Want to Buy Buy or Trade - 400mm 8x10 in Shutter

[Pioneer]

I am currently shooting my Cambo 8x10 with a 240mm lens. Love it for landscape work but would like a slightly longer lens for head and shoulders portrait work. All my 8x10 work is in B&W so coatings are not critical but would like wider aperture settings to help improve shutter speeds.

Am retired on low, fixed income so price is important. Have Fuji GL690 in decent shape that I could trade for the right lens. Also would consider trading some nice Pentax 645 lenses.

Feel free to PM with questions or options.

Thanks

 

[johnielvis]

screw off the front cell of your lens--it should convert nicely to a longer focus lens if it's a plasmat...you didn't say which lens so i'm assuming its like a symmar or some such.....at least try it and see--most of such lenses do convert and are sharp enough (particularly for portraits) stopped down a bit

alternatively--I've seen people using wollensak 15" telephoto lenses working nicely for closeups on 810...I still gotta try that myself since i got one, but from what I've seen I have no doubts that lens will cover for portraits very nicely--they are not expensive and you get a bonus of leess bellows draw...

I'd just try to convert what you have--if it works, you don't even need to buy a lenboard, right?

 

[Pioneer]

Convert

Thanks. That is a great idea if I can make it work. I do have a Schneider-Kreuznack Symmar 150 on my 4x5 that can convert but it won't cover the 8x10 circle. The only lens I own that will cover the 8x10 is my Caltar-S II 240mm. I don't think it is convertible.

 

[johnielvis]

far as I know, that caltar will convert nicely-it should be a rebranded symmar if I know my caltar names properly....maybe even right around 400mm!!!!!

even if it don't say convertable, them symmars convert
let us know how it works out

the aperture scale will be off though...you'll have to find the appx focal length and measure what the stops should be on the shutter and make yourself a secondary aperture scale for it....

 

[Pioneer]

Ok, obviously it is time to do some research. Thanks.

One small question. I have read about apertures being the diameter of the opening in comparison to the focal length but if I am going to calculate my own scale I may need some additional guidance. The way I understand this f16 on my Caltar is actually written as 240/16 mathematically. What I am not so sure of is how to calculate focal length once I figure out how to convert the Caltar from 240mm. Can you, or someone else, give me a little guidance on how to do this?

 

[johnielvis]

just focus on something at infinity and measure the distance from the lensboard to the ground glass...approximate is all that is needed..and tha'll be average between the aperture and the rear cell....there's more accurate ways but not needed for this type of work...

divide measured FL by the iris size and that's your f number

 

[Pioneer]

Focal Length

Ok, this is what happened. When I focused on an object at infinity with the 240mm I measured 9.5 inches from the ground glass to the shutter. This agreed nicely with the lens specs. With the front part of the lens removed to convert to a longer focal length (which I assumed to be the correct method for doing this) I measured 13.5 inches from the ground glass to the shutter after focusing on the same image. This came out to 340 mm (give or take a millimeter or two.)

However, the image I see in the ground glass is VERY soft and it took a lot of back and forth to feel confident I had actually focused properly. I focused on a distant tree, maybe 1/4 mile away, and with the 240 on the camera I could distinguish the leaves fluttering in the wind when I used my 8x loupe. With the lens converted to the longer focal length I could not distinguish those same leaves with the loupe. It was just a larger green mass which I knew to be leaves. I could distinguish the individual branches, but not the leaves. I am not sure that this will work out all that well for portraits.

My grandkids just arrived so I am going to try focusing on them at close portrait distances to see if this image improves at all at the much closer distances involved in a head and shoulders portrait. I'll let you know how it turns out.

 

[johnielvis]

yeah--you gotta stop it down a bit to sharpen things up for sure...hope you get something useful--for portraits though....soft focus should work better....diffuse the "ugly" details. yes stop down for sharpness...slow shutter speed...

OH...remember to focus stopped down too--there will likely be a focus shift....

I did the same with my apo symmar---360 converted using rear cell...as I recall I had problems focusing too...used it for close up portraits--it was definitely softer than the 360 all together no matter what the aperture...used strong strobes to light it up so I could stop it down.

oh well...even if it don't work , at least you learn, right?

 

[Pioneer]

oh well...even if it don't work , at least you learn, right?

That is where the fun is! That and those few terrific photos you are privileged to make in life.

Thank you very much for your help. I'll stop it down and try some portraits with it today if I can get my grandkids to sit still long enough. The len has flash sync so I'll try it with a couple of strobes.

 

[johnielvis]

great==yes---strobes are recommended---otherwise you won't know if it's blurry from the lens or blurry from movement, right?

hope you get some results you're not embarrassed to post--I'm just curious about how good/bad it looks---