convertable lens

[allsystemsfail]

I'm looking at a schneider kreuznach symmar 300/500 5.6 convertable lens, and my question is do I have to use a yellow or orange filter when shooting it converted? And what about with trans. film?

Rich

 

[removed account4]

I'm looking at a schneider kreuznach symmar 300/500 5.6 convertable lens, and my question is do I have to use a yellow or orange filter when shooting it converted? And what about with trans. film?

Rich

hi rich

i have a 210-370 symmar.
i have never used a yellow / orange filter ( don't even own one )
shot chromes, b/w and cn -- never had a problem.
like everything, you will hear a variety of opinions, and as always YMMV

good luck

-john

 

[Ole]

It depends a little bit on how much coverage you're trying to squeeze out of it.

Using a 300/500 as 500mm, at infinity focus, on 8x10", there will be a little bit of chromatic aberration in the corners. I haven't tried that just yet, but I've used a 150/256mm converted on 4x5". For large enlargements (say more than 8x) I would definitely recommend a filter for BW. Smaller than that, I don't bother.
Using the 180, 210, 300 or 240 I have on 4x5" it's not needed. Same with the 240 or longer on 5x7".

 

[photobum]

I think it's just another one of those test and see situations. I have a bunch of convertibles. The most beat one is a old Wollensak triple 13-19-25. The rear 19" element has some seperation. Looking from the rear it would seem that at f/16 you clear the seperation. I always use it for 8x10 and that's contact printed so I never worried about it.

A couple of weeks ago I was looking through some old negatives searching for some "mill" photographs. I found one that did not work as photographed but as a 4x5 crop it was just what I was looking for. So I chopped up the negative, lower right hand corner being what I was after. At 16x20 I was blown away be how sharp, detailed and the contrast that the old Wolly could produce. And this was out at the edge.

AA used converted lenses all the time and he was known to print big. Me, I tend to use a filter when converted. Hey, for two sheets of film you can test your own lens and know for sure.

Hang out at some workshops and you will always find some guy with a $5,000 camera and a bag full of $1,500 lenses. They never seem to have any finished prints...

 

[johnnywalker]

Would someone explain the theory of why a filter might be useful on a convertible lens? Just curious.

 

[Ole]

I mentioned chromatic aberration in my previous post, and that's why.

Converted lenses tend to have a bit of chromatic aberration, which means that different colours won't focus in the same place. Eliminating some colours will make the picture sharper.

On the other hand, filters do nothing at all for zonal aberration, spherical aberration, coma, or astigmatism - all of which are usually worse than the chromatic. So I don't bother with a filter.

 

[johnnywalker]

Thanks Ole.

 

[sanking]

I used a Symmar 360mm convertible for several years and, although this lens performed reasonably well in the center with a single element, performance at the edge of the field was seriously degraded by aberrations, and of these the most serious was lateral (transverse) spherical aberration. The result of this aberration is that light of different color is different in size at the pont of focus. You can see this by looking at the groundglass at the edges and you should see a kind of rainbow look.

Stopping down does not improve LSA. What you need to do is use a filter that will block the color that is most different in size. Usuallly Red and Green light is closer in size than Blue, so you probably want to block the Blue. A yellow filter is effective for this, an orange one even more effective.

Sandy King

 

[DrPablo]

I'm looking at a schneider kreuznach symmar 300/500 5.6 convertable lens, and my question is do I have to use a yellow or orange filter when shooting it converted? And what about with trans. film?

Rich

I have the same lens. When it's not converted, it's beautiful and sharp.

On my 4x5 (even with a total 560mm extension monorail) I don't have enough bellows draw to convert it using the rear cell; so I've shot using the front cell alone at 500mm. It's reasonably sharp with a color filter, but not quite as good as at 300mm (though you're ideally supposed to use the rear cell).

On my 8x10, when I've converted the lens (using the rear cell alone this time), I've actually seen very broad chromatic aberrations projected on the ground glass (quite an amazing thing to see at that size). But stopped down and with an orange filter it was extremely sharp (on an 8x10 contact print).

 

[Jerevan]

I've only heard that a yellow filter would cure the slight focus shift one might get with a converted lens. But I haven't tried it (don't have enough bellows draw on my camera) so take it for what it is - hearsay. Looked it up and AA says in The negative, p. 53: "Focus shift may be due to spherical or chromatic aberrations; in the latter case it can be corrected by using monochromatic filters, but perhaps at the expense of unwanted filter effects in the print values."

 

[Ole]

since this comes up every once in a while, I dug out an old picture shot with a 150mm Symmar, converted, on 4x5" Ektachrome. Since it has to be BIG to show the aberrations, I put it on flickr:

http://www.flickr.com/photos/71733804@N00/438377619/

The fine detail in the trees show the aberrations very well, but as you can see it must be printed very big to be objectionable.

 

[Ole]

The full scan is 2780x2050 pixels, if anyone really wants to see it send me a PM.