax will guarantee their AF system to. You can almost always go to 6.3 without problems, and sometimes even f/8 but at that point you'll be on the edge in any lighting condition.

Third-party manufacturers do extra testing to certify that their lenses work beyond the specified limit.

It's not about available light, it's actually about the lens physics - think of the classic split-prism viewfinders and how they would just go completely dark beyond a certain aperture regardless of the available light. Same concept for AF failing beyond a certain limit.

Hello_Photo · 06-24-2010, 07:55 AM

Re: Canon and the F5.6 limit for AF - I have read (and can't find the link right now) that the Canon firmware includes a self-crippling mechanism where if the camera body can determine that the combination of lens and TC will result in smaller aperture than F/5.6 (F/8 for the 1D series) it will disable AF. Read that carefully - the camera body is programmed to kill AF without trying if it thinks the aperture is smaller than a pre-defined limit. This is why some Canon users talk about various hacks to trick the camera body into believing it's just a lens attached by shorting pins so that the camera still tries to AF (which it often does successfully, within reasonable limits).

gary1952 · 06-26-2010, 12:57 AM

I must have a good copy of the 300mm f2.8 lens. I bought it new, it is the Ex DG Apo, about 6 months old now. But at 2.8 it is great close. But stopped down to 3.5 to 4 it is absolutly stunning.
And that goes for the T.C's. It follows the lens exactly. At 4.9 with the 1.4 T.C. It doesn't get any sharper. At F7 with the 2.o T.C. It is at it's sharpest.
Here is a pic I took last week.

I use the lens on a gimble mount almost always for good sharp and consistent pics. But with the 1.4 and shake enabled on the camera it is very good also. If you can punch up the shutter speed. I am getting old and have a hard time holdint it for very long.
Many times with the 300 and the 2.0 attached i focus manually first on the subject then switch over to auto focus and it hits very fast. If not sometimes it is very slow. In low light it is a must to manual focus first I have found on my copy. But then it will hit after MF is close usually.

When used properly I don't see how the eye can pick up anymore detail.
I have many pics this good and better.

But I am thinking seriously about getting the 500mm f4.5 because with a T.C. on a pentax it will give me a 700mm lens. with minumum drop off in imige i hope.
With the 1.4 T.c. on the 300mm it is better but you must get very close to birds.
That is my copy if the 300 mm f2.8.

If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it.

This is with the 300mm + 2.0T.C. F7 and -.7.

PMunks · 06-26-2010, 02:23 AM

Originally posted by gary1952

If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it.

A very nice picture.

Both the 500mm F4.5 & the 1.4x TC are pretty new to me & I haven't put anything online yet, but when I do, I will certainly send you a link.

PePe · 06-26-2010, 02:31 AM

Originally posted by gary1952

But I am thinking seriously about getting the 500mm f4.5 because with a T.C. on a pentax it will give me a 700mm lens. with minumum drop off in imige i hope.
With the 1.4 T.c. on the 300mm it is better but you must get very close to birds.
That is my copy if the 300 mm f2.8.

If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it.

This is with the 300mm + 2.0T.C. F7 and -.7.

Just PM´d you a longer description of my experience with the Sigma500/4,5.
You might also want to have a look into
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/59187-sigma-50...est-shots.html
Please bear in mind that these pictures were sent as attachments and have therefor been compressed quite alot, leading to a significant loss of colour intensity.

06-26-2010, 12:57 AM	#23
gary1952 Inactive Account Join Date: Feb 2010 Location: thailand Posts: 45	I must have a good copy of the 300mm f2.8 lens. I bought it new, it is the Ex DG Apo, about 6 months old now. But at 2.8 it is great close. But stopped down to 3.5 to 4 it is absolutly stunning. And that goes for the T.C's. It follows the lens exactly. At 4.9 with the 1.4 T.C. It doesn't get any sharper. At F7 with the 2.o T.C. It is at it's sharpest. Here is a pic I took last week. I use the lens on a gimble mount almost always for good sharp and consistent pics. But with the 1.4 and shake enabled on the camera it is very good also. If you can punch up the shutter speed. I am getting old and have a hard time holdint it for very long. Many times with the 300 and the 2.0 attached i focus manually first on the subject then switch over to auto focus and it hits very fast. If not sometimes it is very slow. In low light it is a must to manual focus first I have found on my copy. But then it will hit after MF is close usually. When used properly I don't see how the eye can pick up anymore detail. I have many pics this good and better. But I am thinking seriously about getting the 500mm f4.5 because with a T.C. on a pentax it will give me a 700mm lens. with minumum drop off in imige i hope. With the 1.4 T.c. on the 300mm it is better but you must get very close to birds. That is my copy if the 300 mm f2.8. If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it. This is with the 300mm + 2.0T.C. F7 and -.7. Last edited by gary1952; 06-26-2010 at 01:17 AM.

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06-11-2010, 11:45 AM	#16
PMunks Inactive Account Join Date: Nov 2009 Location: Norfolk Posts: 39 Original Poster	Originally posted by Asahiflex By the way: I also tried the Sigma 500/4.5 with the SMC Pentax-F 1.7x AF adapter and I was really underwhelmed with the results. IMHO this combination is not recommended. I won't bother trying then. I don't know about the optics but I think the Sigma TC is a nice piece of engineering.

06-22-2010, 09:03 AM	#17
garyk Inactive Account Join Date: Feb 2010 Photos: Gallery Posts: 488	I have the sigma 300mm f2.8 lens and use the 2.0 tc whenever i can. The 1.4 is a shoe in. But in low light. And i mean with some sun and the subject in the shade it is a very bad af problem. I shoot birds and often in dark places. The 1.4 at f4 is great but the 2.0 at f5.6 is very slow on my k-7. I would hate to take it to 6.3 and try. But I have thought about this lens and wondered how it would work. Thanks

06-23-2010, 03:23 AM	#18
PMunks Inactive Account Join Date: Nov 2009 Location: Norfolk Posts: 39 Original Poster	Originally posted by garyk I have the sigma 300mm f2.8 lens and use the 2.0 tc whenever i can. The 1.4 is a shoe in. But in low light. And i mean with some sun and the subject in the shade it is a very bad af problem. I shoot birds and often in dark places. The 1.4 at f4 is great but the 2.0 at f5.6 is very slow on my k-7. I would hate to take it to 6.3 and try. But I have thought about this lens and wondered how it would work. Thanks It would be interesting to try the combination on a K-x. Are you pleased with the lens? I was thinking about it but saw a used 500mm at a good price & I had to grab it if I wanted it. With the 1.4x you have 420mm at F4 while I have 500mm at F4.5 but it is about 1Kg heavier.

06-23-2010, 04:33 AM	#19
PePe Pentaxian Join Date: Nov 2007 Location: Helsinki, Finland Photos: Gallery \| Albums Posts: 597	Originally posted by PMunks It would be interesting to try the combination on a K-x. Are you pleased with the lens? I was thinking about it but saw a used 500mm at a good price & I had to grab it if I wanted it. With the 1.4x you have 420mm at F4 while I have 500mm at F4.5 but it is about 1Kg heavier. I have both the Sigma 300/2,8 and the 500/4,5 and use them frequently. As such the 300/2,8 is a pretty good lens, but wide open the 500/4,5 is slightly sharper. Combined with a TC the 300/2,8 is way behind in terms of optical performance, even with a 1,4 x TC. Despite the weight penalty I would not consider this as a real alternative to the 500/4,5. The 500/4,5 works reasonably well with the 1,4 x TC. AF is somewhat slower, but it usually works. With the 2 x TC it is a MF lens. Last edited by PePe; 06-23-2010 at 04:40 AM.

06-23-2010, 06:06 AM	#20
PMunks Inactive Account Join Date: Nov 2009 Location: Norfolk Posts: 39 Original Poster	I have a Pentax 300mm F4 which AF's quite well with my Pentax 1.7X TC so from what you say, I think I made the right choice for me. When I want 500mm without the weight I use a Tamron 500mm F8 Mirror. With CIF & SR I find it a pretty good combination though obviously not as sharp.

06-23-2010, 07:18 AM	#21
Entropy Veteran Member Join Date: Jun 2007 Location: Owego, NY Posts: 976	Originally posted by Lowell Goudge impossible re AF limit the bigma would not AF if this was the case. Not sure where you got your info but there are just too many lenses at F6.3 to 6.7 which are sold by all lens makers for this maximum aperture to be a limit. If you follow the forum threads frequently you will see a lot of dicsussion about the SMC-F 1.7x AF TC. This works reliably on any F4 lens and the 1.7x factor translates to 510mm F7.1 I think. It has been reported to work on the SMC 500 F4.5 also, which would take you to F8 although I have no first hand experience of that. I do have first hand experience with the 1.7x TC on AF bodies back as far as the PZ-1 with no issue so the F7 limit for AF working has been around for some 20 years. Where ever you got it, it is bad information. It's a soft limit, and 5.6 is all Pentax will guarantee their AF system to. You can almost always go to 6.3 without problems, and sometimes even f/8 but at that point you'll be on the edge in any lighting condition. Third-party manufacturers do extra testing to certify that their lenses work beyond the specified limit. It's not about available light, it's actually about the lens physics - think of the classic split-prism viewfinders and how they would just go completely dark beyond a certain aperture regardless of the available light. Same concept for AF failing beyond a certain limit.

06-24-2010, 07:55 AM	#22
Hello_Photo Forum Member Join Date: Apr 2009 Location: Canada Posts: 75	Re: Canon and the F5.6 limit for AF - I have read (and can't find the link right now) that the Canon firmware includes a self-crippling mechanism where if the camera body can determine that the combination of lens and TC will result in smaller aperture than F/5.6 (F/8 for the 1D series) it will disable AF. Read that carefully - the camera body is programmed to kill AF without trying if it thinks the aperture is smaller than a pre-defined limit. This is why some Canon users talk about various hacks to trick the camera body into believing it's just a lens attached by shorting pins so that the camera still tries to AF (which it often does successfully, within reasonable limits).

06-26-2010, 02:23 AM	#24
PMunks Inactive Account Join Date: Nov 2009 Location: Norfolk Posts: 39 Original Poster	Originally posted by gary1952 If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it. A very nice picture. Both the 500mm F4.5 & the 1.4x TC are pretty new to me & I haven't put anything online yet, but when I do, I will certainly send you a link.

06-26-2010, 02:31 AM	#25
PePe Pentaxian Join Date: Nov 2007 Location: Helsinki, Finland Photos: Gallery \| Albums Posts: 597	Originally posted by gary1952 But I am thinking seriously about getting the 500mm f4.5 because with a T.C. on a pentax it will give me a 700mm lens. with minumum drop off in imige i hope. With the 1.4 T.c. on the 300mm it is better but you must get very close to birds. That is my copy if the 300 mm f2.8. If the O.P. will PM me or give me links to your pics with the 500mm and the 500 with the 1.4 attached i would very much appreciate it. This is with the 300mm + 2.0T.C. F7 and -.7. Just PM´d you a longer description of my experience with the Sigma500/4,5. You might also want to have a look into https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/59187-sigma-50...est-shots.html Please bear in mind that these pictures were sent as attachments and have therefor been compressed quite alot, leading to a significant loss of colour intensity.