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12-11-2009, 06:13 PM   #1
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Need some help with macro questions

1 - all else being equal would 100mm macro give you a closer more detailed magnified shot than a 50mm macro?

2 - Also, it seems some macro lenses are 50mm at lets say f 2.8. Other than the faster speed, how is it any different than my K-x kit lens which can do 50mm? This has been on my mind lately any help would be appreciated

Thanks!

12-11-2009, 06:48 PM   #2
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QuoteOriginally posted by boodiespost Quote
1 - all else being equal would 100mm macro give you a closer more detailed magnified shot than a 50mm macro?
"Macro" is normally expressed in terms of "magnification ratio." It is the ratio of the size of the real object and the size of the image on sensor. For example, 1:2 means the size of the image is half the size of the real object, 1:1 means the size of the image is the same as the size of the real object.

If the 100mm macro lens and the 50mm macro lens give you the same magnification ratio, the photos have the same level of details. The main difference is that to achieve the same level of magnification ration (say, 1:1), the lens with greater focal length allows a greater distance from the sensor/film plane to the object than the lens with lesser focal length.

QuoteOriginally posted by boodiespost Quote
2 - Also, it seems some macro lenses are 50mm at lets say f 2.8. Other than the faster speed, how is it any different than my K-x kit lens which can do 50mm? This has been on my mind lately any help would be appreciated
Non-macro lenses normally have max. magnification ratio about 1:7, and min. focusing distance about 8X focal length. Zoom lenses may have max. magnification ratio up to 1:3.

Macro lenses typically have max. magnification ratio of 1:1, some 1:2. At 1:1, min. focusing distance is about 3X focal length.

Also, macro lenses have flatter field, less distortion especially at macro distances. In general, being specialized, they are manufactured with tighter QC.

Last edited by SOldBear; 12-11-2009 at 07:19 PM.
12-11-2009, 07:15 PM   #3
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thanks for the answer, i am still quite confused. so are you saying my K-x kit lens at 50mm will need at least 400mm focusing distance while a macro 50mm will need 150mm?

also, could you explain the 1:7 1:2 1:1 ratios that you mentioned? I am not quite getting it.
12-11-2009, 07:57 PM   #4
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I too had also asked a couple macro questions (specifically the ratio). Got some good answers.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/78679-macro-question.html

12-11-2009, 08:59 PM   #5
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thanks for that ^^
12-11-2009, 09:48 PM   #6
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Here's the short answer:

Macro lenses are not magic. A 50mm macro lens and the 50mm on your kit lens are *exactly* the same in almost all respects. The only difference is that the macro lens lets you focus from a short distance. That's all it does. So you can get things to look more magnified in a macro lens because you can shoot from a shorter distance; that's it. If you shot the same item from the same distance using a 50mm macro and your kit lens at 50mm, it would look exactly the same, but the kit lens can only focus within a foor or so, and a 50mm lens can focus within a an inch or two.

Magnification ratios refer to the size of the image on the actual sensor in your camera. 1:1 means an object that is 1 inch wide is reproduced 1 inch wide on your sensor. Since your ensor is 1 inch wide (more or less), that makes it easy: a 1:1 magnification allows you to to fill the frame with an object one inch wide. 1:2 magnification allows to you to fill the frame with a two inch object; 1:3 fills the frame with a three inch object, etc.

So to answer you original question: if the 50mm and 100mm macro are both 1:1, then no, the 100mm will not produce a more magnified image. But it will achieve that 1:1 magnification shooting from about 6 inches away (just a rough guess), whereas the 50mm would need you to be a only an inch or two away.
12-12-2009, 10:22 AM   #7
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i see... thanks for the indept and clear explanation.

by the way, Marc. I can't believe you live in Denver. I lived in Colorado for 17 years before I moved here to California. Where abouts do you live? I lived everywhere in those 17 years, aurora, denver, littleton, highlands ranch, boulder, thornton... Good to see a fellow coloradan ^^
12-12-2009, 10:57 AM   #8
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Following up on Marc's good info, at a 1:1 magnification, the distance from the lens to the subject is about 2 times the focal length. This is perhaps the main reason why people choose longer rather than shorter focal length lenses for macro work.

Dave in Iowa

12-12-2009, 11:57 AM   #9
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QuoteOriginally posted by boodiespost Quote
i see... thanks for the indept and clear explanation.

by the way, Marc. I can't believe you live in Denver. I lived in Colorado for 17 years before I moved here to California. Where abouts do you live? I lived everywhere in those 17 years, aurora, denver, littleton, highlands ranch, boulder, thornton... Good to see a fellow coloradan ^^
I'm in Wheat Ridge - just outside NW Denver. FWIW, I was in California (Berkeley) before that, but only for a year.
12-12-2009, 01:23 PM   #10
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Consider what small things you want to shoot in deciding what focal length of macro you'd want.
Stationary subjects can effectively be captured by a 50mm macro, whereas shooting bugs that don't like their personal space invaded may need 100+mm to give you enough working space not to disturb the bugs at their business and capture them well.
12-12-2009, 01:51 PM   #11
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The longer macro/closeup lenses are very well suited for close-ups of things such as bees and wasps. My Sigma 70-300 has a macro range between 200-300 mm which can be a pain in the neck (literally) while hiking because it's a little heavy and needs a monopod or tripod more often than a shorter lens. However in a canoe or kayak it's great as I can get shots of smaller flowers and insects from paddle length and I'm much more comfortable taking pictures of bees from 2 or 3 feet instead of a few inches.
12-12-2009, 02:55 PM   #12
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Not to add to the confusion here, but on my Kit lens version 1, you can focus pretty darn close with it.

This was shot with my K10D and Kit lens @ 55mm, the flower is about the size of a half dollar.

12-12-2009, 04:44 PM   #13
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i see, a 100 mm true macro lens seems to be the best choice so far as it's not too heavy and gives good focal length. Thank you for all for the inputs. That's a cool pic up there almost looks like the flower is pasted on there through photoshop, pretty cool
12-12-2009, 07:15 PM   #14
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I was fairly certain I had a photo of that same kind of flower taken with the D-FA 100mm Macro. It's been pretty heavily processed, but I don't have access to the original right now, but here's the processed version (though it is uncropped, so you can get a good idea of just how close you can get with a true macro).

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