Full Version: Zeiss ZM 50 f/2 on mFT
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Pages: 1 2
[quote name='genotypewriter' timestamp='1282190872' post='1901']

Hmm, not sure if I can see what you mean here. First of all, I don't think there's any more stretching of the objective plane on a non-retrofocus lens than there is on a retrofocus one.[/quote]

No, in the end there isn't, but this stretching is much more with WA lenses than with longer FLs (which is also why UWAs aren't recommended for people shots).

Quote:Secondly, if the non-retrofocus design means the nodal point of the lens sits closer to the image/sensor plane than on a retrofocus design, then it means light has to travel a shorter distance... this should, on the flipside, reduce light fall off (without considering the sensor response w.r.t. AOI).

One would expect so, but in the case of extreme UWAs, because the rear nodal point sits much closer to the sensor/film plane than it is to the edges, I don't know whether this will entirely hold. I haven't done any calculations on this, so I wouldn't really know in how far theoretical values differ from real life ones. Vignetting also depends on the size of the image circle - a good example of this is the TS-E 17. I don't know in how far, when you see examples, whether non-retrofocus (U)WAs just have a minimalistic size image circle or not - often they really show very bad light fall-off towards the edges and corners. Since they are often build as small as possible, this may actually be the case.

Quote:I agree about the high refraction within the lens due to lens design... my question is how can such a lens perform better on film than on digital but show no increases in vignetting on digital?

Three possible causes come to mind: reflections from the sensor causing all kinds of trouble (veil, flare, weird aberrations), general incident angle of the light (more effect on sensor than on film, but closer to optical axis less or equally problematic/good), and image circle size (less vignetting the larger it is).

Quote:Maybe we should think about what we haven't really talked about so far... for example film thickness and its role in reducing spherical aberrations, etc. I think even more so the reason is the magnification at which we look at digital images. You wouldn't print a 35mm slide/negative to the size of 86"x57" and look at from 2 feet away even if it was really that good, but every 12MP FourThirds image gets the same magnification on a regular 24" monitor when viewed at 100% <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='Big Grin' />


Yes, that is very true indeed. Film emulsion thickness does actually have a profound effect on a lot of things, as at 0.2 mm (and that is a thin emulsion) it is as large as the CoC on APS-C, and 2/3 of the CoC on FF. This not only allows for automatic (partial) correction of a whole bunch of aberrations, but also makes DoF transitions look different (more gradual), makes seem field curvature a lot less, and effectively makes DoF deeper than with digital. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='Big Grin' />

Kind regards, Wim
Pages: 1 2