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08-10-2011, 04:16 PM - 1 Like   #16
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QuoteOriginally posted by reivax Quote
I remember reading about some equation that people use in order to use close up lenses that can try to get it to 1:1. If I'm using a 50mm or 55mm how could I achieve that?
My bible on this matter, FIELD PHOTOGRAPHY by Alfred Blaker (still a steal at Amazon) doesn't present CUL's this way. Oh bother. So I gargle for close-up lens magnification formula OR equation and I find:
M = F*D/1000
where M is magnification, F is host lens focal length, and D is dioptre of the add-on lens. Rewriting that to find D, we get
D = 1000*M/F
With a 50mm lens and 1x magnification, D=20. So you need to buy a couple +10dpt lenses; mine (with 49mm threads) cost about US$10 each on eBay (I have three). With a 100mm lens, you need just one +10dpt. Hay, you might even like the results! NOTE: Blaker says that magnification increases if you go from infinity to close focus with the host lens. But he doesn't give a formula.

(I *am* going to write an article about stuff you can hang on the front of a lens. Stay tuned!)


Last edited by RioRico; 08-10-2011 at 04:26 PM.
08-10-2011, 05:09 PM - 1 Like   #17
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I've been making forays into macro photography, on an extremely constricted budget, and I firmly believe that extension tubes are better than close up lenses. I've tried both, and the tubes give a sharper image, and more bang for your buck. The last thing you want to do is try to capture fine detail through the lens, plus two or three layers of (probably cheap quality) extraneous glass, when you can simply move the lens a bit farther from the sensor plane.

Here are a few of my shots with a cheap Pentax A 50mm f./2 and 68mm (one set of three tubes) extension. Max magnification with this setup is ~1.45:1, which means the FOV is around 16mm. Focused at infinity the FOV is a bit larger, but still less than 3cm.



Hoverfly. Wingspan approx 1cm.


Crab Spider.


Dew drops on a blade of grass.


Unknown spider, leg span ~1cm.

You can get a set of type A tubes for less than $50. Type A is important, because it lets you focus with a wide open aperture, stopping it down when you take a shot. If you really don't care about that, you can get a set of regular tubes for $10 on ebay.
08-10-2011, 05:26 PM   #18
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A set of type A tubes? Can you post a link? Having trouble finding it, or I'm looking for the wrong thing. Thanks.
08-10-2011, 05:51 PM   #19
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This kind is the same brand and model as the set I have. They're a bit hard to find, try searching for "Vivitar AT-22 tubes", or "auto extension tubes".

Other brands are available too. The important part is they have the aperture lever. You don't need the AF tubes, and they cost far more (up to about $180 for a set), because AF isn't important (or desirable) for macro work. There often isn't enough light for AF to even work for macro, so it's just a waste of money imo.

Edit: I guess the exception to that would be if you already have a nice macro lens, like one of the 100mm f./2.8 ones, and just want to push it farther. But if you can already afford one of them, the price of AF tubes probably won't phase you too much.

08-10-2011, 06:35 PM   #20
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QuoteOriginally posted by reivax Quote
A set of type A tubes? Can you post a link? Having trouble finding it, or I'm looking for the wrong thing. Thanks.
I had trouble finding affordable A-type tubes. So, following strong hints from others here, I made my own! A-type TC's are fairly common and cheap. My two averaged US$15 each. The trick: remove the glass. Then they become A-type macro tubes! The constraint: they are each about 25mm deep, so I can only use them as 25mm or 50mm extension. But as long as they have the A-type lens contacts, they provide auto-aperture control (including stopping down) and support PTTL flash.
08-10-2011, 09:38 PM   #21
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QuoteOriginally posted by RioRico Quote
I had trouble finding affordable A-type tubes. So, following strong hints from others here, I made my own! A-type TC's are fairly common and cheap. My two averaged US$15 each. The trick: remove the glass. Then they become A-type macro tubes! The constraint: they are each about 25mm deep, so I can only use them as 25mm or 50mm extension. But as long as they have the A-type lens contacts, they provide auto-aperture control (including stopping down) and support PTTL flash.
So then you guys would agree that tubes are without a doubt better and worth the investment over some close up lenses?

What about over the Raynox 250?
08-10-2011, 11:36 PM   #22
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The Raynox 150 and 250 have a reputation for being very good. I haven't had the pleasure of trying them yet, but I will eventually. It's another way to go, and better than the cheap chinese diopters we've been discussing.

Really, there are so many ways to go at macro, you can reverse your lenses, you can reverse one on the end of another, you can even use old enlarger (from darkroom equipment) lenses on a bellows (oh and bellows are really good! think variable length extension tube).

Both the Raynox lenses and extension tubes have a common strength. They can both be used on a variety of lenses, so you have more freedom to experiment. Conventional diopters only fit one thread size, so you would need multiple sets to use them on all your lenses. I took all these factors into account when I decided to focus on using tubes this year. Maybe in the winter I'll try the Raynox ones.

I wish the macro social group on the site here were more lively. Maybe we can help to do something about that?
08-11-2011, 07:40 AM   #23
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QuoteOriginally posted by reivax Quote
So then you guys would agree that tubes are without a doubt better and worth the investment over some close up lenses?

What about over the Raynox 250?
I wrote about these here: https://www.pentaxforums.com/forums/pentax-lens-articles/152336-cheap-macro-b...lose-work.html
It's not an either-or situation. All the techniques-tools-toys have their uses, their pros and cons.

* Extension (tubes and/or bellows) give the cleanest closeups, as they don't add glass between subject and frame (film or digital). But extension eats light.

* Lens reversal is just as clean, but forces you to work very close; and magnification results from extension, not reversal, so you may need tubes too.

* Corrected optical adapters like the Raynoxi are only minimally distorting, with brilliant results. Reverse-stacking is like using a Raynox, but with great control over magnification.

* Uncorrected adapters like the cheap closeup lenses are optically flawed but they're fun, cheap, and OK if you don't care about the image edges. Like Raynoxi, they don't diminish light.

* Fixed or macro-focusing TCs, or macro-focusing adapters, can be useful, but they can diminish image quality a bit. As with close-up adapters, you get to decide if that matters.

I'm working on a couple articles, on stuff to put in front of your lens (adapters, filters, etc) and stuff to put behind the lens (TC's, extension, etc). Stay tuned!

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