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05-08-2009, 03:30 PM   #1
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Extension tubes question

I'm craving more magnification from my sigma 105mm macro lens. It seems 1:1 is just not enough anymore

My first question would be, will extension tubes plus my macro lens set to 1:1 give me greater than 1:1?

My second question is if this set of extension tubes would be fine to practice/get used to higher magnification if the above is true? Macro Extension Tube Ring for Pentax K Mount Series - eBay (item 250419595730 end time Jun-04-09 20:55:43 PDT)

I realize I would have to use the aperture ring but I'm totally fine with that since this is just for practice. Other than that will it work?

05-08-2009, 03:45 PM   #2
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i've used them before on full manual but the DOF gets very thin.
05-08-2009, 03:51 PM   #3
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I understand I'll have to use a high F-stop/focus stack.....I just want more magnification.
05-08-2009, 03:55 PM   #4
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QuoteOriginally posted by yeatzee Quote
I understand I'll have to use a high F-stop/focus stack.....I just want more magnification.
These ext.tubes do not keep the aperture open, as they are not 'auto' extension tubes. So, with high F stops the viewfinder will be totally dark, so you have to focus with the aperture ring fully open, and then you have to stop it down to your desired F-stop and shoot...but, remeber, the dof is so thin, so once you fiddle around with the aperture ring, is the object still in focus...if the lens is mounted on a tripod and the object is static, you'll be fine....so for testing, why not....I could not handhold and do it...so I removed some TC's with A contacts and did it that way....Hope this helps.

05-08-2009, 04:43 PM   #5
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Right, I understand this.....so if I understand correctly I will get more magnification than 1:1?
05-08-2009, 04:50 PM   #6
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QuoteOriginally posted by yeatzee Quote
Right, I understand this.....so if I understand correctly I will get more magnification than 1:1?
Yes.

Magnification_increase = Tube_length/Focal_length

One set of tubes will add 55/105 ~ 1/2 to your magnification so you might want two sets of tubes that'd take you to ~2:1.

Iowa Dave

You might consider bellows, they are a little easier to use than tubes I think.
http://shop.ebay.com/items/?_nkw=bellows+pentax+K&_sacat=0&_trksid=p3286.m27...ntax&_osacat=0

Last edited by newarts; 05-08-2009 at 04:58 PM.
05-08-2009, 05:03 PM   #7
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QuoteOriginally posted by yeatzee Quote
Right, I understand this.....so if I understand correctly I will get more magnification than 1:1?
Disclaimer: This is my thinking, not actual experience, so it may not be correct.

You will definitely get greater magnification than 1:1.

To get to 2:1, you need to add 100mm of extension tube. By then, the exposure factor is X 7. Autofocus is of course not possible. Manual focus is difficult.

A flash gun and in particular, a solid tripod with a macro rail will help trememdously.
05-08-2009, 05:16 PM   #8
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QuoteOriginally posted by yeatzee Quote
Right, I understand this.....so if I understand correctly I will get more magnification than 1:1?
Yes....................

05-08-2009, 05:20 PM   #9
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with the linked set (9mm, 16mm, and 30mm tubes) above, what magnification am I looking at?
05-08-2009, 05:33 PM   #10
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QuoteOriginally posted by yeatzee Quote
with the linked set (9mm, 16mm, and 30mm tubes) above, what magnification am I looking at?
Like I said, (9+16+30)/105 = 55/105= 0.52x increase over the 1:1 you already have.

Iowa Dave
05-08-2009, 05:48 PM   #11
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hrmm.....any way to get more than that?

Thanks for all the help
05-08-2009, 05:56 PM   #12
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QuoteOriginally posted by yeatzee Quote
hrmm.....any way to get more than that?
Something in front of the lens, e.g. a Raynox 250.

IQ will suffer (but the Raynox is not too bad).

A nice thing of this over extension tubes is that you don't lose light.
05-08-2009, 06:03 PM   #13
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Hows about a TC?
Would it be better than using extentions?

Ray
05-08-2009, 06:08 PM   #14
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You could try a bellows.
05-08-2009, 06:13 PM   #15
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wow I just re-read the thread and didn't realize people answered my questions already lol......stupid page not loading fully

I have been looking at some bellows....all of them on ebay say K-PK mount...what does that mean? Would this work with my sigma 105mm? I know nothing about bellows, so what magnification could I get with them coupled with the sigma? I would still have to do the technique stated by pcarfan with bellows though, correct?
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