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03-26-2007, 06:01 AM   #1
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100-300 , 50-500, TC, tele - please help

hi,

i want to buy a tele-zoom for my K100D.
i would like as much zoom as possible (animals & birds)
and i want to have fast focus !

important note, if AF or SR will not work in some cases, please point it, because i like to have them.

another important note, i looked at my pictures, and with the 50-200 i am using almost just the 200mm !!!
so this is the reason i want bigger zoom

currently i have 18-55 & 50-200 & TC tamron 1.4x

my thoughts were -

Sigma 100-300 F4,
this way i will have 100-300 with the best quality
with the TC 1.4 i will have a very good quality at 420mm F5.6 (i assume that TC will lower the quality),
people say that the SR will not work so good, because the camera doesn't know that i attached TC.

and now... lets talk about bigma (50-500 F4.0-6.3)
it's heavy ! i am afraid from it !
but 50-500mm... tempting

but if you will say that 100-300 is so much better, and with TC, it will still be better, then there is no issue.

please help...

thanks !

Shay

03-26-2007, 07:00 AM   #2
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QuoteOriginally posted by shayt Quote
hi,

i want to buy a tele-zoom for my K100D.
i would like as much zoom as possible (animals & birds)
and i want to have fast focus !

important note, if AF or SR will not work in some cases, please point it, because i like to have them.

another important note, i looked at my pictures, and with the 50-200 i am using almost just the 200mm !!!
so this is the reason i want bigger zoom

currently i have 18-55 & 50-200 & TC tamron 1.4x

my thoughts were -

Sigma 100-300 F4,
this way i will have 100-300 with the best quality
with the TC 1.4 i will have a very good quality at 420mm F5.6 (i assume that TC will lower the quality),
people say that the SR will not work so good, because the camera doesn't know that i attached TC.
I have the Sigma EX 100-300 f4 DG lens and matching EX 1.4 tele-converter, so I can tell you how that lens works. I don't have the Sigma 50-500 so I can't offer a comparison. (I believe that Sigma used to make a slower, non-EX 100-300 that was not as good as the EX f4. I don't see it listed in the current Sigma catalog and I don't know if it is available in the Pentax mount).

I am very pleased with the image quality from the 100-300 f4, especially with the small sensor on the digital bodies. It provides sharp, contrasty images even wide open, and is at it's best at around f8-11. I can detect very little quality loss with the matched teleconverter, and I get very nice results at 420mm stopped down one stop (f5.6 indicated, effectively f8). I've never been much of a fan of third party lenses, but this Sigma surprised me. I chose it over the 50-500 because it is a bit lighter, it doesn't extend when zoomed or focused (all internal), and it is faster at longer focal lengths for a brighter viewfinder image. I also have a Pentax SMC-M* 300 f4 which is a great lens, and the Sigma is very nearly as good. The M* is a bit sharper and has a bit more contrast, but the Sigma is much easier to work with on a digital body.

This lens is big and heavy. It can be hand-held but the best results at longer focal lengths will require some support. But with my K10D body and SR, I can get pretty decent results at rather low shutter speeds. I haven't tried to hand-hold the 100-300+converter+K10D.

As for auto-focus speeds, I have spent considerable time testing this and comparing the 100-300 in the Pentax mount with other systems. I use this lens for action/sports photography at my son's soccer games. I was using my manual focus Pentax M*300 f4 but it was very hard to maintain sharp focus with the kids running in unpredictable directions, and I needed the flexibility of the zoom (since I can't run as fast as the kids). Using the Sigma 100-300 on my *ist DL body, the AF speed is barely acceptable without the converter, and too slow with the converter. Using my K10D body, AF speed is very good without the converter and barely acceptable with the converter. The converter results in a longer focal length, one stop of light loss, and additional mechanical drag, all of which slow the AF.

I compared my Sigma to both the Canon 100-400 f4.5-5.6L with a Rebel XTi body and a Nikon 80-400 f4.5-5.6 VR with a D80 body. These seem like the most reasonable alternatives in the other brands. The Nikon 80-400 is rather slow to focus, due to the fact that it lacks an in-lens motor. I would say that my Sigma 100-300+K10D (w/o converter) focuses as fast or faster than the Nikon combination. The Canon lens is quite fast to focus even to 400mm and is a bit faster than the Sigma 100-300+K10D (w/o converter), but not so much as to make much of a difference in normal use. But my Sigma with the converter is slowest to focus.

I will let you draw your own conclusions from my experience. AF speed is less critical for wildlife shots than sports shots, and I would have no hesitations to use the teleconverter with wildlife shots. But if you want the fastest AF speed then you might want to wait for Pentax lenses with the in-lens motors. Of course, you will need a new body to take advantage of this.

Last edited by GaryML; 03-27-2007 at 12:42 PM. Reason: fixed typo
03-26-2007, 07:06 AM   #3
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Thanks !

thank you very much for the answer.

Shay
03-26-2007, 05:41 PM   #4
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Shay.
I think Gary pretty much nailed the capabilities of this lens. I bought one a month or so ago and have found it to be everything he said it is.

The sharpness of the lens is quite excellent, the color rendition slightly cooler than Pentax lenses in general, but the speed of AF even with the screwmount inboard motor is fairly quick. The lens is usable and fairly sharp wide open and does improve somewhat over the next few stops.

I find the lens comfortable to handhold and not as heavy to deal with as some complain about.

If you are looking for in depth comment on the lens and its rating you can check out Fred Miranda's reviews site. They have lots of comments on this lens.

It travels easier than the 50-500 and it reamains AF with 1.4 extender which is dedicated to the EX DG series of lenses. The 2x extender is not AF compatible but should produce quality images in conjunction with the lens.

Stephen


Last edited by SCGushue; 03-26-2007 at 05:43 PM. Reason: correction
03-27-2007, 03:09 AM   #5
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some additional info about 100-300/4 is here:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/3851-sigma-100...-f4-5-6-a.html
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