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12-11-2010, 02:19 PM   #1
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manual lens question and extension tubes

This summer I started getting into Macro photography after recieving a pentax macro lens!! I purchased some extension tubes off EBAY from somewhere in asia and they arent a brand name of any kind. But my understanding was I could just slap them on and my maginification would be that much better... wrong! When I put them on and then my lens I can barely see anything through the viewfinder let alone try and focus.. its just a dark grey and looks a little grainy, certaining cant see your object. What the heck is going on?? Also I read somewhere that extension tubes only work with a 'manual lens" .. whats the difference between an auto lens and a manual lens.. as I thought that the switch that went from manual to auto focus was made is an 'manual lens' ... please help !!

12-11-2010, 02:39 PM   #2
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Is it screw mount?

And it has nothing to do with focus:

You always have to manually focus with tubes. The A/M has to do with what's on your lens, and properly metering
12-11-2010, 02:58 PM   #3
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Extension tubes start simple. They move the lens away from the camera. That magnifies the image at the expense of losing infinity focus and brightness. It sounds like yours are working, sort of, because dark gray and grainy is the typical appearance of the viewfinder with tubes. They often come in sets of three, so you can change the length and magnification to suit your needs.

Tubes vary wildly in price based on how compatible they are with your camera. Cheap ones don't do anything. For a bit more, the tubes extend the aperture control lever so the camera can still stop down the lens. That maintains the ability to focus with the lens wide open. With an already dark viewfinder, focusing at typical macro apertures like f16 is impossible. For a lot more, you get electrical connections with a KA-type lens. That's handy with lenses designed for it, and a minimum requirement if your chosen lens doesn't have an aperture ring, like a DA series lens. For another big price jump, some tubes include AF drive.

It's important to match your tubes with lenses that they'll work with. The kit lens won't work without electrical contacts, and it's not very bright anyway. It's way cheaper to get a Pentax-M 50mm f1.7 and cheaper tubes than get tubes with contacts.

Your exact problem depends on what your tubes can do, then what lens you're using them with.
12-11-2010, 03:05 PM   #4
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QuoteOriginally posted by crystax Quote
When I put them on and then my lens I can barely see anything through the viewfinder let alone try and focus.. its just a dark grey and looks a little grainy, certaining cant see your object. What the heck is going on??
Extension tubes radically reduce the minimum focal distance of a lens (they create a very narrow focus zone ). For instance, on a 50mm lens with a minimum focus distance of 1.5ft distance, when mounted on a tube, becomes reduced down to about 4 inches; the depth of field becomes so narrow that you need to be pretty close to that distance when you attempt to focus.

12-11-2010, 03:09 PM   #5
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if u put a tube b4 a smc da lens u will see just darkness ( max. f value f22 f40 or what ever..)

The point is ' apreture ring '

there is a pin which controls apreture automaticly from body. when u put a extension tube between lens and body, u kill the control mechanism.

manual lenses which have manual apreture control mechanism allows you to control apreture manually thus, u need to use a lens which allows u to control apreture ring

there is another pratical solve which I always use with my smc da 50-200 lens
u can easily make an aluminium foil ball between your fingers and put it next to that control mechanism pin. it will hold it on min. value of f
this pic. will help u to see that pin

12-11-2010, 03:25 PM   #6
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I have the k100D pentax and the macro lens is the smcP D-FA 50mm f2.8. The photo tubes i bought off of ebay were just no name tubes that have about 3 pieces and they just thread into where the lens goes. So you are saying that I need special tubes with contacts?
also I still dont know what a manual lens means compared to what i have now.
12-11-2010, 03:38 PM   #7
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QuoteOriginally posted by crystax Quote
I have the k100D pentax and the macro lens is the smcP D-FA 50mm f2.8. The photo tubes i bought off of ebay were just no name tubes that have about 3 pieces and they just thread into where the lens goes. So you are saying that I need special tubes with contacts?
also I still dont know what a manual lens means compared to what i have now.
With the FA50macro you have a very good macro lens and you don't need the tubes for great macro shots.

If you want to take advantage of auto focus and auto exposure you need tubes with the correspondent contacts; those cheap ebay tubes don't have the contacts so you need to focus and meter the exposure manually.

Manual lenses comes in various types; you always need to focus manually; exposure may be automatic or not; it depends on the particular lens you are using.
12-11-2010, 04:04 PM   #8
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QuoteOriginally posted by crystax Quote
I have the k100D pentax and the macro lens is the smcP D-FA 50mm f2.8. The photo tubes i bought off of ebay were just no name tubes that have about 3 pieces and they just thread into where the lens goes. So you are saying that I need special tubes with contacts?
also I still dont know what a manual lens means compared to what i have now.
A Fully Manual k-mount lens will not have Auto Focus, nor will it have an A setting on the aperture ring. You can turn your DFA into a fully manual lens by taking the lens off of A and setting it (the aperture ring) to something else. If you have the lens set on A, then it is stopped all the way down at f22 (or whatever the highest number is) and Minimal light is passing through. The cheapo extension tubes (the $4 types) do not even have the lever to actuate the aperture.

So, What you need to do to use your current setup. Set the aperture on the lens (make sure you've set the custom menu function to permit the Aperture ring use as it defaults to not permitted) to f2.8 using the ring. The camera will not control the lens at all. Then Focus. Then stop the lens down to your desired aperture and set the shutter speed accordingly. Take your picture (a tripod would be recommended here). You now have taken your 1:1 macro to 2:1 with all 3 tubes. The Depth of field is going to be Very shallow, your viewfinder is going to be quite dark. You're going to need a lot of light on your subject to be even mildly successful. Practice, Practice, Practice. Then show us what you come up with.



12-11-2010, 04:22 PM   #9
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thank you !!! I get it now and thanks for the few of you that put it into real lamemans terms for me =D
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