Photoclubalpha

I have a question on screw on converters. If you attach a 2X converter to a 50mm/1.7 lens it behaves like a 100mm/3.4 lens. What happens if I screw on a 0.6X WA converter? I know the effective focal length is now 30mm. What about maximum aperture? Is it 1.02 (1.7X0.6)? Is the math linear? My intuition tells me the lens does not get faster. Could anyone throw some light on it please?

With best regards,
Sury

0.6 is for the focal length not the aperture. Any addition before or behind the lens dim the entering light (even if negligible).

Dr H is not right on this one. A genuine behind-the-lens wide angle converter is impossible, but there are converters to reduce the format - squeeze 35mm down on to 16mm film etc. They have an aperture increasing effect, exactly the reverse of teleconverters. Afocal converters, the ones you fit on the front, have no effect whether tele or wide. They maintain the same nominal aperture but may reduce light due to extra elements, of course.

David

Thank you, Dr H and David. Your prompt response is much appreciated as always.
Whether it is tele or wide, we are always going to lose light due to additional elements, that much is obvious.
What I was confused was that when Tele was used, even "effective" maximum aperture is stated as multiplied
by the conversion factor but never on wide. Too good to be true, but I thought should my glass not get faster with
a WA converter.


With best regards,
Sury

David Kilpatrick wrote:Dr H is not right on this one. A genuine behind-the-lens wide angle converter is impossible, but there are converters to reduce the format - squeeze 35mm down on to 16mm film etc. They have an aperture increasing effect, exactly the reverse of teleconverters. Afocal converters, the ones you fit on the front, have no effect whether tele or wide. They maintain the same nominal aperture but may reduce light due to extra elements, of course.

David

I didn't know that. As they say: learn as much as you can but still you'll die ignorant

Dr. H,
All it means is that some people (like me) die more ignorant than the others.

With best regards,
Sury