Extension Tubes

Barnster · 11-02-2009, 06:07 PM

I just received a set of extension tubes today.This will be the first time that I ever used extension tubes.I have 12,20 & 36mm.Is their any tricks of the trade on how to use them properly to get good results.Also is a 50mm lens a good lens to use on the end of the tubes????????

*Ash* · 11-02-2009, 07:19 PM

You should get very good results with a 50mm lens on the end of one, two or all three of these extension tubes. You'll be able to achieve quite high magnification but will need accurate focusing to get it right.

Flick to M mode and go for it!
Show us what you get!

*Nick Siebers* · 11-02-2009, 08:01 PM

Have a lot of light around, and/or use a tripod! I never got macro results like I wanted until I sucked it up and busted out my tripod. Either not enough DOF, of shutter speed too slow and camera shake handheld. Exception - sometimes a (bounced) flash will do.

Banjo · 11-02-2009, 09:12 PM

Originally Posted by Barnster

I just received a set of extension tubes today.This will be the first time that I ever used extension tubes.I have 12,20 & 36mm.Is their any tricks of the trade on how to use them properly to get good results.Also is a 50mm lens a good lens to use on the end of the tubes????????

First, there are tubes and tubes: some tubes permit open diaphragm metering: these are best. You can then proceed (with regard to focusing, framing, and TTL metering as though no tube was there.

Then, there are tubes which don't connect the lens to the camera to let the metering know what aperture you're in. Whatever aperture you set on the lens, the diaphragm stays that way (but it doesn't link with the metering). This means not only metering in the stop-down mode (which can be OK for cameras with TTL metering) but also stop-down focusing and framing (which is a pain).

You will soon find that the longer the tube you use, the larger the magnification, but also the shallower the depth of field, and the smaller the effective aperture (i.e., less light on the film/sensor).

If interested in close-up photography of flowers (e.g., roses) you will find that your shortest tube (12mm) may be sufficient for the purpose.

What you do is add the tube, set the lens to infinity, then move (rock back and forth) the whole camera, tube, and lens assembly as a single unit until you get focus/framing, then shoot. This is a trick which may take a bit of practice to get right.

If you attempt to focus using the focus ring, you will gradually increase the magnification, reduce the working distance, and reduce your effective aperture still more, as you extend the lens (via the helical), effectively increasing the lens to sensor/film distance. (It's just as though you were adding more length to the tube). Then you would still need to "rock back and forth" to focus.

Your 12mm tube (with the lens at "infinity") will give you approximately 1 to 4 (or x0.25) magnification.
50mm of tube and a 50mm lens (set to infinity) will give you 1:1 (or x1.0) magnification (and plenty of hassles regarding DOF and focusing).

Have fun!

PS: you may find something of interest on this thread:

http://www.apug.org/forums/forum206/...converter.html

*pdxbmw* · 11-03-2009, 02:48 AM

I prefer to use a 28mm with extension tubes for really close up abstract stuff.

Lowell Goudge · 11-03-2009, 05:50 AM

just to give a real good idea on what you achieve with extension tubes on a 50mm

my SMC 50mm F1.4 has a minimum focus distance of 400mm and a magnification ratio of 1:0.14

if I add a 12mm extension tube i get
-maximum focus of 258 mm
- minimum focus of 181 mm
- magnification ration of 1: 0.38

if I add a 20mm extension tube i get
-maximum focus of 175 mm
- minimum focus of 142 mm
- magnification ration of 1: 0.49

if I add a 36mm extension tube i get
-maximum focus of 119 mm
- minimum focus of 108 mm
- magnification ration of 1: 0.64

WHat you can see is that as you increase the extension tube length, the working distance is reduced and the focusing range of the lens is also greatly reduced.

This is why it was suggested that you move the entire tripod and camera to get focus. In fact there are very nice focusing rails that do this for you, to enable precise focus.

I would disagree with banjo however on setting the focus to infinity, set it to the middle to allow for fine adjustment with the lens once overall framing & focus is acvhieved.

Also, use the histogram to get exposure, don't rely on metering even if it seems to work.

Mike.P® · 11-03-2009, 06:12 AM

Originally Posted by Barnster

Also is a 50mm lens a good lens to use on the end of the tubes????????

Full set of tubes on a Pentax FA 50mm f1.7. Hand held.

enoeske · 11-03-2009, 08:57 AM

Here are some shots I recently took with my smc 50mm f/1.4. I just picked up some vivitar extension tubes from keh and found a good setting to take handheld shots like this. I use f/11 - f/16 (depending on light) exposure of 1/100th to avoid camera shake and ISO 100. Then use my lumopro lp120 on 1/32nd power to add light.

Barnster · 11-03-2009, 06:14 PM

Thanks guys.I had a try without a tripod and notice that the depth of field is that shallow,that you do need a steady hand.I had the fstop at around F5.6-f8.I just keep practicing and hopefully get my shots up to par with Mike & enoeske's pics.

hoojammyflip · 11-04-2009, 02:59 PM

Check out the pentax-manuals.com website. There is a manual there for the old Takumar 1,2,3 extension tubes and bellows, which is just as relevant for any lens being moved in relation to the camera body by any tubes. It tabulates distances for the Pentax tubes and various lenses.
http://pentax-manuals.com/manuals/m4...e_up_m42_s.pdf
password is Pentax