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Old Apr 7, 2010, 3:35 PM   #1
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Default auto Teleconverter

My 28-200 tammy isnt the best reach for birds and wild life but I am enjoying the lens.

How would a X2 TC affect IQ and AF speeds? is there x2 teleconverters that allow for auto focusing still ? If i am going to be stuck with manual focus, I might as well just use the 500mm prime I have.

I dont find a lot of good times when the 500mm prime comes in handy so this was a bit of a failed buy. I need the remote to properly use this and it requires I lug around my extremely heavy Bogen Tripod.

I am completely new to wild life photography so I know my skills are not up to par but Im finding the hinderance of range is already a problem. With the tammy, I must pretty much be at near spitting range to still produce a nice up close shot and still have it crisp.


Well, to get down to it I did just purchase a Sigma 70-300 lens for fairly reasonable price.

At first i found a few stellar reviews that made the decision easy for the price but now with it in the mail Im regretting it a bit.

Should I have just bought a X2 teleconverter for my 28-200 instead of the 70-300?

I guess perhaps only time can tell. Im asking about the teleconverter because I want to know if I should just save my breath and not even open the sigma 70-300 when i get it and resell as brand new, or just return it ??

I cant afford the DA* lenses with nice reach so my budget was under 200.

Any thoughts/suggestions ?
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Old Apr 7, 2010, 11:09 PM   #2
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Keep the 70-300. The only 2x TC I tried was lousy and that seems to be the general consensus. 1.4 or 1.7 at the most are OK, but you lose too much quality when you go to 2x. Well, I shouldn't say the 2x TC is a complete loss - I took the glass out and use it occasionally as an extension tube. Works quite well for that.
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Old Apr 8, 2010, 1:18 PM   #3
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thanks for the response. Not that it matters because you shto down any want for getting a teleconverter, but if a teleconverter is attatched, do you lost auto features?
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Old Apr 8, 2010, 3:21 PM   #4
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Depends on both the lens and the TC. Some TCs provide contacts to let the camera completely talk to the lens, which theoretically allows for AF lenses to focus and would allow for auto exposure. Reality is that a slow lens may or may not auto focus - you lose light with a TC so you might not have enough for the lens to focus. TCs work best with faster lenses, like f4 or faster.

The TC I had was a manual one - no contacts. So any lens mounted on it became a manual lens (it had the lever so the camera could stop down the lens. Works fine for any lens that has an aperture ring and is manual focus anyway).

There's a Pentax TC that's a 1.7 that has the ability to AF (somewhat). The TC itself has a focus mechanism, it's somewhat limited so isn't like AF on a lens, but it does help focus a manual lens. Birders love it - use the A*300, focus to infinity and the TC will adjust if the bird is a bit closer than that. I'd love to have one, but can't afford the huge price they are going for right now. Scott can give you more information about them - he has several and uses them all the time.

There have been reports that Kenko's TC with the power zoom contacts may be able to allow the camera to AF SDM lenses, but they weren't designed for that and it seems like it's a hit-or-miss thing. Otherwise, no TC currently allows for AF of SDM lenses. Since you are talking about Tammy lens without SDM, that wouldn't matter to you.
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Old Apr 8, 2010, 10:33 PM   #5
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"but can't afford the huge price"

Stop right there. That sounds amazing but It'll have to wait a bit ;-)

You are so knowledgeable about lenses, thanks for all the info. I only have four semi fast lenses right now and they are all manual. 135mm 2.8 55mm 1.8 50mm 2.8 40-80mm 2.8. I can't really see a benefit of sticking the TC on the lenses I have now as I like to use them for their sharpness and bold colors (135 and 55 esp.) I am pleased to be both more educated and not without 1 dollar less. :-)
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Old Apr 12, 2010, 9:36 PM   #6
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The nature of TCs is to spread the light from the lens over a larger area - this is what causes the light loss, and also magnifies any imperfections in the lens, as well as introducing its own imperfections. Inexpensive TCs can cause enough quality loss to make it more worthwhile to crop and resize with editing software.

Regarding your 500mm lens - have you tried presetting the focus, and using the focus trap mode? This can be a good way to get bird and other wildlife pictures.

brian
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Old Apr 13, 2010, 2:38 AM   #7
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I have one of those Tamron 28-200mm XR Di lenses, and I was comparing it to a fixed 200mm a while ago. I noticed that the field of view wasn't the same at 200mm. I compared to another 200mm lens and then another. I realised that the long end of the Tamron was not actually 200mm at all, but more like 160-170mm.

So to put that in context, if you used a 2x converter you'd be getting something like 320-340mm, instead of 400mm, so I think the 70-300mm is probably a good option, as it's not much shorter than the Tamron with the 2x converter.
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Old Apr 13, 2010, 10:22 AM   #8
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thanks for that info. I was worried about the sharpness of the 70-300 sigma but it sounds like the X2 tc might be worse. I actually have an extension tube but its screw mount and I only have two lenses it fits on, a 500mm and a 55mm. The 55mm with the extension tube produces some nice macro shots. (its a X2 TC with no glass) It focuses about 3 inches off the lens but still doesn't get quite the magnification I'd like for a macro. I already have 2 dedicated macro lenses, but I like to play around
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Old Apr 13, 2010, 10:29 AM   #9
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Quote:
Originally Posted by dnas View Post
I have one of those Tamron 28-200mm XR Di lenses, and I was comparing it to a fixed 200mm a while ago. I noticed that the field of view wasn't the same at 200mm. I compared to another 200mm lens and then another. I realised that the long end of the Tamron was not actually 200mm at all, but more like 160-170mm.
Try it at a focus distance closer to infinity (focus on something further away). ;-)

IOW, it's probably the focus distance causing what you're seeing when comparing 200mm lenses.

Effective focal length with a number of lens designs will change with focus distance. The focal length range in the specs assumes infinity focus.
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Old Apr 13, 2010, 3:45 PM   #10
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Jim - that's very interesting. I was taking some comparison pictures with a prime 300mm lens and a 55-300 lens and was surprised that the field of view was different. The object I was focusing on wasn't particularly close (well beyond minimum range) but not close to infinity. I'll have to try it again at further distances, to see if that makes a difference. Thanks for the information!
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