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08-20-2009, 08:24 AM   #16
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QuoteOriginally posted by Ben_Edict Quote
I see your arguments BUT I think the 1.7x AF-adapter may be the colourtful culprit. It introduces severe CAs, when attached to the 500/4.5 too - which the "real" Pentax tcs do not.
perhaps but it will also amplify the CA from the lens, and as I said, I had a chance to try the 60B with my TC and CA was much worse than the 300F4. At least that is what I saw on my camera with both lenses
QuoteQuote:
The 60B has sure some CAs, but not more, than most other lenses of that fl. When used with the correct filters (the internal one and the front filter) CAs are even less obtrusive, as these filters seem to be part of the lens' computation.
Keep in mind that the intent of using the 60B or any 300mm F2.8 would be to combine it with one of my TCs for additional length. Therefore a lens that works well with the TC is paramount. As I said earlier, the 60B in my experience was not as good as I had expected, when used with the TC. I have thought about this long and hard, and for the moment, have decided to pass on this option, especially considering the K7 performance at higher ISO.
QuoteQuote:
But obviously a FA 300/2.8 would be a much better choice...

Ben
I can't argue with this last point. I could possible consider as well an A 300F2.8 and use my 1.7X but I would have to try it first.

08-20-2009, 03:17 PM   #17
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QuoteOriginally posted by Atindra Quote
Since you have Tammy, I would like to know how problematic is the AF/MF switching by ring on Tamron lens? And do we need to swtich both lens and Camera to achieve AF to MF or Vice versa?

Atindra
A little late with this reply, sorry.
Yes, you have to pull the lens and switch the camera both to MF for you to have MF control of the lens, otherwise the lens would still be engaged with the screw-drive.
08-20-2009, 09:22 PM   #18
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QuoteOriginally posted by Ash Quote
A little late with this reply, sorry.
Yes, you have to pull the lens and switch the camera both to MF for you to have MF control of the lens, otherwise the lens would still be engaged with the screw-drive.
Thanks ASh for the info.

Atindra
08-20-2009, 09:37 PM   #19
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Thank you Ben, Lowell and Jodokast for lively and informative discussion.

The idea of buying 70-200 f/2.8 is due to several reasons,
(i) Its fast and great IQ
(ii)Can be fitted with TC with relatively less IQ loss.
and the third reason is personal one, I am making a lens buying or sort of gear upgrade roadmap for myself and this lens fits there.

My plan is to get DA 17-70 f/4 (or its sigma equivalent), 70-200 f/2.8 (Sigma or Tamron) and later to add Higher tele lens. Till then, I may use TC with 70-200 f/2.8 atleast to reach 300mm.
The reason I am not going for Sigma versions of XXX-500mm zoom lens is, they are heavy and not very easy to carry and I like to travel as light as possible.
Prime-Tele lenses are of great IQ but they are too specific and may not be useful for certain situations.

So overall I am thinking 70-200mm f/2.8 with 1.4x or 1.7x TC could be a work around with marginal IQ loss and keeping weight comparatively low.

Atindra

08-20-2009, 10:03 PM   #20
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Atindra, the 70-200s are in the order of 1.2kgs, the Sigma 135-400 also 1.2kgs, the Sigma 170-500 1.3kgs, the Sigma 120-400 1.7kgs, and the Bigma (Sigma 50-500) 1.8kgs.

So from these, there's no weight difference between the 70-200s and the 135-400 or even the 170-500. The latter lenses will save you from having to also add a TC, if what you're getting the lens primarily for is the 300-500mm focal lengths.
08-20-2009, 10:29 PM   #21
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QuoteOriginally posted by Ash Quote
Atindra, the 70-200s are in the order of 1.2kgs, the Sigma 135-400 also 1.2kgs, the Sigma 170-500 1.3kgs, the Sigma 120-400 1.7kgs, and the Bigma (Sigma 50-500) 1.8kgs.

So from these, there's no weight difference between the 70-200s and the 135-400 or even the 170-500. The latter lenses will save you from having to also add a TC, if what you're getting the lens primarily for is the 300-500mm focal lengths.
Thanks for pointing it out. I might have to have a look at it afresh.

Atindra
08-20-2009, 10:33 PM   #22
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Also be weary that the 135-400 and 170-500 lenses have smaller wide open apertures.
And even with a 2x TC, you'd only get to 400mm on a 70-200, but with significant loss of sharpness as well...

Really depends on what FL you will want to use most often and what lighting conditions you're mainly going to be shooting in.
08-21-2009, 10:19 AM   #23
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QuoteOriginally posted by Ash Quote
And even with a 2x TC, you'd only get to 400mm on a 70-200, but with significant loss of sharpness as well...
I would have to argue this point, as would some others like me who have used the Sigma APO 70-200 F2.8 EX and had excellent results with a 2X TC. See one of my previous posts for examples.

I will admit, however, that not all TCs are created equal and not all lenses perform well with a TC, but the sigma lenses designed to use the sigma TCs, in my opinion, perform very well indeed.

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