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11-18-2007, 07:15 AM   #1
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Starting Lenses

Okay, I am moving into the foray of DSLR's and am seriously considering the K10D and Nikon D70. I love the D10D's features (shake reduction and sealed body especially since I will take it hiking), but cannot find all that much about lenses.

It seems that the DA lenses don't have the 'magnification' factor that other lens/bodies do (ie. a 50mm lens on a D70 is more like a 70mm lens from a 35mm SLR), is that correct?

Looking at the pricing of the lenses, it seems that the higher-end glass is less expensive than its Canon/Nikon counterparts, but that there are no lower-end primes (like the 50/1.8 that is so sharp and cheap for Nikon/Canon), is this true? Am I just missing the cheap yet sharp primes?

Thanks for any input,
Matt


Last edited by MattWe; 11-18-2007 at 07:22 AM.
11-18-2007, 07:33 AM   #2
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The Pentax crop factor is 1.5. All DSLR other than full-frame have a crop factor. It alters the field of view and not really the magnification.

I have the 35mm f/2 and the 50mm f/1.7 and think both are great.
11-18-2007, 07:49 AM   #3
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QuoteOriginally posted by MattWe Quote
It seems that the DA lenses don't have the 'magnification' factor that other lens/bodies do (ie. a 50mm lens on a D70 is more like a 70mm lens from a 35mm SLR), is that correct?
This is false, a 50mm lens is a 50mm lens. They haven't changed the standard since the 35mm days.
What you see is just a little different, but I wouldn't worry about it unless your moving from 35mm SLR's.

You can get good glass or cheap lenses for any of the cameras, but for the most part you still get what you pay for.
The one real advantage of Pentax is you can use just about any lens ever made for a Pentax on our cameras. Although we do require adapter's for a few, so if you buy a Pentax and have any doubts on a lens please ask us here.

Have fun and good luck with your decision.
11-18-2007, 08:17 AM   #4
baw
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Starting lenses

If you have the money i'd go for the Pentax (or Tamron) 18-250.
Great lens, covering a wide range of focal lengths.
Combined with shake reduction on the K100D or K10D a pretty amazing combination imo.

After some time you get a good feel were you need ( or just want ) specialized lenses.
Wide angle like the 12-24 or tele, perhaps some primes, but you still have the 18-250 as a walkaround lens for every day use.

11-18-2007, 08:40 AM   #5
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QuoteOriginally posted by patrickt Quote
The Pentax crop factor is 1.5. All DSLR other than full-frame have a crop factor. It alters the field of view and not really the magnification.
I guess I misunderstood, I thought that the crop factor was due to the lens being full frame and the sensor being less than full frame and that the DA lenses are the same size as the sensor and there wouldn't be any crop factor. I would love for someone to explain that to me, though.

QuoteOriginally posted by little laker Quote
I wouldn't worry about it unless your moving from 35mm SLR's.
I am, although I am years removed from SLR's (sold all my equipment when I had a bunch of unexpected bills crop up) so I probably wouldn't notice the difference.

QuoteOriginally posted by baw Quote
If you have the money i'd go for the Pentax (or Tamron) 18-250.
Great lens, covering a wide range of focal lengths.
Combined with shake reduction on the K100D or K10D a pretty amazing combination imo.
Would that be better than the kit lens + the 50-200mm? The prices for both of those combos (body + 18-250 and Kit + 50-200) are only a couple hundred difference, and if the 18-250 is that much nicer of a lens, I would probably go for it.
11-19-2007, 12:59 AM   #6
baw
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Starting Lenses

QuoteQuote:
Would that be better than the kit lens + the 50-200mm? The prices for both of those combos (body + 18-250 and Kit + 50-200) are only a couple hundred difference, and if the 18-250 is that much nicer of a lens, I would probably go for it.
I've never used the 50-200, but my 18-55 is collecting dust since I got the 18-250.
Also don't underestimate the convenience of a single lens solution against 2 lenses in this case.
Have a look at this site for tests on lenses etc.
In this album 95% of the images were shot with my K100D and the Tamron 18-250.

Last edited by baw; 11-20-2007 at 12:03 AM.
11-19-2007, 04:44 AM   #7
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QuoteOriginally posted by MattWe Quote
I guess I misunderstood, I thought that the crop factor was due to the lens being full frame and the sensor being less than full frame and that the DA lenses are the same size as the sensor and there wouldn't be any crop factor. I would love for someone to explain that to me, though.
The crop factor is due to the sensor being less than full frame, not on lenses.

Let me show in Computer Science's truth table fashion
FF lens on FF sensor: no crop factor
FF lens on APS-C sensor: crop factor applies
DA lens on APS-C sensor: crop factor applies
DA lens on FF sensor: no crop factor (but iq not guaranteed outside the APS-C frame).
11-19-2007, 05:28 AM   #8
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QuoteOriginally posted by MattWe Quote
I guess I misunderstood, I thought that the crop factor was due to the lens being full frame and the sensor being less than full frame and that the DA lenses are the same size as the sensor and there wouldn't be any crop factor. I would love for someone to explain that to me, though.
Short and sweet: any 50mm lens will resolve exactly the same, no matter the intended format, when held up to your camera. (Also good to know is that the Pentax DSLRs have a sensor the same size as the Nikon D70, so a 50mm on a Pentax DSLR will look just like a 50mm on a Nikon D70.) Focal length is nothing more than a physical measurement of the distance behind the lens that light will focus. This property doesn't change when you hold it in front of different films/sensors.

The difference between systems is the size of the image circle itself. If you take a 50mm lens designed for medium format, it will cover a huge image circle - enough to completely cover the 60mm by 45mm negative. Put that same lens in front of a 35mm film camera and you only see the center 36mm by 24mm. The lens hasn't changed one bit what it is rendering, you are only in essence 'cropping' out the center portion of the image.

11-19-2007, 05:39 AM   #9
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Crop factor

I like to point people to the following Wikipedia entry to explain focal length, angle of view and crop factors: Crop factor - Wikipedia, the free encyclopedia
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