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Old Apr 28, 2006, 10:59 AM   #1
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Hey everyone - i'm a newbie here and I'm really sorry for probably bringing up another one of these damn threads about which lens to buy!

I've had my DS for 8 months now or so and I love it, but I am thinking of swapping lenses. I currently have the Sigma 18-50 lens and the Sigma 55-200 that came with the camera (I'm in Aus btw which probably won't change much!)

Anyway - I was wanting to change because I do a fair bit of travelling and the changing of the lenses gets annoying, and I don't want to get one of those 18-200 lenses because I hear they arent that great. The lenses I am looking at however are the Sigma 18-125 (I've heard so many good things about that!), and the Pentax 100-300 f/4.7-5.8, as well as the possibility of the Sigma 70-300 f/4-5.6.

Can you please give your opinions on which lens would be better? I am pretty much decided on the 18-125, but am unsure of the other two.
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Old Apr 28, 2006, 12:44 PM   #2
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Ill give you another option. the Penatx FA28-105 F3.2--4.5 . I leave it on my Camera all the time. As for the Sigma 70-300 great lense. I love it!!
If you check for the thread 'Sigma 70-300MM lense, i have posted Some pictures with It. I cannot speak about the others you mentioned.

BK
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Old Apr 28, 2006, 1:05 PM   #3
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Patang

I own the the Pentax FA100-300 f/4.7-5.8 which I got for a very good price. I have used it for quite a few of the pictures I have posted here. More information can be found here: http://www.stevesforums.com/forums/v...mp;forum_id=80 It has a plastic lens mount but I do not see that as a problem since it is very light weight for the range (great for travelling or backpacking).

I do not own the Sigma but I have used the Canon mount version on a 20D. It is a nice lens but not a great lens.My newest acquisition is a 24-135mm Sigma f2.8-4.5 which is big and heavy, but offers an excellent range and good maximum apertures. This zoom range covers at least 90% of my shooting, the 18-125mm is much smaller and lighter, and just as fast as the Pentax kit lens, so it may be an excellent companion to the 100-300mm Pentax.

Any lens is a compromise. If, like me, your budget is somewhat limited, the Sigma would not be a bad choice for a travel lens and the Pentax Fa 100-300mm f4.7-5.8 (not its bigger heavier power zoom brother) would make an excellent long telephoto. Faster lenses are very heavy and very expensive so I get what I can find in my price range.

Ira
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Old Apr 28, 2006, 3:50 PM   #4
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I have the Sigma 18-125 as my everyday lens and it is very good. It offers good auto focus time and not too heavy. I compare it well with the kit lens in its range. I too am looking for a longer range lens but I want something that will still have the ability to open up wide enough when I need it. The Pentax 50-200 has been a consideration but I'm just not sure it will satisfy my needs. The Sigma 28-200 might though. That lens is available at a reasonable price if you shop around. As for the 18-125 I think you would like it.
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Old Apr 29, 2006, 11:25 PM   #5
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hey everyone - thanks for the replies! Just another question in regards to the pentax 100-300, because it is such a big zoom lens, is it necessary to use a tripod for zoom between 200-300? or just a the very end of the zoom range?
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Old Apr 30, 2006, 9:00 AM   #6
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Patang

At such long focal lengths it is always a good idea to use a tripod but the 100-300mm Pentax is so light weight that it can be hand held easily if the shutter speed is fast enough (ie. 1/focal length ). The gull pictures in the first few posts here: http://www.stevesforums.com/forums/v...mp;forum_id=80 were all taken with that lens, hand held at 300mm, and I am not a particularly steady person.

The light weight of this lens also means you do not need a super heavy duty tripod.

Some will argue that the mass of a heavier lens makes it easier to hold steady, but my experience with this lens is that it is comfortable to hold and not tiring.

Ira
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Old Apr 30, 2006, 10:03 AM   #7
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Ira,

You are a veritable fountain of knowledge! It must get quite annoying having people like me come up and ask questions that have been asked hundreds of times before! All the photos here are fantastic and I'm feeling daunted just looking at them all!
And what do you teach? I saw in one of the threads you had a photo of your classroom.

Pat
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Old Apr 30, 2006, 4:57 PM   #8
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Patang,

I am a science teacher in high school. You can check out our photo club at http://www.k12.nf.ca/gc/photoclubweb/photoclub.htm .

Thank you for the kind words, I don't mind answering questions and I always try to get the facts straight, it goes with the job.

Ira
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Old Apr 30, 2006, 9:07 PM   #9
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I have just come across the sigma 100-300mm DL f/4.5-6.7 when trawling through ebay and the like, and I am wondering if anyone here as used it as a lens, or what the comparison would be for the pentax 100-300mm SMCP-FA f/4.7-5.8.
Ira loves his pentax, but has anyone used the sigma on a DS?

Also, this may seem a stupid question, so forgive my ignorance, but because lens for digital cameras come out with more range when attached to regular SLRs, ie 75-300 becomes 100-450 essentially, what does that mean when you use the lenses I've just mentioned on a digital? Is the focal length less or the same?



:?

Pat
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Old Apr 30, 2006, 9:15 PM   #10
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Due to the 1.5X crop factor of the APS-C sensor used in all Pentax DSLRs, all lens focal lengths must be multiplied by 1.5 in order to get the equivalent to a 35mm frame. Therefore the 18-55mm DA (digital) kit lens is a 27- 82.5mm equivalent, the 100-300mm lens becomes the functional equivalent to a 150-450mm lens on a 35mm camera. ALL lenses, whether designed for digital of 35mm, must have that crop factor applied in order to compare field of view on the DSLR with a 35mm SLR.

Before anyone chimes in to correct me, let me state again that this is the effective field of view and the focal length of the lens does not actually change.

Ira
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