Vignette effect?

dirtyleo

I am trying to reverse a 50mm on a 28-135mm,the adapter ring having a 20mm differential from 52mm on the 50 to 72mm on the 28-135 is causing a great amount of vignetting(I think).The reasoning behind this is that the surface area of the 72mm diameter lens has been reduced by 10mm on each side thus blocking any reflective light entry from reaching the elements in the 28-135.The resulting image appears as if a pic was shot thru a hole in a piece of cardboard ,thus giving the severe vignette effect.

Now if some one were to agree with me,tell me so, then I can move forward and be happy but if you tell me I'm all wet then you have to tell me how to combat this vignetting or that these two lense are not compatible in the reversing world of macro.

I hope I have stated this scenario clearly.

dick

GOLDENORFE

it does sound like you are correct, you will just have to compose to crop correctly.
phil

dirtyleo

,not much to crop I cannot get enough subject to crop ie: I can only get about 1/3 of a quarter(coin) in the clear.

dick

GOLDENORFE

have you tried just reversing the 50 direct onto the camera ot ex tube?

dirtyleo

Its not a problem with the 50 I have done several pics with it reversed,this all started with the 28-135.I just tried the 28-135 with the tube,set the pointer in the middle of the macro scale and got nearly a full frame with a quarter(coin) at about 5 inches working distance,no vignetting.I still think its the big diffeence in lens diameters.

dick

Capularis

Is the aperture of the reversed 50mm wide open and the focus set at infinity? If you still get vignetting then you can try adding an extension tube to the 28 - 135mm.