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01-03-2012, 06:40 PM   #1
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Extension tubes for a newbie

Ok, so I got these tubes from Ebay eBay Australia: Buy new & used fashion, electronics & home d?r and they finally arrived yesterday. They have aperture control but no electrical pins for autofocus etc... I can take photos with the aperture fully open but the DOF is terrible. Is there any way to close the lens a bit? None of my lenses have manual aperture control. How do I use them with my k-X? which modes/green button settings should I use?

01-03-2012, 07:19 PM   #2
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These are fully manual tubes, no electrical contacts.

Just to clarify they do not have aperture control on digital unless the lens has an aperture ring. And the electrical pins have nothing to do with auto-focus, except the SDM contacts which is whole different thing.

The short answer is these must be used in manual "M" mode and with a lens that has an aperture ring. Or wide open as you already discovered.
01-03-2012, 07:36 PM   #3
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jatrax is quite right. You need a lens with an aperture ring and a PK bayonet mount (no M42s). Every K- or M- or A- or F- or FA-series (but not FA-J) lens has an aperture ring. Many decent PK mount lenses from Vivitar or Sears or Toyo or others will work. Or you might start with a M50/1.7 or, if your budget is extremely low, an M50/2.

With any of these lenses, be sure that USING APERTURE RING is set to PERMITTED in your Custom Menu. Set exposure mode to M(anual) and use the Green button for stop-down metering and exposure. Unfortunately, lacking A-type aperture-control pins, pTTL flash isn't supported, so flash use demands a bit of trial-and-error. At least you won't be burning film while you learn!
01-03-2012, 07:38 PM   #4
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Thanks guys. Clarifies things alot. So will a 50mm prime be best for use with extension tubes?

01-03-2012, 07:48 PM   #5
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QuoteOriginally posted by Livert Quote
Thanks guys. Clarifies things alot. So will a 50mm prime be best for use with extension tubes?
That should make a great macro setup. I use that when I don't want to carry my dedicated macro lens.

I also use extension tubes with my 100mm macro and get magnification better than 2:1. Combined with focus stacking software, that makes for amazing closeups.
01-03-2012, 08:14 PM   #6
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@mysticcowboy,
Do you mean 2:1 or 1:2? Reaching 2:1 with a 100mm lens takes 300mm of extension, and a tube set is only 50mm long.

@Livert,
I think 50mm with your tubes makes a good, inexpensive way to start shooting macro. You could get greater magnification with a 28mm lens, but you'd have to work much closer to your targets. You could get more working room with a 135mm lens, but you'd need more tubes for decent magnification. 100mm lenses ain't cheap. So a 50mm lens is a good beginning.
01-04-2012, 04:14 PM   #7
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QuoteOriginally posted by RioRico Quote
@mysticcowboy,
Do you mean 2:1 or 1:2? Reaching 2:1 with a 100mm lens takes 300mm of extension, and a tube set is only 50mm long.
Are you sure? The lens does 1:1 When I take the same subject, at closest focus, with and without the tubes, the image appears about twice the size at 100%.
01-04-2012, 05:52 PM - 1 Like   #8
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QuoteOriginally posted by mysticcowboy Quote
Are you sure? The lens does 1:1 When I take the same subject, at closest focus, with and without the tubes, the image appears about twice the size at 100%.
I can confirm that you are right. When I attach the complete set of Vivitar AT-23 extension tube set to the Tamron 72B 90/2.8 1:1 Macro lens, I get about 2.1:1 magnification. The phenomenon RioRico is describing probably is for a non macro 100mm lens, and do not seem to apply to macro lenses with extension tubes. Here are a couple of shots I took few minutes ago, first is Tamron CT-105,105/2.5 non macro and the second is Tamron 52B, 90/2.5 1:2 macro (I don't have the 72B with me at the moment, I lent it to my niece). Both shots had the complete set of AT-23 extension tubes attached. Images are not in great focus but they're legible.

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01-05-2012, 01:57 PM   #9
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When a lens is extended (moved away from the sensor) image size increases;

Mag.change = extension.change/focal.length -this is always true...but you don't always know the focal length.

The focal length of an Internal Focus (IF) lens depends on its focus setting, typically a 100mm IF macro lens is about 60mm actual focal length when its focusing ring is turned all the way.

Therefore, when an IF lens is focused closer than infinity, extension with a tube will cause more magnification than expected.

=================math alert=================================

non-IF lens + tube
mag.total = mag.lens + extension/focal.length mag.lens means mag before extension tubes added.

100%-IF lens + tube
mag.total = mag.lens + ( 1 + mag.lens) extension/focal.length.nominal

Last edited by newarts; 01-05-2012 at 02:47 PM.
01-05-2012, 11:49 PM   #10
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QuoteOriginally posted by excanonfd Quote
I can confirm that you are right. When I attach the complete set of Vivitar AT-23 extension tube set to the Tamron 72B 90/2.8 1:1 Macro lens, I get about 2.1:1 magnification. The phenomenon RioRico is describing probably is for a non macro 100mm lens, and do not seem to apply to macro lenses with extension tubes. Here are a couple of shots I took few minutes ago, first is Tamron CT-105,105/2.5 non macro and the second is Tamron 52B, 90/2.5 1:2 macro (I don't have the 72B with me at the moment, I lent it to my niece). Both shots had the complete set of AT-23 extension tubes attached. Images are not in great focus but they're legible.
Thanks for the pics. Now I don't have to post any +1
01-06-2012, 05:34 AM   #11
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I can also confirm what mysticcowboy and excanonfd have said. When I add extension tubes to my Tamron 90mm macro I get considerably greater magnification than 1:1. I've never fully measured it but it appears to be close to 1:2.
@ Livert a good way to get an extension tube with electrical contacts for aperture control is to buy a cheap 1.5X telephoto converter with contacts and just remove the glass. It works quite well and is less frustrating than trying to find extension tubes with contacts. I found one on eekbay for $30 and it works quite well. I've personally found AF to be useless in macro work, but electronic aperture control is quite helpful.

NaCl(there are extension tubes out there with contacts but they are very hard to find)H2O
01-06-2012, 01:04 PM   #12
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QuoteOriginally posted by NaClH2O Quote
I can also confirm what mysticcowboy and excanonfd have said. When I add extension tubes to my Tamron 90mm macro I get considerably greater magnification than 1:1. I've never fully measured it but it appears to be close to 1:2.
1:2 = 0.5x. I think you mean 2:1 which is 2x. Add 90mm of extension to a fully-extended 90mm macro lens and you'll reach 2:1.
01-06-2012, 07:50 PM   #13
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QuoteOriginally posted by RioRico Quote
Add 90mm of extension to a fully-extended 90mm macro lens and you'll reach 2:1.
That's my understanding too, but I can't test it. I'm a bit confused why you said above:

QuoteOriginally posted by RioRico Quote
Reaching 2:1 with a 100mm lens takes 300mm of extension
Shouldn't that be 200mm extension for a regular 100mm lens, and 100mm extension for a 1:1 capable 100mm macro lens (fully focused in)? I guess I'm not getting where the extra 100mm comes from, since extension equal to focal length should get to 1:1, and doubling that extension should get to 2:1, no?
01-06-2012, 08:13 PM   #14
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The formula is: MAG = (TE-FL)/FL where TE is total extension and FL is focal length. A camera lens at infinity focus has TE=FL so MAG=0. ("Camera lens" excludes enlarger-projector-copy-etc lenses.) A camera lens with another FL-worth of extension, or a fully-extended 1:1 macro lens, reaches 1:1. To reach 2:1 takes another FL-worth of extension. So reaching any specific MAG needs (MAG+1)*FL of extension.

Let's plug in the numbers. A 100mm camera lens at infinity focus by itself gives no magnification -- FL=TE. A 100mm camera lens with 100mm extension has total extension of 200mm and reaches 1:1. A 100mm camera lens with 200mm extension has total extension of 300mm and reaches 2:1. If I used a 100mm enlarger lens, it would need 300mm of tubes and/or bellows to reach 2:1. If I used a 100mm 1:1 macro lens fully extended, it would need another 100mm to reach the 300mm TE for 2:1 magnification.

Hope this helps!
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