What lens do I need for my process camera?

[alexchem]

Hi! everyone. My first post today. I really enjoy this site.

I have an acti 25 process camera that I use now for makeing 4x5 and 8x10 transparencies. It works great but now I have art to shoot that is very large- the last one 60" x 57", and I want to make 4x5 and 8x10's of it, and even larger ones too. I have figured out a method to mount the art, but I don't know how to get the image down to the 4x5 size. It's like 6-8 per cent of the original. I have a 12" and a 19" rodenstock apo ronar lenses. What do I do? Please help!!

[Dan Fromm]

Alex, pardon my ignorance. How much extension does your camera have and what is the greatest film plane-to-subject distance you can get?

To give you an idea of what you're up against, at 0.06:1, film to subject distance will be 18.75f. So with a 12" lens the subject will have to be nearly 19 feet from the film plane. If you know how much space you have, you should be able to figure out the focal length needed.

[alexchem]

Ok, how did you do that? You're a genius! The bed is about 12 or 13 feet, and the mounting board is about 4' x 5' and very heavy, so I can't take it off very easily, and it will throw my parallelism off. All I have is the markings on the bed and one of those wheels to determine percent of original. I thought of taking it off and doing portraits too. I can't figure out what to do to gain the distance, The length from lens to subject is about 11 feet.

[Dan Fromm]

Alex, I'm absolutely positively not a genius. Idiot is more like it. But I did learn the basics.

If the bed is 12', then 18.75f = 12' and f = .64' = 195 mm. What matters for you is film to subject distance, not lens to subject.

[lenser]

Hi, Alex.

If your camera is on a flat floor and can be moved, and if your walls are perpendicular to the floor or even close to it, then you can mount the art (flat) to the wall and you have no issues with film and art being parallel. At farther distances, any very slight tilt irregularity will become negligable, or if you can tilt with the back or the lens as on a regular view camera, you can cancel out any slight tilt of the subject by matching the angle on the film.

Even with your current lenses, you may be able to back the whole rig away from the artwork far enough to get the image size you want. As Dan says, it's the film to subject distance that matters. If you can't back far enough away, then you do need a different and shorter lens.

Good luck.

Tim

[alexchem]

Ok, thank you. I am ashamed to have completely forgotten the math. You have brought an important point up to me which I knew I would have to address sooner or later. I need to go back and learn all about this.

Could I then take a telephoto from my Nikon 35 and mount it on a lens board and use it to accomplish the shot? I have to make do with what I have. I suppose it would need a long exposure but I have some big strobe units. Alex

[alexchem]

Tim,
I think you have hit on something too, I can remove the bellows camera piece from the bed as a separate object as long as I mark the position carefully and shoot right from a wall. I would be turning the camera into a very big view camera. That might be exactly the way to go. That would be a permanent solution for the future. I can increase the film to subject distance to 50 feet. I could make the bed portable. That would work. I am very happy I found this resource. Thanks Alex

[Dan Fromm]

Alex, I gave you a very strong hint. You can do the job with your present camera set up as it is if you get a 150 mm or 180 mm process lens. Think 150 G-Claron or Konica Hexanon GRII or Eskofot/Intergon/Staeble.

I don't think a 150 Apo Ronar has the coverage you need.

A 180/9 Apo Saphir will probably do too, if you can find one.

At the magnifications you're working at, I doubt you need to use a process lens. Any decent modern 6/4 plasmat type 150-160 mm taking lens for 4x5 should work for shooting 4x5s.

If you want to shoot 8x10, you'll be shooting at around 1:6 and film-to-subject distance will be around 8.2f. I'm not sure your 12" Apo Ronar will cover 8x10 at 1:6, but if it will you're set. Your 19" Apo Ronar is a little too long.

A tele lens that fits a Nikon SLR won't have anywhere near the coverage you need.

[alexchem]

Remember Dan until last year I only had hope that someday I would have a large format camera. I never had the money. Then this came along and I want to do everything at once. 40 years of ideas and dreams that now I can do at least for a few more years. I really appreciate all the input. I would like to shoot very large pieces, on 8x10 or larger if I can find the film, then scan them into digital and print hi res mega prints maybe 20 feet high by 40 feet long- in strips 44" wide. That's the plan and dream. At least one of them. Alex

[Dan Fromm]

Alex, like me you need a better education. Reading the LF Home Page's articles on starting out in LF is a start. You might also buy a book or two, much advice about which book has been posted here already.