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01-03-2011, 08:12 PM   #1
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Macro Extension Tubes and Aperture

Hi all,

I was considering getting some cheap macro tubes off eBay but noticed they're all fully manual. I'm shooting with a K7 and Sigma 70mm/2.8 macro lens that doesn't have an aperture ring. I'm wondering if there's any trick to being able to set the aperture?

Is there any way to make the K7 set and hold the aperture so that when you take the lens off the body the aperture is set to what you want? My understanding is that lens is always wide open until you take the photo and I'm guessing trying to take the lens off during an exposure would be a very bad idea...

So is there any way to set the aperture or would I need to buy an extension tube with aperture contacts?

Cheers,
Steve

01-03-2011, 08:20 PM   #2
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If the lens does not have an aperture ring, you need extension tubes (or any other rear-mounted accessory) with electrical contacts.

You can try to locate a cheapo teleconverter with electrical contacts and remove the optics, like the one on the right below:

01-03-2011, 08:33 PM   #3
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Ah ok, thanks. I assume a teleconverter with contacts and an extension tube with contacts would be a similar price? But I guess teleconverters are easier to find?

How difficult is it to remove the optics?
01-03-2011, 09:11 PM   #4
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QuoteOriginally posted by Stiv Quote
I assume a teleconverter with contacts and an extension tube with contacts would be a similar price? But I guess teleconverters are easier to find?
I don't know about "similar price." At least in the old days, TCs outnumbered ETs probably 5 to 1 so TCs are easier to find in the used market. Most people bought TCs due to the marketing hype and never used them.

I currently have 3 ETs (ex-TCs) with electrical contacts and 6 TCs without. All of them were part of package deals.

QuoteOriginally posted by Stiv Quote
How difficult is it to remove the optics?
Not too difficult, I use a dial caliper as a spanner to remove the optics. If that fails, a hammer and an old screw driver will always work

01-03-2011, 09:56 PM   #5
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A quick look for international sellers on eBay came up short, best I can do is brand new for around AU$100 which is a bit much for something I'm only curious about.

I wonder if I could somehow incorporate my kit 18-55mm lens and do some kind of reverse mount setup I've been hearing about but haven't done any research on...
01-03-2011, 10:32 PM   #6
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QuoteOriginally posted by Stiv Quote
A quick look for international sellers on eBay came up short, best I can do is brand new for around AU$100 which is a bit much for something I'm only curious about.

I wonder if I could somehow incorporate my kit 18-55mm lens and do some kind of reverse mount setup I've been hearing about but haven't done any research on...
they have reverse rings... but like the extension tube, if you do not have any contacts you're better off buying manual lens for these task (grab a 50mm f/1.4 for like 40 bucks or less, or maybe a 28 f/2.8 for like 10-15 dollars), it can be any brand since you're using the thread of the lens instead of the mount...

and off you go lol. focusing is now by moving the camera instead of the focus ring (that's what I heard from people).

I got lazy and bought macro lens instead... I think that's the easiest solution, and since my macro lens got AF i can just use it as a regular lens to shoot stuff too haha.
01-04-2011, 02:06 AM   #7
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Cheap manual macro tubes are great when mounting manual lenses, and bloody impossible for automatic lenses. Automatic macro tubes, whether aperture or focus, are rare and costly, so butchering at TC is about the only way to retain functionality -- and AF TC's are rare and costly too. Of course, AF is irrelevant for real macro shots. But a ringless lens MUST be on the right extension.

To get closer with a ringless lens, you need either 1) auto-aperture extension, 2) a Raynox or similar strap-on, or 3) a reversed lens stack. A longer lens needs more extension to gain much magnification, which means butchering more than one not-cheap TC. A strap-on or reverse stack would be much more manageable, but consider that a reverse stack means a working distance of 45.5mm, under two inches. That close, live bugs are scared off. So I'd vote for a Raynox.
01-04-2011, 02:49 AM   #8
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So a Raynox just sits on the end of the lens right? Kind of like a super filter? Does everyone refer to these as Raynox because they are the only brand that make these or just because they're the best?

Would reverse mounting my kit 18-55mm lens onto the end of a correctly mounted 70mm 1:1 macro lens do anything? I just tried to give it a go hand-held and I only got smallish circle image in the middle of the sensor, the rest is black.

I really should research this stuff rather than stumbling around in the dark!

01-04-2011, 03:31 AM   #9
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Raynox is the best right now. I'm sure there are others that are ok, but sifting through all the garbage that's out there to find them makes choosing the Rayonox that much easier.
01-04-2011, 06:11 AM   #10
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If you reverse mount a lens without an aperture ring, the aperture control lever is exposed. It can be held in place to adjust the f-stop as needed. I found a piece of flexible plastic tubing works well.

The above photo summary shows a kit lens directly reversed to a camera, but the reversing trick will also work on tubes, bellows, etc. The macro example photo strips are of a laptop screen, repetition pattern about 1/4mm. "Clearance" ~ Working Distance.

Dave
01-04-2011, 06:21 AM   #11
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QuoteOriginally posted by Stiv Quote
So a Raynox just sits on the end of the lens right? Kind of like a super filter? Does everyone refer to these as Raynox because they are the only brand that make these or just because they're the best?
Maybe not the best, but very, very good and certainly the most cost effective ~$50USD delivered!

Magnification=(primary lens focal length)/(close up lens focal length).

For long lenses use Raynox DCR 150 (focal length & working distance 208mm).
For wide lenses use Raynox DCR 250 (focal length & working distance 125mm).

Dave

QuoteQuote:
Would reverse mounting my kit 18-55mm lens onto the end of a correctly mounted 70mm 1:1 macro lens do anything? I just tried to give it a go hand-held and I only got smallish circle image in the middle of the sensor, the rest is black.
The magnifications resulting would be too big and the small aperture would cause vignetting as you discovered.

Guessing that your 70mm macro lens has a maximum mag of 0.5x, adding Raynox lenses would result in max mags as follows:
Raynox 150, 1.00X
Raynox 250, 1.34X

Last edited by newarts; 01-05-2011 at 02:41 PM. Reason: incorrect working distances removed
01-04-2011, 09:25 AM   #12
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QuoteOriginally posted by newarts Quote
If you reverse mount a lens without an aperture ring, the aperture control lever is exposed. It can be held in place to adjust the f-stop as needed. I found a piece of flexible plastic tubing works well.

The above photo summary shows a kit lens directly reversed to a camera, but the reversing trick will also work on tubes, bellows, etc. The macro example photo strips are of a laptop screen, repetition pattern about 1/4mm. "Clearance" ~ Working Distance.

Dave
lol awsome, i never thought of doing it like that... but yes that'll definitely work, just jam that sucka up and you're good to go.
01-04-2011, 05:12 PM   #13
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QuoteOriginally posted by newarts Quote
Maybe not the best, but very, very good and certainly the most cost effective ~$50USD delivered!

Magnification=(primary lens focal length)/(close up lens focal length).

For long lenses use Raynox DCR 150 (focal length & working distance 208mm).
For wide lenses use Raynox DCR 250 (focal length & working distance 125mm).

Dave



The magnifications resulting would be too big and the small aperture would cause vignetting as you discovered.

Guessing that your 70mm macro lens has a maximum mag of 0.5x, adding Raynox lenses would result in max mags as follows:
Raynox 150, 1.00X (208mm working distance)
Raynox 250, 1.34X (125mm working distance)
The lens I have is already 1x magnification:

Sigma-MACRO-70mm-F2.8-EX-DG-AF

So does that mean with the Raynox I could achieve 2x mag? And would it also mean I could get 1x mag from further away? With the 70mm my working distance is pretty short.

I was shooting a jumping spider the other day and whenever I got in real close he wanted to jump on the lens!
01-04-2011, 06:23 PM - 1 Like   #14
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QuoteOriginally posted by Stiv Quote
The lens I have is already 1x magnification:

Sigma-MACRO-70mm-F2.8-EX-DG-AF

So does that mean with the Raynox I could achieve 2x mag? And would it also mean I could get 1x mag from further away? With the 70mm my working distance is pretty short.

I was shooting a jumping spider the other day and whenever I got in real close he wanted to jump on the lens!
When you add a closeup lens of focal length f' to a lens of focal length f, the combination has a magnification of m'=f/f'

If the original lens is extended to a magnification of m" before the closeup lens is added, the total magnification m is:

m=(1+m')(1+m")-1

Your 70mm lens plus the Raynox 150 has a magnification of 70/208=.336, and with the Raynox 250, a magnification of .56. When combined with the initial 1X magnification of your macro lens this yields a total maximum magnification of:

Raynox 150, m= 1.67X working distance 208mm EDIT the working distance is wrong; see my later post
Raynox 250, m= 2.12X working distance 125mm EDIT the working distance is wrong; see my later post

Dave

PS "And would it also mean I could get 1x mag from further away?" - yes. With the bare 70mm lens the working distance at 1:1 is about 140mm; with the Raynox 150, at 1:1 the working distance would be 208mm - 50% greater. EDIT the working distance is wrong; it is actually around 104mm - see my later post

Last edited by newarts; 01-05-2011 at 07:44 AM.
01-05-2011, 03:20 AM   #15
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Brilliant, I think I get it now. Thanks for your help.

I wasn't sure where you were getting those Raynox focal lengths from but I've discovered focal length = 1000/diopters. (the Raynox website lists diopters not FL)

QuoteOriginally posted by newarts Quote
PS "And would it also mean I could get 1x mag from further away?" - yes. With the bare 70mm lens the working distance at 1:1 is about 140mm; with the Raynox 150, at 1:1 the working distance would be 208mm - 50% greater
The only thing I'm not sure of is how you worked out the 1:1 working distance. Isn't 208mm the working distance for x1.67 not x1.0?
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