Want to build a portable zone focus camera for a Schneider 58mm super angulon

[kanishka]

Hey guys, I want to build a 4x5 portable camera for street portraits. My idea is to have a fixed focus zone.

Subject distance 80 cm
f:22
Depth of field
Near limit 53.4 cm
Far limit 159.7 cm
Total 106.3 cm

I will make a 3d print of a basic black box.
How can I calculate the exact distance between the lens and the film plane for this?

[Pere Casals]

Hey guys, I want to build a 4x5 portable camera for street portraits. My idea is to have a fixed focus zone.

Subject distance 80 cm
f:22
Depth of field
Near limit 53.4 cm
Far limit 159.7 cm
Total 106.3 cm

How can I calculate the exact distance between the lens and the film plane for this?

You have to depart from the Flange Focal Distance (FFD), find that in the datasheet. When you set the FFD between the film and the flange that's in the rear of the shutter you have lens focused at infinite, and the Rear Nodal Point of the lens is at 58mm (or what actual flocal length you have) far from film, sometimes real Focal Length is a bit different from the commercial number.



Then you have to calculate the bellows extension that you have to add to the FFD to make the camera focus at 800mm, you can use this formula (https://www.largeformatphotography.i...l=1#post628925)

The formula 1/F = 1/D + 1/E works for thin "ideal" lenses, this is when the rear and the front nodal point are the same point, "non thin" real lenses have two principal nodal points . For calculations in real lenses you use distance from film to the Rear Nodal Point and distance from Front Nodal Point to subject, if subject is very far then we can simply consider that the Front Nodal Point is the lens front.

So 1/58 = 1/800 + 1/Extension

0.017241 = 0.00125 + 1/Extension

0.017241 - 0.00125 = 1/Extension

0.015991 = 1/Extension

1/0.015991 = Extension

Extension = 1/0.015991 = 62.5mm


Well, imagine you set your lens at the FFD, have focus your camera at infinite, and your Rear Nodal Point is at 58mm from film, but it has to be at 62.5mm to focus at 800mm, you have to have to extend 62.5 - 58 = 4.5mm more, so you have to place the flange of the rear of the shutter at the FFD+4.5mm.



In practice, you take the lens position to focus at exactly infinite and then you extend exactly 4.5mm to focus at 800mm. Those 800mm are from the Front Nodal Point to subject. That Front Nodal Point is "usually" inside the front cell of the lens, but datasheet may say where it is exactly.

Check it in practice, and provide a way to shim the lens position, from a shorter than required to longer than required.

[kanishka]

Super clear info, thanks Pere!

[Tin Can]

I would add a fudge factor, that allows adjustment.

Perhaps a currently affordable M65 to M65 17mm-31mm Adjustable Focusing Helicoid Adapter 17-31mm Macro Tube, there are other smaller sizes.

I have one coming soon...

[kanishka]

I would add a fudge factor, that allows adjustment.

Perhaps a currently affordable M65 to M65 17mm-31mm Adjustable Focusing Helicoid Adapter 17-31mm Macro Tube, there are other smaller sizes.

I have one coming soon...

Yes that would be good, something like travelwide camera.
What lens are you going to mount to the Helicoid Tin Can? Not sure how to adapt it to fit my 58mm

[Jac@stafford.net]

I would add a fudge factor, that allows adjustment.

Perhaps a currently affordable M65 to M65 17mm-31mm Adjustable Focusing Helicoid Adapter 17-31mm Macro Tube, there are other smaller sizes.

I have one coming soon...

I hope your Heli adapter is better than mine from China. They used a lubricant that made it impossible to turn.

[kanishka]

I found someone that made exactly what I was looking for http://ivancak-cameras.com/
Just a simple 3d printed box with helicoid

[Tin Can]

Don't know yet, I will experiment. I bought the 65mm as it seem less popular than smaller sizes and I didn't want to miss a good thing.

I calibrated my TravelWide to 5 ft with a Wolly 90mm and that works well for me.

I guess the 5 ft distance, use flashbulbs, handheld.


I add a heavy QR plate to the too lightweight plastic camera so I can set it down easier.

I treat it very carefully, like eggs... but more so

I think most people broke theirs.

Yes that would be good, something like travelwide camera.
What lens are you going to mount to the Helicoid Tin Can? Not sure how to adapt it to fit my 58mm

[Dan Fromm]

OP, I just checked your calculated DoF numbers. More exactly, I put 4x5 film, 58 mm focal length, f/22 and subject distance 80 cm into the calculator at dofmaster.com.

It returned the numbers you posted, also told me that the circle of confusion's diameter is 0.1 mm. I don't know where the person who wrote the calculator got that CoC, but it seems a bit large for anything but contact printing.

If I were you I'd reconsider how much DoF you'll get with a more realistic CoC before proceeding. And unless I were dead set on making the camera myself I'd look at this: https://www.maleficwares.com/malefic-4x5

[Tin Can]

Dan have you seen any reviews of that company? Or products?

I have not, but that name and Logo scared me off.

They also have more legal doublespeak than any company I would use. Yes, I know that word is newspeak.

OP, I just checked your calculated DoF numbers. More exactly, I put 4x5 film, 58 mm focal length, f/22 and subject distance 80 cm into the calculator at dofmaster.com.

It returned the numbers you posted, also told me that the circle of confusion's diameter is 0.1 mm. I don't know where the person who wrote the calculator got that CoC, but it seems a bit large for anything but contact printing.

If I were you I'd reconsider how much DoF you'll get with a more realistic CoC before proceeding. And unless I were dead set on making the camera myself I'd look at this: https://www.maleficwares.com/malefic-4x5