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12-11-2007, 12:27 PM   #1
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Wishing for a "Fast Lens"

I am an amatuer photographer at best, and am a happy owner of a K100 with the kit lens as well as a couple sigma lenses from my old Pentax film SLR.

A couple of days ago, I stopped by the local camera dealer, who showed me the DA* 50-135 F2.8. For curiosity, I put it on my camera and looked to see what shutter speed I could take it to, and saw that in the store with existing lighting, it could handle a 1/1000 shutter speed. I put on my Pentax kit lens and my sigma 300mm lens, and could only handle a 1/30 shutter speed.

1/30 to 1/1000 - what a difference! I do sometimes shoot inside sporting events, and sometimes just do not have enough light to take it to the needed shutter speed for crisp pictures.

I see posts about F2.8 lenses, including ones not available for Pentax as of yet.

The challenge is that I really could use more zoom than 135mm (300mm would be best). At the same time, as an amatuer, it is hard for me to justify spending many dollars for a lens!

I also understand that the K100 does not make use of all the DA* features. Other than it being more quiet on the K10 or K100 Super, what else would I be missing.

After all the above, any comments or suggestions regarding a faster lens for indoor action pictures?

12-11-2007, 02:19 PM   #2
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Something is off in your math, or in your understanding of how shutter speed and aperture work. f/2.8 is two stops faster than the f/5.6 of your kit lens (and most likely your 300mm lens), so assuming the same lighting/framing/ISO, the DA* would give you 1/1000 (@f/2.8) and your lenses would give you 1/250s (@f/5.6). You must have had the ISO set fairly high to even get 1/1000. Heck, that store must have been lit fairly well to get 1/1000 even at ISO3200. I have NO idea how you would go from 1/1000s to 1/30s...

When I think low light, I'm often at f/2.0, 1/30s, ISO1000 (using one of my fast prime lenses)

Also, to get f/2.8 @ 300mm, you're looking in the neighborhood of $3K, so keep that in mind.

I suggest you pick up a book or two on basic photography to learn how all this stuff works and then re-visit picking up some fast lenses. You might find that f/2.8 isn't fast enough for what you need to do (hint - It isn't nearly fast enough for just plain old people hanging out inside at night with regular room lighting and no flash ) That's where fast f/2 or f/1.4 prime lenses come in.

Good luck!
12-11-2007, 02:20 PM   #3
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Or buy a flash
12-11-2007, 02:22 PM   #4
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Here's a thread with some good information - https://www.pentaxforums.com/forums/pentax-dslr-discussion/11127-k100d-outside-action-pics.html



12-11-2007, 02:33 PM   #5
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I agree, that the math looks a little off, your shutter speed changed by 5 stops, but your maximum aperture on your lens only changed by 2 stops. What mode were you shooting in? Where you using one of the auto settings, or were you using one of the priority/manual settings? If you were using one of the auto settings that would explain things quite a bit, especially since those auto settings often set your ISO pretty high to keep the shutter speeds faster.
12-11-2007, 02:51 PM   #6
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I wonder if it was perhaps 1/100 shutter speed. That's about 2 stops faster than 1/30.

Or maybe he tried the kit lens first and it was stopped down a bit, then put on the DA* @ 2.8.
12-11-2007, 04:06 PM   #7
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QuoteOriginally posted by krs Quote
After all the above, any comments or suggestions regarding a faster lens for indoor action pictures?
If you're hesitant to buy the DA* 50-135, then old primes/zooms are the way to go. The DA* is priced low enough as it is, compared to the fast AF zooms going on eBay right now.

Of course, you'd have to make yourself more comfortable to metering with old lenses (it's not that hard), as well as focusing quickly/prefocusing if you're wanting to do action photos. It takes some learning, but it can be done.

If you don't fancy that, then maybe you could consider waiting for the Tamron 70-200 2.8 to come out sometime next year. In the meantime, start saving money for that lens. I'm guessing it won't be cheaper than the DA*. The Sigma version is at $890 as it is.
12-11-2007, 07:18 PM   #8
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Come to think of it, I think the DA* lens was on the shop K100 camera, and I tried my lenses on my K100, and I don't recall what their ISO speed was on. Mine was on ISO 400.

I am quite sure it 1/1000 in terms of speed, although I see your point regarding stops...

I do have a reasonable external flash, but that is sometimes frowned on in different sporting events, and sometimes you still run into distance issues.

12-11-2007, 07:25 PM   #9
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Interestingly enough, I was the individual that started the thread on the outside action pics! I also did by the book from Peterson on "Understanding Exposure" - and found it very useful (not that I am ready to write my own yet)!

When I was playing with the DA*, was set the camera in AV mode and opened the lens up (F2.8 in the case of the DA*), as far as I could in the case of the other lenses.
12-11-2007, 07:30 PM   #10
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You can occasionally find relatively fast manual focus primes for affordable prices.
But you'll have to shop around for them.
12-11-2007, 07:36 PM   #11
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QuoteOriginally posted by egordon99 Quote
Or buy a flash
12-11-2007, 10:47 PM   #12
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A flash cannot replace the 3D feel you will get from a fast lens. Flash invariably flatten everything mercilessly in candid situation. My most favorite lens is the try-and-true 50mm f1.4. Fantastic results for a good price.
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