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Old Sep 18, 2009, 1:28 AM   #1
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Default Macro confusion

I have previously understood (obviously wrongly) that macro lenses are for close up photography such as perhaps insect pictures and the lens are therefore able to be within a couple of inches.

I use a Tamron 18-250mm zoom with my A200 which is excellent for general picture taking but I am getting more and more disappointed when trying to photograph nearer objects such as flowers particularly the wild orchids which are in season here in WA....how can this be a macro lens?

I have tried the macro setting and other combinations and the macro setting doesn't seem to make any difference and I have yet to get a keeper.

My procedure is to hold the camera about 3 feet away and zoom in until the subject fills the viewfinder.

In a previous thread, TCav recommended the Tamron 90mm f2.8 lens to MVA Steve. Would this make such a difference?

Last edited by Bootneck3; Sep 18, 2009 at 2:03 AM. Reason: inclusions
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Old Sep 18, 2009, 1:50 AM   #2
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Every lens has a minimum distance that it can focus to. If you move the camera/lens any closer it cannot focus. Your Tamron lens can focus as close as 18".

With your lens I would switch it to manual focus, zoom out towards 250mm, turn focus ring to the closest possible focus, then move the whole camera/lens in and out from subject until you get focus.

Macro lenses can focus at closer distances then non macros and the Tamron 90 is a good one.

With macro you should use a tripod to get the sharpest shots possible
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Old Sep 18, 2009, 8:33 AM   #3
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Hi Bootneck3, I can highly recommend the tamron 90. The images are very sharp with great colour. But at full magnification you need to super steady or use a tripod, (as Iomitamike stated). I have found macro photography a challenge but the rewards can be fantastic.
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Old Sep 18, 2009, 9:31 AM   #4
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The Tamron 18-250 can create images with a magification of 1:3.5. That is, an object that is 35mm across, will be represented as 10mm on the image sensor. That's at the outer limits of what they could get away with calling it a "Macro" lens. In addition, at that's at a focal length of 250mm where that lens is soft and has a lot of CA anyway. I'm not surprised you haven't gotten any keepers.

Real 'Macro' lenses have a magnification ratio of at least 1:1 (perhaps 1:2) where the image projected onto the sensor is the same size as the subject (perhaps half-size.) Real 'Macro' lenses are also very sharp from edge to edge, something that can't be said about the Tamron 18-250.

There are no bad 'Macro' lenses (though Sony's are excelllent), but there are plenty of bad "macro" lenses (lenses that proport to do many things, macrophotography being just one.)

Another thing to consider is that, when selecting a 'Macro' lens, focal length can be your friend. A longer focal length can allow you to back up some, so as to not frighten the subject, and so as to not block your own light. The Tamron 90mm f/2.8 Di is a very good, very popular 'Macro' lens, but there are others to choose from, and your purposes might be better served by the Tamron 180mm f/3.5 Di LD or the Sigma 180mm f/3.5 EX DG, either of which don't cost much more than Sony's 100mm f/2.8.
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Old Sep 18, 2009, 9:15 PM   #5
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Thanks for quick replies which are very helpful.

I hoped to get one from you Steve as I know you were getting the 90mm Tamron.

I appreciate your advice Lomitamike on the manual focussing - I must admit that I have ignored that switch! Trouble with tripods when taking pictures of some of the wild flowers particularly the wild orchids is that the little blighters are often 3 or 4 inches tall amid undergrowth.

And Tcav as always gets to the heart of the problem.

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Old Sep 18, 2009, 10:21 PM   #6
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The true macro lenses that tcav mentions are all excellent, and will outperform zoom lenses (most prime lenses will), but lack the flexibility of zooms as "walk around" lenses. The Tamron 70-300 is an inexpensive but surprisingly good performer down to 1:2, but the 18-250 has proven quite capable, perhaps with better IQ than the less expensive lens, but with less magnification close up..

Actually, this lens will focus as closely as 8" from the lens front at maximum extension. Realize that the depth of field is very shallow, and at maximum extension the effective equivalent focal length is 375mm, and therefore subject to motion blur when hand held, so it can be done, but may then require sharpening in post processing as a result. A much better photographer than myself has posted many excellent close ups of insects and other subjects with this lens in the Pentax forum. FYI here are some of mine, all hand held - the first in Sony mount on an a350, and the next two in Pentax mount - take a look before giving up on the lens.



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Last edited by penolta; Sep 18, 2009 at 10:23 PM.
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