110B camera was designed for 127mm lens, it's flat bed has 20mm of rail moving range, enough for 127 lens to focus from infinity to 3 feet.
Now we are planning to use 150mm lens on it, 20mm range just makes150 lens focusing from infinity to 5 feet, I tried to extend the moving range flat bed, but fail, because the arm connecting the lens cam is not able to extend any longer.
That makes 20mm rail very precious, we should utilize all the range on focusing purpose.
When lens focuses at infinity, it gets shortest distance from lens to focal plane, and then distance added when focusing near objects. So we need at least locate the i.stop position for 150mm lens on flat bed, then utilize the rail movement for object within range.
But the bed is so long to accommodate all 150mm lenses' i.stop, some 150 need little more extension for infinity stop. Previous post has discussed about this situation before. (We will discuss about variety of 150mm lenses later).
Images below shows some i.stop for 150 needs no extension, but some need about 4mm of extension to achieve the shortest distance.
4mm of rail movement for i.stop, means that focus range will be shrinked from 5 feet to maybe 6 feet, which is, definitely not tolerated.
The solution? we should try to make 4mm extrudes of the lens when mounted, so to keep the precious full 20mm rail movement on focusing.
So here is the answer, besides normal lens board, there are extruding version.
That complicates the parts we need, but it worth it, because not only it solve the 150mm lens problem, it also allows us to use #1 shutter on Byron.
Extruding ring makes #1 shutter avoiding the collision with struts. Next time I will try my Angulon 6.8/120 on Byron!!
Image below shows Heliar 4.5/15cm lens on Linhof #1 shutter, from Prof. Don, when the lens arrived I measure the shutter, it is OK to mount on normal lens board, but struts on both sides makes operation awkward, but now with this extruding lens board, not only solves the i.stop location problem, also makes this big shutter operates easily and cozy.
Do you see it? Don?
Last edited by salihonba; 01-01-2010 at 08:18 AM. Click to view previous post history.
Analyzed some 150mm lenses on Byron, detail in my blog.
Conclusion, best choice: Rodenstock Geronar 5.6/150, reason: can stay in camera when fold up.
secondary: Fujinon.W 5.6/150 (old version), reason:directly mount/un-mount
Each Byron is converted by clients request, especially for the lenses they picked. Different combinations of brands and types of lens, shutter, it definitely needs each lens' infinity stop be measured specifically.
After individual measurement for each lens, then the i.stop engraving need help by my mechanist.
A special T type lathe knife was ordered.
The knife will engrave the plate a 1 mm width ditch, to keep and hold the front standard. Measurements are precised down to 0.01mm, with a CNC lathe machine, that will do the job very well.
And now my mechanist will make a fixture tooling, to hold the plate in fixed position.
Fix the plate in vertical position, and lathe tiny ditch according the measurements.
Then the plate is engraved the focal length by the ditch, for identification. I need some more practice of engraving......
For my own reason, to ensure pairing the plate with matched camera body, I engraved each owner's name on the back of the plate.
Then the installation, and rechecked the focus. Noticed that 90mm lens distance scale at the right side? that is for un-coupled focus.
Try to mount a Xenotar 2.8/150 lens on it, really a big fellow!
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The closest distance of subject is about 3.5ft.
Byron + Xenotar 2.8/150, f/2.8 1/200sec, Fuji FP-100C 4x5
All focus as close as possible (3.5ft), I found that DOF is really shallow, wasted about 4 instant films to get these two rather satisfied results.
150mm, f2.8, focus at 3.5ft, DOF got only 0.08 ft (2.4cm!), means when I focus at the eyes, ears are already out of focus!
and I had not made the lens coupled with range finder yet, I made photos this afternoon by gg panel, ruler, and ordered my kid to hold still, not even breath!
Last edited by salihonba; 01-14-2010 at 09:46 AM. Click to view previous post history.
That's 24mm, not 24cm. 24cm of DOF would be quite a lot (about 9.5").
Originally Posted by salihonba
I received feedback from Raymond who told me that "the focus scale, the ground glass and the rangefinder did not agree on the focus distance." That brings me curiosity how precise the RF on 110B? I never doubt about the distance scale that camera shows me, until this time.
So I managed to measure the REAL distance scale that read out from ground glass panel. After some cameras were measured, a curve plotted to represent the relationship of focus distance and the rail movement.
Black curve represents the measure I made from ground glass, the blue curve is what distance scale on camera marked.
The curve tells me some facts that I should let all of the polaroid 110A/B owners to know, that is "the distance scale on camera is IN-CORRECT"!!
How surprise! I did trust the credits of Polaroid, their reputations of the quality control on productions......., but I should check before that!!
The curve tells me that 127mm lens actually can not focus as close as 3 feet, like the distance scale shows, 3.6ft (110cm) is the nearest distance that camera can focus.
And the curve tells me more, that the distance scale is somewhat correct from infinity to about 5 feet, and then incorrect increase when focus closer.
Scale in purple is what real distance scale should be, according to my curve. You can notice that distance less than 5 feet(1.5m), the curves significantly differ, and when the rail extends to the end, it actually focus at about 3.6 feet, not 3 feet.
I should re-mark the distance scale on Byron