extension tube problems

[calypsob]

I got some extension tubes today to use with a reversed 28mm pentax. It is a 49mm lens @ the filter and I have no idea the diameter of the extension tubes but they are standard $8 fotodiox tubes. I checked for light leaks and I even taped a towel around the barrel but I still kept getting the same light chunk in the center of my image. Do you guys have any idea why this is happening?


i dont get it_2 by LMNO Sunset Deluxe, on Flickr


i dont get it_1 by LMNO Sunset Deluxe, on Flickr


i dont get it by LMNO Sunset Deluxe, on Flickr

[calypsob]

the first 2 are at f/8 the second one is f/16

[Snowyman]

If there are no electrical contacts or if there are and they are not making good contact this is the kind of image one gets.

The other cause of problems with tubes is lack of baffling. The very low cost of these tubes would suggest that they lack both electrical contacts and baffling.

[calypsob]

The lens I use ordinarily is reversed and has no electric contacts either. Baffling on the other hand, is there anything I can do to remedy this problem? The tubes work fine on my kit lens but cause mucho problemos on the reversed lens

[calypsob]

Snowyman thanks alot the "lack of baffling" was the magic search word I found another thread on here that linked me to this flikr page. http://www.flickr.com/photos/johnhal...in/photostreamThe problem seems to be that the face of my reversed lens is reflecting inside of the tubes, Im still not sure on the baffling but I guess I will try and remedy both issues. Thanks again.

[calypsob]

Ok after a little more experimentation I have realized that this is caused by my bulbous reversed aspherical lens. Nothing I can do about this problem except use a normal forward facing lens unfortunately.

[Sparkeyluv]

Those don't look right