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12-30-2010, 06:04 AM   #1
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First question

Hi, I'm new to the forum. Just got a kx for Christmas...(gotta love the daughters!). I had a Pentax years ago and loved the quality of photos. I am coming from a superzoom...(lumix FZ7) and got so used to the zoom, now I am needing my zoom fix! I am considering a Tamron 70 - 300 over Sigma just because of reviews. I want to get the macro feature because...well....because I enjoy macro! Don't have the money yet to invest too much at one time and really want to go easy as I don't want to have a bunch of $$ in lenses I won't use much....yet. Any advice? I will be shooting some low light, do alot of landscapes and want versatility. Thanks in advance!

12-30-2010, 09:12 AM   #2
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Hi cjbroadwell,

I think that this is a good choice. The Sigma 70-300 is usually also mentioned in this general price class, and though it offers a bit better chromatic aberration and purple fringing control, the Tamron's 1:2 max magnification ratio does trump the Sigma's 1:4.

From a telephoto Image Quality standpoint, the Pentax DA 55-300 seems to be a better lens, but it's in a different price category.

Congrats on your new Kx. It's a great camera and I think that with the telephoto zoom, you'll find it a definite step up from your FZ7. About 5 years ago, I bought an *ist DS as my first DSLR, and some 5 bodies and 20+ lenses later, I couldn't be happier that I made the switch.

The high ISO capabilities of the Kx sensor will give you the ability to use this lens in relatively low light despite its relatively slow max aperture. The 1.5x "crop factor will give you comparable reach (Field of View) to what you had with your FZ7. 70-300mm will have a FOV equivalent of 105-450mm in 35mm film terms, and your FZ7 has a 36-435mm equivalent FOV in the same format.

I noticed your other post, so I'll try to answer this here.

Most consumer camera lenses these days refer to a "35mm equivalent" for focal length. This is a convention they've adopted to give people a constant to compare to to show approximately what you'll see in the viewfinder with any given lens. 35mm has been chosen since this is the most common film format for the past 50 years.

In Pentax's case, the sensors they use are roughly 24mmx16mm. 35mm film is roughly 36mmx24mm. The sensor size they use is generically called APS-C, and since the DLSRs use the same lenses as the 35mm film cameras, the sensor frame captures an image that is essentially a crop of the film frame. Since it's about 2/3 the size of the film frame in each linear direction, the image captured appears to be about 1.5x magnified, so the "crop factor" is 1.5x -- any lens that you can use on a Pentax DSLR will have a FOV that is 1.5x smaller, and the image will appear to be 1.5x bigger in relation to the viewfinder frame.

Panasonic also used a crop factor to get their 35mm equivalent focal lengths that they advertise. The actual sensor size is 5.76 x 4.29 mm (let's round it off to @ 6x4.5mm) so it's about 1/4 the size of the APS-C sensor linearly, and 1/6 compared to a 35mm film frame, so the "crop factor" would be @ 6x. The actual focal length range is 6mm-72mm, so the equivalent is @ 36-432mm. This is useful to compare to what you're used to , but IMO, people should get over it and just refer to actual FL, once theyve gotten used to the FOV of their camera. Crop factor just confuses things.

What I've done is to adopt APS-C as my personal standard, and I know what a 300mm lens looks like in the VF, so I just look at it as a 300mm lens and forget the "crop factor" since how it looks in a 35mm film camera no longer has any meaning to me though I shot 35mm film since the late '60's. I haven't looked through a 35mm VF for over 6 years, and couldn't care less since I exclusively use an APS-C DSLR.

Scott

Last edited by snostorm; 12-30-2010 at 09:21 AM.
12-30-2010, 10:12 AM   #3
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Thanks for taking the time for a very informative lesson!
12-30-2010, 10:53 AM   #4
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Welcome aboard!

I can't give you a direct compare but for the money, the Tamron is quite a nice lens. It gets a little soft at 300mm but nothing that cannot be fixed up. The biggest complaint about the lens is the purple fringing, especially wide open in certain situations. Again, simple fix but it may frustrate you at times. For the record, I can make just about any lens Purple Fringe, including my $1200 FA*85 (to a small degree).

The Tamron was the first zoom I ever bought but I didn't use it very much so I sold it last fall. Every camera I put it on however, the focus was lightning fast (relative term) and accurate. The 1:2 'macro' is probably it's best feature if that's your photographic joy. Note that the macro is only available from 180mm to 300mm however.

A few from mine.

Show Tamron - a set on Flickr



12-30-2010, 11:01 AM   #5
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Hi CJB and welcome. If you don't mind manual focusing I'd recommend the Pentax A 70-210 F4.0. It also has a "macro" feature. I never owned the Tamron you are looking at, but I can say that the Pentax A is much much better than the Pentax DA 55-200.

NaCl(just my 2 cents and worth all of that)H2O
12-30-2010, 11:23 AM   #6
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Here is an example of what the Tamron can do. I like this lens a lot and for the $ it is pretty hard to beat. Like others have stated the CA is pretty bad at times but can be fixed.

12-30-2010, 04:21 PM   #7
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QuoteOriginally posted by cjbroadwell Quote
Hi, I'm new to the forum. Just got a kx for Christmas...(gotta love the daughters!). I had a Pentax years ago and loved the quality of photos. I am coming from a superzoom...(lumix FZ7) and got so used to the zoom, now I am needing my zoom fix! I am considering a Tamron 70 - 300 over Sigma just because of reviews. I want to get the macro feature because...well....because I enjoy macro! Don't have the money yet to invest too much at one time and really want to go easy as I don't want to have a bunch of $$ in lenses I won't use much....yet. Any advice? I will be shooting some low light, do alot of landscapes and want versatility. Thanks in advance!
It is a decent budget zoom, but with f4-5.6 it is not particularly great in low light, especially if you want to stop down for image quality. The "macro" mode is good for flowers but not for really small bug details that you can get with a true macro lens.

It's inexpensive enough that it is a good start. Eventually you can sell with not too much total loss it as there is always a market for them, if you want to progress up the LBA path.
12-30-2010, 04:48 PM   #8
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QuoteOriginally posted by SpecialK Quote
It is a decent budget zoom, but with f4-5.6 it is not particularly great in low light, especially if you want to stop down for image quality. The "macro" mode is good for flowers but not for really small bug details that you can get with a true macro lens...
It's also pretty big when you attempt to use it at its highest magnification. I tested a borrowed one (Quantaray version) against a true macro, the Tamron 90mm f2.5 Adaptall-2, also 1:2 magnification. I used a $20 bill taped to a wall. The zoom is not great at larger apertures, but unless your target is really flat, you can't really get decent depth of field at larger apertures.

http://home.comcast.net/~davidstewart298/Lenstests/300mmMacroCenters.jpg

http://home.comcast.net/~davidstewart298/Lenstests/300mmMacroCorners.jpg

I almost have bought one of these a couple of times because my other 300mm lens is the SMC Pentax 300mm f4 prime, which has no close-up ability at all.


Last edited by Just1MoreDave; 12-30-2010 at 04:56 PM.
01-05-2011, 02:23 PM   #9
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I have the lens, and it's good at autofocus - it's always dead-on and fast. It's purple fringe above 200 in high contrast situations - very predictable. I'll shoot a couple around 180 then zoom out and take my chances. I'm looking to upgrade soon. It's a question of money, really....for the $80 or so I got it for, it's been a good lens.
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