16x20 camera with 20x24 back?

[f311]

Hi all... First (or maybe second) time posting after several years here. I'm preparing to step into ULF after decades of 4x5 and 8x10. I need to build the camera for this move... a 16x20 was my first thought since it's always been my preferred display size for personal work. But now that it's actually time to commit and order a bellows for the project I'm thinking about infrequent commercial opportunities where 24" might be useful. I've heard step up backs impose serious lens focal length imitations on smaller formats (4x5 to 5x7 or 8x10 to 11x14) where the size differential is as high as 40%. But with 20x24" being only 20-25% larger than 16x20 I’m thinking a step up back would be a very serviceable solution for those instances where a little more is needed. Having never used a step-up back myself, input and suggestions from users with such experience would be most appreciated. Thanks

[John Jarosz]

How about some questions?

Is this for studio or field work?

Have you thought about the cost, and darkroom logistics?

Film holders are expensive. You will have to maintain a double inventory. Same for film. It might be easier to tape 16x20 inside a 20x24 holder rather than go thru all the work to set-up both sizes in hardware.

What kind of film? Regular or xray?

Building a camera with an add-on or changeable back requires a higher degree of precision. And the camera will most likely be heavier than without that feature. I'm fairly comfortable building things, but I built my 8x20 as a single function camera. There are structural requirements for these sizes of ULF that don't really show up in 8x10. Just getting the back (And a step-up back) flat enough in these sizes to work with the filmholders will require a major effort. For me, simply getting everything flat in 8x20 took some work.

If this is for field work, then transporting all this stuff will be a challenge. 20x24 almost requires it be made onto a cart rather than a tripod. These sizes work very well as kites when outdoors.

Yes, once you get to these sizes there should be lenses that can accommodate what you are looking for.

Are you currently enlarging images to 20x24 from 8x10? IOW, is your darkroom already sized for 20x24?

Not really any solutions, just some thoughts.

John

[Randy]

This is something I am in the very early stages of contemplation. I shoot 8x10 X-Ray film strictly for contact printing cyanotypes...occasionally silver contact printing. I have wanted to go larger as cheaply as possible, so I recently purchased a singe 8.5"x15" film holder and my intention is to build a step-up back for my 8x10 F&S. Preliminary calculations seem to be that the back step-up box is going to be about 6-7" deep at most in order for there to be no vignetting.

[Monty McCutchen]

Pm if you like. I shoot a 20 X 24 camera with a 16 X 20 reducing back. Came at it the opposite direction than you. I use the format for Pt/pd and pt/pd gumover a and wet plate collodion ambrotpyrs and alumnitypes


I'd be happy to answer your questions. John speaks the truth but that doesn't mean you can't do it it just means you have to really WANT to do it.

Best

Monty

[f311]

Thanks for your time. You bring up very important considerations John.

The camera will be strictly for field work and at full sizes wetplate only. I do plan to make an 8x10 back at some point for film. I too am comfortable building and my basic design is deardorff inspired. It will be more work than a T frame or the classic extension rail type but quickest setup and breakdown (if you can call 16x20 quick) plus a self containing unit is paramount. Aside from the bellows I'm building everything including the large film holders.

My film only darkroom can handle 4x5 to 8x10 that I then scan or contact print but I an building a darkroom box with many yards of commando cloth for the larger wetplate work.

If this was to be used for strictly personal work I would not consider larger than 16x20 but my notion about sometimes needing 20x24 stem from the idea of shooting on location family portrait tintypes or glass negs, centerpiece items that I expect may need to be a little larger than 16x20.

I've never shot larger than 8x10 but I image 16x20 is about the real limit for field portability. I'm definitely not interested in a ULF that needs to be wheeled around.

I've picked up a few lenses on ebay that will cover the formats at least at small stops... 7a Dagor and TTH Process lens.

[Oren Grad]

More thinking-out-loud: Sketch out the geometry to figure out how much extension your envisioned expansion back is going to need, think about how much it's going to weigh, then add the weight of the 20x24 film holder that will be inserted in the back to make a picture.

Now think about how robust the construction of your rear standard is going to have to be to safely hold that weight. Consider not just the structure itself but also any retaining clips or other means of attaching the expansion back, how robust they will need to be and how securely they will need to be anchored.

My bias is that using a 16x20 reduction back on a 20x24 is going to be far safer - more physically robust, less prone to operational hassles and less risk of catastrophic failure - than using a 20x24 expansion back on a 16x20. But even 16x20 is beyond what I can handle as a field camera, so when I'm doing the reckoning I'm assuming a camera that will stay put in the studio, so that the size/weight penalty of using 20x24 as the base camera doesn't matter.

[f311]

More thinking-out-loud: Sketch out the geometry to figure out how much extension your envisioned expansion back is going to need, think about how much it's going to weigh, then add the weight of the 20x24 film holder that will be inserted in the back to make a picture.

Now think about how robust the construction of your rear standard is going to have to be to safely hold that weight. Consider not just the structure itself but also any retaining clips or other means of attaching the expansion back, how robust they will need to be and how securely they will need to be anchored.

My bias is that using a 16x20 reduction back on a 20x24 is going to be far safer - more physically robust, less prone to operational hassles and less risk of catastrophic failure - than using a 20x24 expansion back on a 16x20. But even 16x20 is beyond what I can handle as a field camera, so when I'm doing the reckoning I'm assuming a camera that will stay put in the studio, so that the size/weight penalty of using 20x24 as the base camera doesn't matter.

This is a very good idea. If a scale drawing furthers the notion of design feasibility I can always reduce weight and lessen operational risks by using a lightweight wood like cedar for the expansion back. I still want to message Monty to get his take on using a full 20x24 camera as I know operationally that is the better choice.

[Fr. Mark]

May I suggest you make a full size drawing and possibly a cardboard mock-up? Even people good at reading engineering drawings are sometimes startled at how big and unwieldy things are full size, compared to a 2D flat drawing. I'd contemplated going from 4x5 directly to 14x17 and might've if I'd realized what a 1 diopter close-up lens can do...but drew a full size 8x10 and was stunned at how big it is. One of these days I will build version 4 (and 5) of the 8x10 and may some day build or buy whole plate and 14x17. Or finally convince myself I can live with scans of small format negatives like 4x5 and 5x7 (whispers: or even smaller...).

[Monty McCutchen]

Been incredibly swamped!! I haven't forgotten you. I want to answer meaningfully though and will have that opportunity probably Thursday. Hang in there with me!

Monty

[f311]

May I suggest you make a full size drawing and possibly a cardboard mock-up? Even people good at reading engineering drawings are sometimes startled at how big and unwieldy things are full size, compared to a 2D flat drawing. I'd contemplated going from 4x5 directly to 14x17 and might've if I'd realized what a 1 diopter close-up lens can do...but drew a full size 8x10 and was stunned at how big it is. One of these days I will build version 4 (and 5) of the 8x10 and may some day build or buy whole plate and 14x17. Or finally convince myself I can live with scans of small format negatives like 4x5 and 5x7 (whispers: or even smaller...).

Good call and yes, I did draw full size side and rear views about 2 months ago and it’s quite exciting. From the time I started with my first 4x5 back in '86 I desired a camera that would allow a 16x20 contact print but I rationalized and convinced myself time and again 4x5 is enough. I added 8x10 for a while in the middle but stuck with 4x5. And for much of what I've done to date, it has been enough. For years I made enlarged negatives and coated my own pt/pd and cyanotype. I never, ever considered wet plate until rather recently but now that I’ve tried it in 4x5 I have fully embraced the idea of coating my own large plates and suddenly a 16x20 camera would not simply satisfy a desire but serve a very real purpose.

[f311]

Been incredibly swamped!! I haven't forgotten you. I want to answer meaningfully though and will have that opportunity probably Thursday. Hang in there with me!

Monty


No rush, when you have a chance Monty. Since I pm'd you, I've had the opportunity to read several of your helpful and insightful posts elsewhere on the forum and seen some of the beautiful work you create with your ebony 2024

[Fr. Mark]

An Ebony 20x24? Whoa! Can we see pictures of that? With a human next to it for scale? What does that weigh? What do the lenses weigh that do justice to the camera?