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05-30-2007, 07:29 AM   #1
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Macro Lens choice

I am getting ready to pull the plug on a Macro lens purchase. Have reviewed the posts here and reviews of the three lenses I am considering. Would like your guidance to throw into the process.

My intended use is going to be closeups of flowers, insects, and other interesting or beautiful objects.

My biggest area of confusion is 50mm vs 70mm vs 100mm. I am looking at the Pentax 50 and 100mm lenses and the Sigma 70mm EX lens. I own a Pentax K10D. What are the advantages of one focal length over the other and keep in mind budget is a consideration as I only intend to have one macro lens. This lens will round out a kit that includes a Tamron 18-200 and a Pentax 35mm lens. I also intend to purchase a tripod but that is another issue.

Your thoughts are welcomed and thanks in advance.

05-30-2007, 08:02 AM   #2
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100mm allows you to to keep more distance to the subject at the same magnification, so that's what I would recommend. As an example the distance to the subject at 1:1 magnification with a 100mm is 31cm, and just 23cm with a 50mm lens.

The wider the max. aperture the easier it is to focus. So an f/2.8 lens is easier to focus then an f/4.

Autofocus is less important. You most often focus by moving the camera back and forth anyway when doing macro.

Hope this helps.
05-30-2007, 03:25 PM   #3
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Thanks for the response Ole - I am leaning to the Pentax 100mm and you have provided valuable info in the process to spend my hard eaned dollars.
05-30-2007, 06:56 PM   #4
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This helps me out greatly too! I was just trying to decide on the 50 or the 100. I just bought the 100 after reading this post (along with the 540 flash) Yippee! I can't wait for the UPS man now!

05-30-2007, 07:53 PM   #5
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Glad that I could help!
I'm very satisfied with my D FA 100mm!!

You may want to read this thread so that the autofocsing behavior of this lens doesn't surprise you:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/6960-question-...html#post57009
05-31-2007, 05:21 AM   #6
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all of the third party lenses are just as good too. i've got a vivitar 105mm f2.5 and it'll go up against any modern lens. it has the A setting(not important, but nice) and no AF, which isn't important either. if $$$ are scarce you can pick up these other lenses fot 1/3-1/2 of the modern lenses. here's a couple of recent shots.



05-31-2007, 06:41 AM   #7
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Thanks Roy and those are some great shots.
05-31-2007, 08:37 AM   #8
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QuoteOriginally posted by Ole Quote
100mm allows you to to keep more distance to the subject at the same magnification, so that's what I would recommend. As an example the distance to the subject at 1:1 magnification with a 100mm is 31cm, and just 23cm with a 50mm lens.

The wider the max. aperture the easier it is to focus. So an f/2.8 lens is easier to focus then an f/4.

Autofocus is less important. You most often focus by moving the camera back and forth anyway when doing macro.

Hope this helps.
How about DOF? For the same apeture, is DOF reduced for 100mm compared to 50mm?

05-31-2007, 08:45 AM   #9
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DOF should be a little more on the 50mm. for real macros you really need to shoot at min. f11. i shoot at f16 99% of the time. i also use difussed flash 90% of the time, usually off camera.
06-01-2007, 01:30 AM   #10
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I love my DFA 100 mm macro too





06-01-2007, 02:36 AM   #11
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QuoteOriginally posted by roy Quote
DOF should be a little more on the 50mm. for real macros you really need to shoot at min. f11. i shoot at f16 99% of the time. i also use difussed flash 90% of the time, usually off camera.

for the 100mm macro resolution drops off significantly at f22 -

Pentax SMC-D FA 100mm f/2.8 macro - Photozone Review / Lab Test Report
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