Extreme Bokeh with the Radionar

[vilva]

In a way I was lucky when I started testing the Radionar 4.5/105 on a dSLR. I just picked a length of macro extension tube which allowed for infinity focus and a reasonable close focus, not quite the 1m of the original camera because the tube was too short for that. The characteristics of a front cell focusing lens change all over the focusing range, and my setup happened to result in a reasonably good behaviour over its focusing range.

In the original camera, the position of the lens is fixed relative to the film plane, which means that the effective focal length must change in order to allow focusing at different distances. Supposing the nominal FL is 105 mm at the infinity setting, it must be reduced to about 95 mm in order to achieve focus at the closest focusing distance of 1 m. If the lens is mounted with an external focusing mechanism, a bellows, a helicoid or an adjustable close-range ring, the focal length and the corresponding characteristics of the lens can be chosen within this range using the front cell focus mechanism, and it occurred to me that this potential might well be worth testing.

So. I mountied the Radionar on the bellows, set the front cell focus at 1 m, which felt like the most promising alternative, and began testing. For me, the best bokeh would be the Gaussian one, but it isn't always so very easy to ascertain that the bokeh really is like that when viewing an arbitrary photo. There is, however, one rather fail-safe test method: pick a nearby highlight and focus at infinity. If the resulting foreground bokeh is ring-shaped, the background bokeh will be Gaussian. So I chose a scene and got a result like this:



Well, not too good, but the rings are there. So I focused at something nearer than the highlights and got this:



quite nice Gaussian bokeh, I'd say, spheres with very soft edges

So far, so good, but what would the result be in real life? Well, it is a matter of taste - like any bokeh. What ever is said about the bokeh, the result was very illuminating. There was a glow, which at the first sight would bring veiling glare in mind, but which after some examination was revealed to be just an unavoidable result of the Gaussian bokeh, i.e., Gaussian smearing of adjacent areas - it seems to me now that the old lenses aren't necessarily so much haunted by lens flare as by the other face of their good bokeh! Here is the first example, focus at the steps:



and another one:



and a final one within this posting:



These photos remind me of the photos taken with the meniscus but with a sharper focus and totally lacking the coma of my VPK Meniscus. There is another, very important difference between these two lenses: the characteristics of the Radionar can be freely chosen between this extreme and something even past the setting I had happened to originally bump upon. The dual focus mechanism Radionar is somewhat like the old adjustable soft portrait lenses now selling for hundreds of dollars or euros.

There are more examples at http://galactinus.net/vilva/retro/radionar_uf.html

Veijo

[patrickh]

Veijo

You never cease to amaze - what a valuable asset you are for us all


patrickh

[Orio]

[vilva]