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Old May 20, 2010, 5:39 AM   #21
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1) 1:2 magnification means that the image on the sensor is 1/2 the size of the object being photographed. So when compared to 1:1 macro, that translates to lower resolution (1/2 actually) and not necessarily image quality. Am I right? I understand that 1:1 is true macro photography but do I (someone who does not take pictures for profession but for sheer hobby) need it?
Yes. 1:2 magnification means that the image on the sensor is half the size of the subject. That is, the image of a subject that is 1 inch long will be 0.5 inch on the sensor. But a 1:1 magnification means that the image on the sensor is the same size as the subject. So the image of a subject that is 1 inch long will be 1 inch long on the sensor. The image of the subject is projected onto 4 times as many photoreceptors (twice the vertical resolution and twice the horizontal resolution.) So 1:1 means greater resolution.

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2) Thanks for explaining about the working space. ... However, the sigma 105 macro and the tamron 90 are a little beyond my budget. Sigma 50mm f/2.8 EX DG Macro Lens looks reasonable although $300 is still a little more than what I want to spend.
The Sony 30mm f/2.8 Macro lens is an excellent lens if you can get close enough without frightening your subject, and keep from blocking your own light. For shooting insects in nature, this is not a good choice. In fact it's not a good choice for shooting flowers in nature. But if you're doing product photography in a light box, it's an excellent choice.

But for what you want to do, you need a longer lens. The Tamron 90/2.8, Sony 100/2.8 and Sigma 105/2.8 are all excellent choices, and if they're out of your price range, consider the used market. I've done well shopping on eBay, KEH.com and the used equipment departments of B&H and Adorame. Some people here have even stumbled on bargains at local pawn shops, but I think that requires a good bit of luck.

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5) Thanks for making me aware of the problems with Sigma lenses. I like the Tamron 70-300 Di LD because of the 300mm zoom. However, the macro does not sound that great. It says the Macro magnification ratio is 1:7.4. If 1:2 bad, this sounds even worse. Also what is its maximum focussing distance?
The Tamron 70-300 Di LD is a 1:2 macro lens. In all other respects, it is a conventional telephoto zoom lens. It focuses to infinity.
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Old May 20, 2010, 5:43 AM   #22
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On a related note, have any of you experimented with reversing a lens using a reversing ring? What are the cons?
All of the reasons you don't want to use extension tubes also applies to reversing rings. Plus, AF and AE don't work, and you can only use M (Manual) Mode.
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Old May 20, 2010, 7:18 AM   #23
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Thanks TCav. Having the facts helps me take a more informed decision. From where I started, I have much better idea now and my choices have narrowed down to true macro lenses and telephoto zoom lenses.

And since all the true macro lenses with a good working distance are expensive, do you think it is safe to buy a telephoto lens for macro photography? The extra telephoto zoom is also a good addition to my kit. Besides the 1:2 magnification, what are the other drawbacks?

On the same note, the Tamron 70-300 Di LD for Sony is 1:7.4 (as per Amazon specs). Probably its incorrect:

http://www.amazon.com/Tamron-70-300m.../ref=de_a_smtd

Yet an another alternative is to get a 50mm macro lens. Shoturtle mentioned about the 1.5 crop factor of Sony. I believe he is talking about the Smart Teleconverter 2X Zoom feature of the Sony. So does that mean that I can have a working distance of 100mm for that 50mm lens?

Let me know your thoughts.

Thanks,
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Old May 20, 2010, 9:04 AM   #24
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The 1.5x crop factor is the multiplier that your camera has. It is an APS-c sensor. So any lens you mount, you will need to apply the 1.5 multiplier to get the 35mm film equivalent range. All lenses give you zoom range base on 35mm film. So you kit lens gives you a 35mm eq of 27-83mm.
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Old May 20, 2010, 3:42 PM   #25
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Thanks TCav. Having the facts helps me take a more informed decision. From where I started, I have much better idea now and my choices have narrowed down to true macro lenses and telephoto zoom lenses.

And since all the true macro lenses with a good working distance are expensive, do you think it is safe to buy a telephoto lens for macro photography? The extra telephoto zoom is also a good addition to my kit. Besides the 1:2 magnification, what are the other drawbacks?
1:2 magnification isn't bad. Your 55-200 only does 1:3.5, so 1:2 would be a big improvement. Have you tried to get close-up shots with it that you couldn't do?

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On the same note, the Tamron 70-300 Di LD for Sony is 1:7.4 (as per Amazon specs). Probably its incorrect:

http://www.amazon.com/Tamron-70-300m.../ref=de_a_smtd
Yes. That's incorrect. See http://www.tamron.com/lenses/prod/70300_di_a017.asp

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Yet an another alternative is to get a 50mm macro lens. Shoturtle mentioned about the 1.5 crop factor of Sony. I believe he is talking about the Smart Teleconverter 2X Zoom feature of the Sony. So does that mean that I can have a working distance of 100mm for that 50mm lens?
Even the 50mm has a relatively wide angle of view, and presents the same difficulties as the 30mm, though slightly less bad. What shoturtle is talking about is the "crop factor" that your A300's APS-C size image seonsor has. It affects all lenses, and so doesn't negate the fact that, if the 30mm lens is too wide, the 50mm won't be a lot better.

For the purposes of this discussion, the "crop factor" is immaterial.
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Old May 20, 2010, 3:52 PM   #26
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The 50mm will give you better working distance, with 1:1 without the need for tubes or lenses. But as Tcav pointed out, it is still a tight working distance vs a 90, 100, or 105mm macro lens. But you get more then the 30mm and get true 1:1. Flower and none leaving subject will work fine with a 50mm. But with something that can fly or crawl away. You want a 90mm or higher.

If you really want to get into Macro. You will want a 1:1 lens mounted on a tripod for those shots.

But 1:2 is good for close up shots. But if you are looking to get the pollen off a flower, you are better off with a 1:1 macro lens.

But the crop factor does let you get closer into the subject and plays a bit into the shot.
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Old May 20, 2010, 4:05 PM   #27
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The minimum focusing distance and the magnification ratio are not affected by the size of the image sensor.
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Old May 20, 2010, 4:08 PM   #28
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But the crop in focus more pixel on the area of that you want to focus on. So it effects the what is seen at the end. So is you are a 1:1.5 of the whole flower, you do not need to be as close to frame. And 50mm way easier to work with then a 30mm at 1:1, and a breeze to work with at 1:2 when shooting hand held.
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Old May 20, 2010, 8:34 PM   #29
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But the crop in focus more pixel on the area of that you want to focus on. So it effects the what is seen at the end. So is you are a 1:1.5 of the whole flower, you do not need to be as close to frame.
That's pixel density and has nothing to do with the size of the image sensor either.
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Old May 20, 2010, 11:41 PM   #30
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1) How is the focal length of a lens (say, 70-300 mm) related to the focus distance? Is it a pure geometric relationship or does it have some dependance on the lens-make?

2) The Tamron 70-300mm has a minimum focus distance of 37.4 inches for macro. This sounds like a good working distance especially when photographing insects. I checked the minimum focus distance of a Sigma 105mm F2.8 EX macro lens and its 12.3 inches. The telephoto lens has a larger minimum focus distance than the macro lens, so does that mean that the telephoto lens is better in this respect? Or is there some optimum minimum focus distance for macro photography?

3) Except for the fact that a macro lens takes pictures with 1:1 magnification, are there any disadvantages with using a telephoto lens for macro photography? I believe the macro lenses are faster and sharper. Is that true?

4) I had close up photography in mind and not necessarily true macro. Not being able to get to the pollen is fine with me although if I can't get a clear shot of the pistils and stamens of a flower, I won't be happy. I've attached a sample image to show how close I can get with my 55-200mm.

5) On a side note, if I get the Tamron 70-300mm, can I eliminate the Sony 55-200mm lens? Or do you think the quality of the Sony lens is superior to the Tamron's and hence I should keep it with me.

Last edited by nevjac; May 20, 2010 at 11:49 PM.
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