lens blade bokeh and ground glass

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davetronic

Well-known member
i've noticed that on certain lenses, in this case the zeiss contax AE vs. MM lenses, one difference (as esoteric as it may be) is in blade design. the AE lenses i have appear to have been manufactured with what's been referred to as the 'ninja star' blade design, where the rounded tips of the blades protrude ever so slightly through the 2 stops before being wide open (it's most pronounced at 2.8 on an f/2 lens), as opposed to the smoother near circular action on MM lenses all through the wider aperture range.

i suppose this could lead to a very subtle, if not imperceptible, shift in bokeh rendering at those stops, but does the ground glass (let's say spinning in this case) negate the 35mm lens bokeh altogether?
 
i would guess at f2.8 the ground glass will negate the bokeh characteristics of a lens. I think most ggs pretty much negate a whole lot of a lenses bokeh characteristics at most f-stops, especially with vibrators where you can't stop down past f4.0-5.6. Even with spinners, the gg will do its thang to a lenses natural characterisics.

- of course the amount will vary depending upon the imaging element.
 
that's what i had guessed, although i haven't tested it. i figured the amount of bokeh variation would be miniscule when imaged directly through the lens, and that it would likely be altogether gone once you put the spinning ground glass in front of it.

if that's really the case then, in terms of lens bokeh it doesn't really seem it matters whether you're shooting nikon, zeiss, minolta, etc. etc. etc. that would be a function of the adapter.

please correct me if this isn't correct... i'll certainly post notes if i find otherwise.
 
Speaking only for our CINEFUSE imaging elements, the aperture blades will come into play at different points and we do suggest optimal apertures to get those specular highlights looking clean, and bokeh at it's best. An example would be getting the best look out of candles that are out of focus in the background.

For CF1Le/CF1: it's f4 to f5.6. Contrary to what many thought, there is very little light loss associated with doing this when using this element.

For CF2Le/CF2: it's f2.8 to f4

For CF3Le/CF3 and CFXL/CFX: it's f2.8

This little tip is the single most important I could pass on to improve bokeh when shooting night lights.
 
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