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06-06-2008, 09:55 AM   #1
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70-300mm F3.2-4.5

I started a discussion about this lens a while ago on DPreview:
Why no 70-300mm F3.5-4.5?: Pentax SLR Talk Forum: Digital Photography Review

I'm the kind of guy that likes to walk around with reasonably light and hand holdable gear looking for scenery, patterns, compositions that sort of thing. If I walk with my brother he is always the one saying: you see that rabbit, see that bird or anything else that escapes my attention or out distances the sharpness of my eye. So very far range (300mm+) is not really my priority however when the opportunity does arise I would hate to think that I brought a pretty expensive DSLR with a telelens and not be able to get a decent close up shot of good quality.

For image quality sake I'm willing to split up my most used focal range (say 17-300mm) up with two hand holdable yet reasonably bright lenses (17-70mm and 70-300mm). On those occasions that I do want to shoot more than 300mm I like the option of adding a 1.4x TC and retain decent quality and aperture. I don't really like any xxx-400mm lens, because those are generally heavier and I don't really fancy compromising (aperture, wide end) my most used range (under 300mm) because of an occasional 300mm+ shot.

For this reason I would like a 70-300mm F3.2-4.5 lens with the following specification:

- Focal length: 70-300mm
- Max. Aperture: F3.2-4.5
- Size: 80x150mm, filter 72mm
- Weight: 850-1000gr
- Constr: Outer zooming
- MSRP: 500-750

It would be outer zooming to keep cost, size and weight down, however it's optical performance would have to stay close to the likes of the FA* 300mm F4.5 and Sigma 100-300mm F4 to remain usable with a 1.4x TC. The problem I have with the latter is cost, size and weight as well a narrow wide end. A 70-200mm F2.8 with a 1.4x and/or 2.0x TC is another option although much more expensive and the zoom range would be somewhat narrow. Then there is Pentax own 60-250mm, which does look interesting. However I do expect it to be quite large and expensive with it's inner zooming design and it would need a 1.7x TC to get similar reach.

Use of a 1.4x TC with the proposed 70-300mm lens would give a 98-420mm F4.5-6.3, still a very usable focal and aperture range in my view. Now I don't see anything like this coming from Pentax themselves, but for instance Tamron doesn't really have anything like it in it's range. To me this would be close to the ideal lens:

- I wouldn't go bankrupt when buying it.
- Still relatively light and compact, so I can easily walk around with it and shoot it handheld.
- Very usable aperture throughout it's range.
- Pretty good sharpness (needed to be usable with a TC).
- Very nice 98-420mm F4.5-6.3 when used with a 1.4x TC.


Anyone else shoots more or less the way I do and like a lens like that?


Last edited by CSpronken; 06-06-2008 at 05:18 PM.
06-06-2008, 05:21 PM   #2
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I wouldn't mind one like that either, simply for the reason that I could put a TC on it and have it not be too slow. I figured that between the crop factor of the camera itself and a 1.5x TC, I could go out to an equivalent 625mm.

I've thought about going ahead and getting a 1.5x TC from Adorama and trying it on my 55-300 to see how it would work. If my calculation is correct, the maximum aperture on the long end would jump from 5.8 to 8.7. If I'm shooting in broad daylight, I wouldn't think that would be a big deal, as I normally shoot with at least f8 or f11, if not smaller without a TC.
K15AFDGP Kenko Teleplus "DG" 1.5x AF Teleconverter for Pentax AF

At some point, I might see about picking up either a 70-200/2.8 or the 60-250/4, either of which will work well with a TC, but before that happens, I've got bigger fish to fry in terms of lens purchases.

Heather
06-06-2008, 11:09 PM   #3
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About the closest you will get is getting the Sigma 70-200mm F/2.8 (or the upcoming Tamron of same specs) ... and using the x1.4 TC.

I have a Tamron x1.4TC already ... I am just waiting for the Tamron 70-200mm F/2.8 now to complement it.
06-07-2008, 03:03 AM   #4
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Original Poster
QuoteOriginally posted by hwblanks Quote
I wouldn't mind one like that either, simply for the reason that I could put a TC on it and have it not be too slow. I figured that between the crop factor of the camera itself and a 1.5x TC, I could go out to an equivalent 625mm.
Yeah 300mm x 1.53 x 1.4 or 1.5 would be plenty for me as well.


QuoteOriginally posted by hwblanks Quote
I've thought about going ahead and getting a 1.5x TC from Adorama and trying it on my 55-300 to see how it would work. If my calculation is correct, the maximum aperture on the long end would jump from 5.8 to 8.7. If I'm shooting in broad daylight, I wouldn't think that would be a big deal, as I normally shoot with at least f8 or f11, if not smaller without a TC.
K15AFDGP Kenko Teleplus "DG" 1.5x AF Teleconverter for Pentax AF
I think forummember Richardday is about to test a 55-300mm with one of his TC, I reckon his experience is gonna be interesting. I think for moving objects in dim conditions is gonna be hard.

One thing to think about though (forgot about it myself) is that the AF uses the widest aperture even if you shoot at F8 or F11. What I want to say is that AF with a max. aperture F8.7 is not going to be as good as using F11 on a lens with max aperture F5.6 for instance.


QuoteOriginally posted by hwblanks Quote
At some point, I might see about picking up either a 70-200/2.8 or the 60-250/4, either of which will work well with a TC, but before that happens, I've got bigger fish to fry in terms of lens purchases.

Heather

QuoteOriginally posted by Mechan1k Quote
About the closest you will get is getting the Sigma 70-200mm F/2.8 (or the upcoming Tamron of same specs) ... and using the x1.4 TC.

Yeah that might work for me as well, just that they're larger heavier and more expensive, so that makes them less attractive for me.

QuoteOriginally posted by Mechan1k Quote
I have a Tamron x1.4TC already ... I am just waiting for the Tamron 70-200mm F/2.8 now to complement it.
Looking forward to hearing how well that combo works for you.


Last edited by CSpronken; 06-07-2008 at 02:54 PM.
06-07-2008, 02:25 PM   #5
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I now have to play the waiting game .. it might still be a while till the Tamron comes in the Pentax mount yet.
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