So hoping I can get some advice on choosing a suitable lens for my first scanner build project.
I already have the following :
Camera - Blackmagic 4k. Micro Four Thirds size sensor measuring (18.96mm x 10mm). Native resolution of (4096 x 2160) (DCI 4K) and provides 13 stops of dynamic range. Can used either as frame by frame or record continuous video.
Projector - Elmo K-100SM dual format projector. All electronics and lens removed. Belts replaced, gears cleaned and regreased.
Motion - NEMA 17 stepper motor, Bigtreetech PICO controller, under PC control
LED - SunlikeKorea COB LED SAW0661A CRI 97 7W. MEAN WELL LDH LED Driver. Lee 216 Full White Diffusion. Heatsink, fan etc
Camera trigger - Optocoupler
Post Processing - Davinci Resolve Studio
Without the lens fitted in the projector, there is approx 80mm from the gate to the front of the projector where a lens with a diameter of 75mm could fit. If the lens was to be closer than that then the diameter would have to be less than 40mm.
I have looked at the following lenses but to be honest I am going round in circles and am not an optics expert so dont really know what lens will work best for this application and whether some are overkill as they seem to be very expensive options:
Mitakon 85mm f/2.8 1-5x - 100mm+ working distance. But like hens teath to try to find one with either a micro four thirds or cannon ef mount. Estimated used price £350-400
Rodenstock Apo-Rodagon-D 2x 75mm - Excellent quality, but quite a considerable kit of parts needed to make it work. Estimated used price for bellows, tubes, attachments and lens £650 – £750
ultraVU-EL Zoom System - excellent quality, but soooo expensive by the time all the necessary accessories are included £950–£1,100
Olympus OM Zuiko 80mm f/4 Auto-Macro - older high quality lens designed for medical/scientific scanning, needs bellows/tubes, used £150 – £250
OM-System 90mm f/3.5 Macro/OM MC-20 (2x Teleconverter) - simple system, great quality but very expensive approx £1,500
I am thinking about going with the Olympus (#4) as that seems by far the best bang for your buck. After that it would be the rodenstock (assuming i could find one) as that seems to give the best quality (APO) but is a significant step up in price.
If anyone can help with advice about these lenses, alternatives, or even potentially best sources to purchase these.
Your sensor is 18.96 x 10mm
Super8 frame 5.79 x 4.01mm
The magnification ratio is 2.49
Like many users on this forum, I would simply recommend a 50mm Componon lens with an extension tube.
In your case, the optical calculations suggest an extension tube of approximately 175mm.
The distance from the center of the lens to the frame would be approximately 70mm, perhaps a little too short as the lens diameter is 46mm.
The Rodagon 75mm would be quite similar, but the tube would need to be longer 260mm !
The distance to the projector will also be greater
I used this lens with a PI Camera HQ with a 75mm tube and more recently with a Sony EOS 90D APS-C sensor with a 230mm tube !
There are many posts about building the extension tube and it’s not as expensive as you think.
Here’s a photo of my mount, from left to right:
CANOn to M42 adapter
M42 tubes of varying lengths, approximately 230mm in total
A helical tube for fine-tuning the length and therefore the magnification
An adapter ring for the Componon
The Componon lens
Here the lens is mounted in reverse, but in reality it doesn’t seem very important.
All mounted on an XYZ sliding table. The perfect rigidity of the mount is very important.
I wouldn’t be able to advise you on the characteristics of a macro lens.
Many thanks for the advice. The 50mm Componon lens is an excellent choice. My only problem with that lens is (I think) the working distance, which would be approx 6cm at 4x magnification. To clear the casing of the projector I need close to 8cm working distance. So for the 4x magnification I think i need to be looking at 65mm+ lenses.
I think your magnification is more like 2.5x for Super 8, but even then the working distance is still around 7cm, so it’s too close unless you can move the lens, which has a 46mm diameter, closer. You won’t have this problem with the Rodagon.
Yeah for Super 8 its 2.5x and for standard 8mm its about 4x magnification which makes the working distance problem worse. Thanks for the advice, I think your right about the Rodagon
I think your magnification for regular 8mm is more like 3x. The problem is that with a 75mm focal length lens and a regular 8mm film, the extension tube is really long, almost 300mm! Can’t you get the 50mm Componon closer ? Check carefully with your projector, it’s only 46mm in diameter.
Another possibility, is to reverse the lighting and the camera; that’s what I did, but it’s not but not always possible considering projector’s and camera’s sizes
