Macro tubes how to

Hi everyone i saw these on ebay http://cgi.ebay.co.uk/Macro-Extension-Tube-Ring-for-Pentax-K-Mount-K200D-K20D_W0... last night and wondered how good they were bear in mind they are about £7 delivered from china. So maybe they're not that good' but have done a bit of macro flower work and usually just use my sigma 50mm 1:1 macro lens.I have never used extension tubes before so could anyone please explain the benefits as i am totally in the dark on this subject.

Maybe these extension tubes would be ok to practice on for a while but i don't know. any advice would be much appreciated.

Extension tubes allow a lens to focus more closely to the subject. You would normally use them with a non-macro lens. As for using one with a macro lens, see http://www.google.co.uk/search?hl=en&q=extension+tubes+with+macro+lens&meta=&aq=...

I have a similar set of tubes to that cheap eBay one. It does the job, but there are no electrical or mechanical connections at all between the camera and lens, so your photograpy has to be entirely manual, and you need to use a lens with an aperture ring. More expensive sets have some connections, and possibly a more matt surface on the inside to prevent reflections.

Hi iceblinker cheers for the link it states in one of the topics from the link that some macro lenses would be suitable and some not.But the price of these they may be worth it just to get in some practice. http://www.alanwood.net/photography/extension-tubes.html

It also says that a 52mm extension tube performs like a 105mm macro lens when using a 50mm lens.How would this differ from using a x2 teleconverter on a 50mm lens?

Sorry for the lack of knowledge iceblinker Thanks for the help

I also don't have a lot of knowledge in this but so far as I know they wont work like a TC they simply able you to focus closer, they don't change the focal length.

You can see it a bit like moving a beamer further away from the screen, you see the image getting bigger. The extension tubes also relies on this so they work in almost in the same way, to simplefy it.

If you want to have 1:1 with a normal 50mm you need extension tubes with the same length so also 50mm. Since the 50mm already can focus 1:1 and you ad the same length you can have 1:2. I'm not 100% sure on this but this how I believe it works.

You already have a 2x teleconverter, if I understood it correctly the focus distance stays the same but you double your focal length so you will get also a 1:2 magnification.

I don't really see the purpose in your case to get extension tubes. Maybe if you even want to have a greater magnification you can use both of course but why would you, what do you want to archive with the extension tubes?

ps. if you read your link carefully you will see that they mean somthing else with the part I quoted from you.

A 50 mm macro lens that focuses unaided to ×0.5 covers the range ×0.5 to ×1.0 when used with a 25 mm extension tube; a 52.5 mm extension tube performs the same function for a 105 mm macro lens.
They simply show that if your focal length is twice as long you need twice as long extension tubes.

Cheers stefan it was just for my macro flower photography.when you use the 50mm you have to be practically touching the flower like in this image.Because the flowers are so small maybe about the size of your little finger nail.

[IMG]http://i669.photobucket.com/albums/vv54/sanderscapes/IMGP89041.jpg[/IMG]

I want to try and pull away from the flower but still get the 1:1 macro or as near.

I suppose i could do this by pulling away from the flower re-focussing and then crop during processing

Martin did you hand hold for this shot? to me it needs a 1/3 stop more Exp' and soft.

I put it on my P-pod.It was at f8 1/30sec shutter tried it hand held at first but no chance also there was an annoying little breeze.

This is the most that i could up exposure'anymore and i could see a lot of grain in the background.I know what you mean though it does look a little lifeless.

Is there a tool in cs3 that could correct this?

I've found this to be the case with the sigma 50mm because i am practically touching the flower with my front element.This drastically cuts down the light.

Cheers Tel

[IMG]http://i669.photobucket.com/albums/vv54/sanderscapes/IMGP88851.jpg[/IMG]

This one is slightly better but there is still something missing

Missing in what way? Focus, Exp', Colour, size.

Exposure and composition really Tel.

Not 100%.



[IMG]http://i486.photobucket.com/albums/rr227/TTKPhotography_2009/IMGP8904.jpg[/IMG]

nicer looking than mine mate what did ya do.

wonderfull shots Martin, with some postproceesing you can come close to Tel photo so keep trying.
The noise can be easly remove by a noise reduction program, Neat Image and Topaz are the big boys in that I believe.

For your lens problem, why don't you use the 2x teleconverter it will make a 100mm lens. Extension tubes will only make you able to focus closer, something you don't want I believe.

I took the freedom of photoshoping your image a bit, I hope you don't mind or else I will delete it.
[IMG]http://i282.photobucket.com/albums/kk244/Anvh/IMGP88851-edit.jpg[/IMG]
I've sharpend it, use a softlight layer and played with the levels to get this result.

not a problem stefan

I have looked at all extension tubes and I ended up with the Vivitar semi automatic tubes £40 from Ebay in that they allow you to manually focus at full aperture but auto aperture at what ever you set your f number at you can see a sample here link your DOF is critical so try to use F22 or less and a tripod.