Re: [Leica] comparison of Hologon and Heliar lenses

[Godfrey DiGiorgi <ramarren@bayarea.net>]

Thank you for the compliment. 

I agree: it's hard to evaluate things based upon an image given the
derezzed nature of a typical web image. That's why I consider the test
to be casual at best, not a rigorous study. 

The enlarged sections of the negative are actually the native 2700 ppi
pixels fitted 1:1 to screen resolution without dithering or interpolation.
They show all the information visible with a 2700 dpi scanner, and I tried
to choose sections of the negative which were not into the toe of the
film's response curve. 

Exposure varied a little bit between the Contax G2 and the Leica CL since
I didn't use an external light meter, that's why I'd not want to make the
assertion that one makes better shadow detail than the other. It does seem
that the Hologon has a more pronounced central hotspot, though, when I
look at a group of photos on average. This is probably due to the fact
that the Hologon projects about 5mm deeper into the lensbox of the camera
than the Heliar: that closeness to the film plane can account for the
increased falloff due to the inverse square law. I was worried about
clearance for the CL's meter arm with the Hologon; with the Heliar, it's
just not an issue at all.

While the Heliar does have a wide aperture range, it doesn't necessarily
mean that it's all that useful. Diffraction effects start to intrude
significantly on resolution after stopping down much further than f/8, the
actual aperture at f/11 is only 1.3636... for a 15mm lens. I'm curious
enough to want to explore this a little bit.

The Heliar is indeed a brilliant lens for a very modest amount of money.
I'm glad I bought it rather than modify the Hologon.

Godfrey

> Thanks for a great comparison.  While it is hard to be positively
> critical when viewing an image on the computer, it is clear by the
> enlargements that the Heliar is certainly a great value, and seems to
> me to be the equal of the Hologon in many ways.  Indeed the light
> falloff seems BETTER in the Heliar.  Add this to the price and the
> much more usable aperture range and I think the Heliar is a steal