Extension tubes with a macro lens, a thought.

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GreenLarry
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Extension tubes with a macro lens, a thought.

Post by GreenLarry »

This got me thinking!

We know that if you attach extension tubes you get magnification depending on how much extension you put on, and to get lifesize with a 50mm lens you need 50mm of extension(extension/focal length=M:1)
But what if your 50mm is a macro lens and already gives you lifesize or 1:1, and you put 50mm of extension between it and the camera?

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twebster
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Post by twebster »

Hi ya' GreenLarry :D
But what if your 50mm is a macro lens and already gives you lifesize or 1:1, and you put 50mm of extension between it and the camera?
If you add another 50mm of extension tubes to a 50mm macro lens focused at 1:1 already, you then get 2:1 (2x life size).

Best regards, :D
Tom Webster
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Think about this...maybe Murphy is an optimist!!!

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GreenLarry
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Post by GreenLarry »

Oh now thats cool, free magnfication!Sometimes you DO get something for nothing!
All i need now is some extension tubes in Canon AF mount(pricey!)

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twebster
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Post by twebster »

Hi ya' GreenLarry :D
Oh now thats cool, free magnfication!Sometimes you DO get something for nothing!
Well...not really. You will lose another f. stop of light for focusing and exposure. Check out Kenko tubes. They are as good as the Canon tubes but much cheaper. :D

Best regards, :D
Tom Webster
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GreenLarry
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Post by GreenLarry »

You will lose another f. stop of light for focusing and exposure
Oh yea and a few years ago that would be a problem, but with TTL flash available to all, its just great!

I do have trouble selecting a smaller aperture than what the camera suggests tho, will have to experiment with it on Manual.

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Post by Bald Eagle »

GreenLarry wrote:
You will lose another f. stop of light for focusing and exposure
Oh yea and a few years ago that would be a problem, but with TTL flash available to all, its just great!

I do have trouble selecting a smaller aperture than what the camera suggests tho, will have to experiment with it on Manual.
I have taken literary thousands of shots with my Kenko Extension Tubes, they are worth their weight in Gold. Try these settings, its one of my favorites, manual setting, manual focus, ISO of 100 to 400, depending on lighting, ( I try to use flash on these settings for fill-in) 1/125, f11 to f22. I use a tripod for this with a remote shutter release. all this with 68mm of tubes on a Tamron 28-300 Macro. hope this helps.
Always look at Nature with wide eyes.
Rick Cowen
Canon 5D, Canon 70-300 IS USM.Sigma 150 2.8 Macro, Sigma 170-500. A set of Kenko tubes. Check out my Gallery here!

http://www.pbase.com/1bald_eagle/macro

Sergio Zalewska
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Post by Sergio Zalewska »

Check my set-up with Kenko tubes and a Tominon 17mm lens.

http://www.macrophotography.org/modules ... _album.php

The problem is to find these lenses, I was lucky enough to get one, that I glued to a eos-M42 adapter, because the lens has a M40 screw :shock:

Now I will use it in a bellows.. magnification will be close to 40X.
You have to set your camera to manual or TV and change the shutter speed until it shows right exposure (stop-down metering)

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Post by rjlittlefield »

Sergio Zalewska wrote:Tominon 17mm lens....in a bellows.. magnification will be close to 40X.
Sergio, I'm confused. Seems like 40X onto the sensor using a 17mm lens would require roughly 680mm of extension -- kind of an unwieldy bellows. How are you measuring magnification?

--Rik

Sergio Zalewska
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Post by Sergio Zalewska »

You are right Rik.
40X is the specification of this lens for the original setup with Polaroid MP-3/4 system which has a big Bellows, and I was measuring magnification as if I had taken the picture with a film camera (36mm), but it was a digital with a 22,2mm sensor.
So, let's see: If with no tubes it gives me 5,5 mm in a 22,2 sensor, it means 4X magnification, and the distance from "center" of lens (sorry if I do not know the actual name of it) is 17x4=68mm (roughlly).
If I ad 36+20+12mm tubes I will have a total of another 68mm (coincidence!)
So, with tubes plus the normal distance of lens, the total distance will be 136mm. 136/17=8X magnification (I pictured 2,5 mm which is 22,2/2,5= 8,8X) ok, for me the calculation is close enough :wink:
With a bellows of 200mm I will have (200+68 )/17 = 15,7X magnification, but I can add the tubes before the bellows...
(200+68+68 )/17 = 19,7X :shock:
I can add some more screwed extension tubes to the other side... can you imagine the assembled device??? :D
(200+68+68+68 )/17 = 23,7X what means I would be picturing a 0,93mm subject...
OK OK better to use the scope that I just put up hehe...

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