View Full Version : Sironar N as convertible?

Paul Schilliger
3-Feb-2004, 03:00
Does anyone know if one can expect good quality for color work from a Sironar N (the longer ones) used with a single lens cell? Is there any other lens that would make a decent and reasonably big 900-1000mm (36-40") when used that way? Would the quality beat that of, say a 600mm shot on rollfilm?

steve simmons
3-Feb-2004, 08:35
Does anyone know if one can expect good quality for color work from a Sironar N (the longer ones) used with a single lens cell? Is there any other lens that would make a decent and reasonably big 900-1000mm (36-40") when used that way? Would the quality beat that of, say a 600mm shot on rollfilm?

--Paul Schilliger, 2004-02-03 02:00 AM ........................................................................................................................................................................................................................................................................

These were not designed to be convertible lenses. All lenses have a front and rear cell. Part of their job is to correct problems caused by the other. When you remove the other you remove the fixes. This is why convertible lenses really never worked very well.

Nikon makes a telephoto lens in the 600, 800, and 1,200mm range. The front cell stays in place and the rear one is changed depending on the desired focal length. There are Dagors and Artrs in the range you are looking for as well.

steve simmons

Thilo Schmid
3-Feb-2004, 09:40

modern lenses are more complex in design. The different glass types are carefully in tune with each other. Removing one cell will e.g. cause severe chromatic aberrations. Anyway, it would be difficult to handle a bellows extension of 1 m. You might as well take an umbrella to catch the wind...

Armin Seeholzer
3-Feb-2004, 11:48
Hi Paul

I will do a test in spring with my Sinar P and F together to get my 360 N only with front and also only with back elements. Will give me around 720mm I also will do the test with my APO Ronar 480mm but it will not be bevor May! But I let you know!

Paul Schilliger
3-Feb-2004, 16:10
Thanks guys, some good points.

I was aware of the things you mentioned, but as a pragmatic guy, I always like to try it first or listen those who tried. The Sironars N are not designed to be used as convertibles, and although they are probably not usable on their entire field, maybe they would work decently on 4x5", knowing that the format will only use the sweet spot of the much wider field of the lens. Or maybe they would just produce a terrible image. I doubt nobody has tried. Bellows should be around 700mm for a 480mm Sironar front cell. Some modern lenses work quite well as single cells although they are not advertised as such. Armin, I have tried to use a Ronar cell, but they are no good at that. The Apo lenses such as Apo-Symmar are no good either, but thanks!

Ted Harris
4-Feb-2004, 16:18
Sevewral years ago I was pressed into shooting my brother-in-law's wedding at the last minute. I did the formal shots with a 240mm Symmar-S MC. It was really was last minute and I was running like a chicken without a head. To make a very long story short I got fuddled and forgot to put the rear element back on the lens. Shooting with the front element only I got some fine results. My guess is that my focal length was about 360 or so. Resolution was fine for wedding work.

Totallyunplanned and unscientific but it did work.

Paul Schilliger
4-Feb-2004, 16:42
I'm sure there could be some good surprises! If it works, the major draw back would probably be the T22 opening of the original f8,4 lens. Very difficult to work on such a dark ground glas without a bino viewer.

Armin Seeholzer
15-May-2004, 17:38
Hi Paul

I tried the convertibel test with my Rodenstock APO Sironar N 360mm so the back element had a bellows lenghs of 42 cm at infinity and I had to stop down to f 11 for focusing because full open it was to soft so it could give a good portait lens! At f 16 it was usefull but behind a normal lens! Now the front element was so soft fully open and I got a bellows extention of 85 cm and at f 22 it started to get a bit sharper so not a solution for your dreams, but could be a good lens for "fuzzi wuzzis" as AA stated over the Softfocus lens users! So I use it again only as heavy 360mm for my 8x10 Sinar and almost in my studio!

Paul Schilliger
16-May-2004, 01:41
Hi Armin,

Thanks for the report! I would have expected that poor results from an APO design. The same occurs with the Apo-Symmar line. They are very different lenses than the pre-Apo lenses such as Symmar-S or Sironar. Still if someone would try and report on using a Sironar post-convertible, but pre-Apo as a single cell, it could be interesting! Thanks!

Cheers, Paul.

David A. Goldfarb
7-Nov-2005, 09:58
Not exactly the question originally asked here, since this is a shorter lens, but I recently replaced the 135-235mm/f:5.6-12 Symmar convertible in my backpacking kit with a 135/5.6 Caltar II-N (Sironar-N), and just ran a test to see if it might be suitable as a convertible for a trip I'll be making with it in a couple of weeks. The rear cell alone is about 230mm, f:11. Wide open it's a portrait lens, but stopped down 2-4 stops it's not too bad. The optimum aperture, judging from what the image looks like with a 6x loupe on the groundglass is 3-4 stops from wide open.

Here's a test on Type 55 (neg scan), EI 40, with the lens set at f:16-2/3 on the scale (so approximately f:32-2/3), 1/2 sec, no filter, on an 8x10" Sinar P with 4x5" back and a compendium shade. Detail is at 1000 ppi.


For B&W a strong monochromatic filter should sharpen things up noticably.

Kerry L. Thalmann
7-Nov-2005, 11:43

Did you do a side-by-side comparision between your convertible Symmar in single cell mode and the Caltar II-N/Sironar-N. I'm curious how the performance of the two compare in converted mode. In other words, is the older lens that was designed to be used as a convertible any better, in the single cell mode, than the newer lens that is optimized for use in two cell mode and not intended to be used as a convertible?


David A. Goldfarb
7-Nov-2005, 12:02
I didn't do a side-by-side comparison in the converted mode, and I sold the Symmar, since my main use for this lens is as a 135mm, and the newer lens is clearly better than the older one in the unconverted mode.

That is an interesting question, though. My impressionistic sense is that they aren't too far apart. I notice the focus shift more with the Caltar II-N than I did with the Symmar, and if memory serves me correctly, the Symmar is maybe a bit sharper wide open, but I don't know that there would be a big difference stopped down 3-4 stops, where I would likely be using such a lens in practice.

I just read in another thread that the original convertible Sironar was designed to be used with the front cell alone, rather than the rear cell, so another interesting test might be to compare the results with the front to the rear. It would certainly be more convenient to use the front cell with less bellows extension, ability to mount filters and a shade on the lens, and no risk of losing the shim from the front cell.