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09-15-2007, 08:24 AM   #1
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Bigma Owners & Teleconvertors

I have had the Bigma less than a week and already I want more reach haha. So my question is what teleconvertors have you used and what is your experience with them? As I understand it 1.4x looses one stop not sure on 1.7x and 2x would loose two stops.

I am not overly concerned on the stops as these would be used either in good lighting conditions or long exposures ,but then again , I will defer to those of your that have some experience with this.

Will a teleconvertor work on all Pentax Lens ( not that you would use them on all , just wondering if you can) ? Suppose I pick up a DA* 50-135 . Suppose I get a Sigma or Tamron converter will they work on the DA* * will a Pentax work on the Sigma ? Stupid questions perhaps just want to make sure.

I would appreciate any feedback as to what works for you, what brand and if you have used it on other lens.

Thanks.

09-15-2007, 08:41 AM   #2
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I can help a little bit. I have a Sigma 50-500mm "Bigma". I also have a Tamron 1.4x TC.

If you buy the Sigma Teleconverters you must lock your Bigma in the "100-Converter" position or you risk damaging both the TC and the Lens. The Sigma TC extends into the lens a bit and the Bigma lens, at focal lengths less than 100mm extends too far back toward the mount and they will collide. The Tamron TC does not extend into the lens at all so you can install it at any focal length.

The tamron TC should work on just about any lens. I think you may run into problems trying to install the Sigma on some lenses for the same reason there are restrictions for using it on the Bigma.

Since I dont have a Sigma TC I cant tell you from experience. I'm just making an assumption. I do have the Tamron TC and I can install it on every lens I have.
09-15-2007, 05:36 PM   #3
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QuoteOriginally posted by Mr Hyde Quote
I can help a little bit. I have a Sigma 50-500mm "Bigma". I also have a Tamron 1.4x TC.

If you buy the Sigma Teleconverters you must lock your Bigma in the "100-Converter" position or you risk damaging both the TC and the Lens. The Sigma TC extends into the lens a bit and the Bigma lens, at focal lengths less than 100mm extends too far back toward the mount and they will collide. The Tamron TC does not extend into the lens at all so you can install it at any focal length.

The tamron TC should work on just about any lens. I think you may run into problems trying to install the Sigma on some lenses for the same reason there are restrictions for using it on the Bigma.

Since I dont have a Sigma TC I cant tell you from experience. I'm just making an assumption. I do have the Tamron TC and I can install it on every lens I have.
Thanks Mr Hyde - I will look at the Tamron one - does AF work I would assume it is a little slower ? Can anybody vouch for the Pentax model ?
09-15-2007, 07:42 PM   #4
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QuoteOriginally posted by daacon Quote
Thanks Mr Hyde - I will look at the Tamron one - does AF work I would assume it is a little slower ? Can anybody vouch for the Pentax model ?

AF works on lenses f/4 or faster. Slower lenses are hit and miss, mostly miss.

09-16-2007, 01:53 AM   #5
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Says in the manual for the Bigma the 1.4X TC is manual focus only. I've not used the two in conjunction yet. Will have to get onto that...
09-16-2007, 02:50 AM   #6
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SIGMA EX DG 50-500 f4-6.3

A 1.4x teleconverter will make it a 70-700 f5.6-9, a 1.7 a 85-850 f6.7-11, a 2.0 a 100-1000 f8-13 (roughly).

Even 700 @ f9 would not be very usable. Why do you want more reach? You're talking equivalent 750mm as is.
09-16-2007, 04:14 AM   #7
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At 500mm end, the image can be unsharp with little contrast given the long distance between subject and camera. Using an extra tele would definitely jeopardise the image quality for sure and it would be too dark to use. If you could grab any examples, please share with us. Really eager to see the results of it
09-17-2007, 05:11 AM   #8
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'Why' do I 'need' more length? Well at this point it is the 'Mountain' reason - because it is there (so no real reason). I want to dabble at night (sky / moon / stars) pictures but you raise a good point I should give it a go with what I have first.

My eyes are not what they used to be and the last couple of years I have had to wear reading glasses (frick !!) - thus the question on AF - I need to find a better set up with my LowPro Sling 200 , Camera , and glasses all sting around my shoulders and neck - I don't find I need to glasses to look through the viewfinder (yet anyway) - however to read the menu or LCD screen - my arms are no longer long enough for my eyes to focus (I have AF issues with small print!) so glasses it is

Another reason for the teleconvertor is I want to get one or more of the DA* at some point I think. I want to wait for the DA* 60-250 - f4. Or perhaps the 300mm prime which is also f4.

Mr Hyde mentioned that a teleconvertor will only work with f4 and faster - if this is true then I may re-evaluate the need for a teleconvertor.

Thanks for the replies all.

09-17-2007, 05:31 AM   #9
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I do not know the BIGMA well enough to comment totally, but one thing everyone is missing here is the issue that on any lens with maximum apature less than F/4, the Pentax 1.7 x AF TC will NOT focus at all (there may be some reports that it works at f/4.5 but that is it) On any other lens, such as an F/5.6 even the 1.4X TC will not work reliably. As a result, what you are doing is converting these AF lenses into manual focus only lenses.

Why is this a bad thing?

Go back to my initial statement, I don't know the BIGMA, but I do know some other long sigma lenses. I have the APO 70-200 F/2.8 DG. It works well in AF, but I would NEVER use it in manual focus. The focusing collar has only 90 degrees of rotation to cover from 6 feet to infinity. Precision of focusing is impossible. By comparison, my SMC-P 300 f/4 has more than 270 degrees of rotation on the focusing collar, and my vivitar 400 mmf/5.6 has more than 300 degrees of rotation of the focusing collar.

These lenses were designed to be manual focus, and have the range of motion that makes manual focusing precise.

My sigma, with 90 degrees of rotation on the focusing collar, is clearly not intended to be manually focused.

ps. my celestron C90 spotting scope has abnout 1000 degrees of rotation on the focusing collar (3 turns) If you want to go long, get something precise.
09-17-2007, 02:28 PM   #10
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QuoteOriginally posted by daacon Quote

Mr Hyde mentioned that a teleconvertor will only work with f4 and faster - if this is true then I may re-evaluate the need for a teleconvertor.

Thanks for the replies all.
Actually I think I said that Autofocus will only work with f4 or faster. The TC will still work on slower lenses but will render them as manual focus only. (just a technical correction)
09-17-2007, 03:29 PM   #11
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QuoteOriginally posted by Mr Hyde Quote
Actually I think I said that Autofocus will only work with f4 or faster. The TC will still work on slower lenses but will render them as manual focus only. (just a technical correction)
Yes indeed I knew what I meant and what you said - albeit my articulation sucked
09-17-2007, 03:36 PM   #12
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I just did some study on this for my own personal interest. I was looking at purchasing 1.4x that was available at a knockdown price recently.

Google for Bigma and Teleconvertor and you will find that it has been discussed at length on some other forums that deal with Bird and Aircraft photography. Look around the Canon and Nikon forums also

The consensus of opinion is that 1.4x effectively ruins the IQ of each and every image taken with the Bigma. It is known to cause excessive CA and when used at the long end of the Bigma's range the focusing is so difficult as to be almost impossible to get a sharp image. Even focusing without the TC and then adding it in does not really cut it.

In short it's not a smart move.

I guess you would do better in getting a tripod for the Bigma so as to be as steady as possible and then crop the image to get what you want from it. If you shoot RAW you should be able to get images large enough to be usable.


Having said all that, if you still have the money burning a hole a in you pocket please do go ahead as I think we would all be interested in seeing the results posted here first hand as it were.
09-17-2007, 06:35 PM   #13
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Thanks Trawlerman - the extra $$ has successfully burnt my pants at this point. I think I may get one eventually but not until I get a fast 50-135 or the 60-250 or 300 prime. Soooooooooooo many wants (needs)

I thought Adam (mo) had a picture with a Bigma and a 1.4 or 1.7 ... some antenna where you could see the threads on the bolts. Maybe is was not a Bigma..
09-17-2007, 09:19 PM   #14
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QuoteOriginally posted by daacon Quote
Thanks Trawlerman - the extra $$ has successfully burnt my pants at this point. I think I may get one eventually but not until I get a fast 50-135 or the 60-250 or 300 prime. Soooooooooooo many wants (needs)

I thought Adam (mo) had a picture with a Bigma and a 1.4 or 1.7 ... some antenna where you could see the threads on the bolts. Maybe is was not a Bigma..
Dave, I would only use a TC with either a telephoto prime or F2.8 zoom.

I have the instruction sheet for the Tamron 1.4x and 2x TCs and I can confirm it says that autofocus will work only with F4 or faster and that lenses should be at least 50mm in focal length. I've had autofocus work, sort of, at F5.6-6.7 but only under very bright light.

You can try out one of my TC's on your 50-500 if you want. I just acquired an old Takumar 400mm prime and I'll bet that it will give better images with a TC than the 50-500 at the long end.

If I can make another suggestion. It will make a world of difference if you get a really good tripod and ballhead (Arca Swiss, Markins, Kirk, RRS, Acratech). Or, better yet, a good tripod + gimbal mount. At the very least get a monopod if you don't have one.

Let me know by PM if you want to try a TC out.
-George
09-18-2007, 07:03 AM   #15
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QuoteOriginally posted by Lowell Goudge Quote
I do not know the BIGMA well enough to comment totally, but one thing everyone is missing here is the issue that on any lens with maximum apature less than F/4, the Pentax 1.7 x AF TC will NOT focus at all (there may be some reports that it works at f/4.5 but that is it) On any other lens, such as an F/5.6 even the 1.4X TC will not work reliably. As a result, what you are doing is converting these AF lenses into manual focus only lenses.

Why is this a bad thing?

Go back to my initial statement, I don't know the BIGMA, but I do know some other long sigma lenses. I have the APO 70-200 F/2.8 DG. It works well in AF, but I would NEVER use it in manual focus. The focusing collar has only 90 degrees of rotation to cover from 6 feet to infinity. Precision of focusing is impossible. By comparison, my SMC-P 300 f/4 has more than 270 degrees of rotation on the focusing collar, and my vivitar 400 mmf/5.6 has more than 300 degrees of rotation of the focusing collar.

These lenses were designed to be manual focus, and have the range of motion that makes manual focusing precise.

My sigma, with 90 degrees of rotation on the focusing collar, is clearly not intended to be manually focused.

ps. my celestron C90 spotting scope has abnout 1000 degrees of rotation on the focusing collar (3 turns) If you want to go long, get something precise.
Hey Lowell, how do you find your C90 spotting scope compared to your other lenses? Is it plagued with the usual mirror lens woes? I had a Vivitar 500mm for a short time and it was a real pain to focus because I could barely see the viewfinder and my split microprism aid kept going dark haha. Light fall off and corner softness was really really bad...to the point where I totally forgot about the doughnut highlights.
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