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Forum: Pentax SLR Lens Discussion
10-10-2010, 06:27 AM
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Your TZ1 is the equivalent of 35-350mm for a full frame 35mm image.
At the long end the lens is f7.1 and (according to dpreview) iso 200 is about as high as you'd acceptably go for prints. They say the sensor is noisy and the NR loses detail above iso 200. Your opinion may differ of course, that OK.
With a Pentax APS sensor this would mean a lens of 23 - 230mm would give you the same image view.
Your 18-55 f3.5-5.6 kit lens is already wider than your TZ1 and if you go for a zoom up to 300 then this extends your reach in comparison to the TZ1.
There are a lot of threads here comparing Pentax 55-300, Sigma 70-300, Tamron 70-300 and others, and the general consensus in Pentaxforums at least is the 55-300 wins every time.
The DA55-300 is more expensive but there is a DA-L version if you can get it which is optically the same as the DA and comparable in price to the other two.
These reasonably economical zooms are all f4 - 5.8 at the long end. ie are about a stop faster than your TZ1.
Your K-x has excellent high ISO performance, better than the K-7 and is usable at 1600 or even 3200 with good quality. This performance gives you 3-4 stops of speed advantage beyond your TZ1. (and a couple better than the K-7 as well).
As "Rondec" mentions, the only common f2.8 telephoto zoom lenses for Pentax are Sigma & Tamron 70-200 f2.8, both of which weigh 1.2kg and cost 900euro and have less reach.
These are good for indoor sports with artificial light and for shallow d.o.f if maybe you wanted to isolate the action in a football game and have other players and the crowd smoothed out of focus.
For outdoors even in overcast weather you may be fine with a slower lens and using higher iso on your K-x.
For example, a really heavy overcast with subjects is shadow will be about say EV11.
Using f8 and ISO set to 1600 this gives you a shutter of 1/500. Fast enough?
I have a DA55-300 and really like it. I haven't shot much sports action and don't claim to be any good, but took the shot below at a track day where I got to ride in the passenger seat of one of these for a couple of laps. (It was 5 minutes action, 6 hours waiting around but well worth it).
The conditions were overcast (measured EV13) settings are ISO 400, f6.3 at 300mm, shutter 1/1000.
It was taken at 300mm but has been cropped to the equivalent of a 600mm view. Jpeg straight from the K-7.
The car is doing about 170km/hr. Not bad for a "slow" lens i thought.
BTW: This car/driver was leading for most of the Bathurst 1000km V8 Supercar race here today :D but then took a penalty and finshed 7th :mad:
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