When I mounted a different lens on an old folding Polaroid many years ago, I put tracing paper where the film would lay (by disassembling an old 667 film packet). Then I unscrewed the reflector from my Mini Mag Light, leaving only the brightly lit grain-of-wheat halogen bulb visible and burnng. In a darkened room, I meticulously measured out selected distance from the film plane to the bulb, and then focused the lens until the image was sharp on the "ground glass". I then marked the focusing scale with a mark for that specific distance. Because the lens had been changed, I could't use the old focusing scale which was used pictograms anyway, but the new scale i put on top of the pictogram worked fine for my purposes. Of course, as you say, at close distances DOF is critical.
I received a mail, James from US told me that 'Actually Polaroid did make the distance scale inaccurate on purpose. What they did was based on ordinary people who are not aware 'focal plane', estimating distance between subject and the front end of lens, not knowing that real focus is on 'focal plane', about 20cm behind the lens, thus Polaroid marked the scale a little bit shorter, to compensate the common errors. When subject is far out of 5feet, that 20cm error won't bother anything, but if subject is very close, say 4feet (120cm), that 20cm deliberated shortage then become obvious! That is exactly what my curve shows me!!
And Mr.James pointed out that '110B camera was made in a closed system, that is, fixed lens, so as long as the range finder is coupled with the lens, no matter how the distance scale marked, it won't bring errors, but Byron now makes its range finder an open system, not only coupled with one lens only, and it also becomes reference for other lenses, for un-coupled setting, that makes distance scale in-correct.'
Thanks James, your explanation released me, bring back my faith to Polaroid!
Inspired by distance scale issue, I measured all lenses in hand, combine same focal length lenses into one, and plotted the curves representing them.
Most lenses marked as same focal length have same characteristic curve, except 120mm lenses I have.
One is Schneider Angulon 6.8/120mm, and another one is a vintage Tessar 4.5/12cm lens from Cocarette folder. Their characteristic curves are totally different, funny thing isn't it? That means two 120mm lenses need different distance scale.
Rules are made to be violated. I am happy to said that, since I break another rule I set before, it means the limits are less, options are wider.
Byron has its own back system, differs from International Standard Back System or Graflok Back System, because I want it to keep simple and slim as possible.
Since it did not follow industrial standard, there are some limits for those standard film holder to be mounted on.
I received feedback from my dear client Raymond, who are not satisfied when using regular double dark slide film holders: "The tabs holding the film holder do not close completely when a film holder is inserted. The tension is insufficient to keep the film holder snuggly against the camera and I am concerned that there will be a light leak. Is this how it is supposed to work? It seems you are trying to make the tabs work with all types of backs but have compromised the operation when used with a regular film holder. I think it should be the other way around - it should work perfectly with the film holder and compromises should be made when using the other backs."
What my main purpose on developing Byron camera is for hand-held, street snap 4x5 rangecoupled, so those holders who can carry as many films as possible are prior listed, Grafmatic 6 films, 120 roll films, instant film packs, to name a few, and they are all in Graflok standard, thus Byron Back System was guided for Graflok standard. Two clamps on both up and beneath side hold Graflok film holders very well, you can see operations on my YouTube video.
Trying to design a system perfectly fit both for Graflok and Graflex systems, but failed, so I had to compromise the regular double dark slide film holders, what clamps hold are only the tiny ditches on side of the holders, not very securely held. In the picture below you can see that clamps do not grip the holder by "bite in" the holder, but just hold the side by the tension.
For this I set the limits on regular double dark slide holders, only allow those holders who has ditches on side, like brand Fidelity series, or Lisco holders; and those holders who has no ditches on side are off the list, like TOYO holders.
Though clamps do not "bite in" the holder, I am not so worry, since when hand-held, your left hand holds the camera, thumb naturally press the back , providing good support of the holder, to keep it from falling.
But how about when not hand-holding, but on tripod, there is no hand to press the back, will it be secure to hold? That must be concerned by many clients who are experienced LF camera users, but seldom hand-held snaps on 4x5, like what Raymond said.
For this, I provide three options to clients to choose.
1. Keep It that Way.
If you use Fedelity or Lisco holders, with faint ditches on side, and would like to hand-held snaps, you don't need to do any change, just use the holders. When you mount the holders, your left hand thumb will provide enough press to keep the holder, and the dark slide you insert into the blocking plate (see pic, above), provides another security to keep it.
2. Make Ditches for Bite-In
If you are good at machine, and happen have tools, you can make ditches on side of the holders, let clamps grip the holders by "Bite-In", it is the best solution I can get now, but you need tools to do it. The ditch is 1.5mm wide, 20mm long, and 2mm in depth.
Here I use TOYO holders, whose side are without ditches, but with these ditches I made, they are feasible for Byron now, holders is securely hold.
3. The Velcro Way
I know that ditches way is difficult for average people, so there is an easy way, what we want to prepare are velcro tape, a pair of scissor, and file.
File both side of holder, to make room for velcro tape, you can compare original holder and the one who been filed.
Then cut the proper size of velcro tape (hook side), paste it on both sides of holder, now we provide very good "Bite-In" zone for clamps!
For comparing the "Bite-In", we list three ways in a row, you can choose an option you like. Now, the DD slide holders are not limited anymore, any holders allowed!!
Walter Garcia in NY added a bubble on Byron, how creative! I love the idea!
I should try mount one on my Byron!
Thanks, Walter, great idea!
And he successfully made ditches on side of Fuji Quickload film holder, now Byron list one more holder! Good Job! Walter!
in the mail he said
"Daniel, Attached are photos of my modification for Fuji Quick Load holder. After cutting the two small notches the fit is good. I will expose some film with this in the next few days If weather is good. It is not difficult to do but it must be done carefully and slowly. I do not have small measuring device to see exact measurement in mm. I think you can do this if you get one of these holders. They are easy to find and not so expensive. To disassemble you must remove 6 small screws circled in image #01. Then carefully take apart two half. Be careful with roller it has two small springs that like to jump out. Also pressure plate likes to fall out. The other images show where cut must be made to fit with Byron locks. Let me know what you think."
What I think? I think it is wonderful!
Walter sent me images of Quickload on the back of Byron
Looks like it is Angulon 6.8/90mm lens at work!!! That's the reason for lens interchangeable system!!
Now I took time mainly on developing Emily, WA 4x5 shooter, based on J66 body, almost the same as 110/B, except no Range finder on top, and no front door for rail, so it is a good candidate for wide angle.
All the same back system to Byron, Emily needs new bellows, new front lens plate, and a new top plate. The top plates just arrived, I installed it with two cold shoes, one for view finder, one for a tiny range finder, if uses want to, that one from Voigtlander/Cosina is good I think.
This is the position for about 47mm lens. Avoiding pig snout and helical focus ring which are popular seen on wide angle camera, I want to replace them by bellows and level, to keep it slim and easy to carry. Bellows is easy to me, but the level, that puzzeled me.
If I can successfully made it, then Emily will be a great WA camera for lenses wider than 90mm! Here I come! 47mm, 65mm!
Just brought back the top plate for Emily, I did some modification---drilled hole for bubble level. Contributed idea by Walter, drilled hole on Byron top housing, I found that Emily should have one too.
bubble level is rather thick, but thanks to the plate, it is implanted quite well
Ok, what else we need?
Kids has just re-watched Harry Potter movies, said this camera should be named "Mad Eye Moody".
Worth to think about it.
RF housing modification takes many steps, and now it adds a bubble level hole.
left to right: 110A housing, 110B housing, 110b modified Byron housing, eye window adds a eye caps attachment.
and at the right side, use putty to reshape the button line,
far right side was drilled with hole for bubble level, and a dent edge for PA-45 holder.
a lot of putty, drill, sanding, and 2 to 3 layers of spray paint.