And as Reddesert pointed out, even if the theoretical DOF is sufficient for the purpose, still it must be at all possible to achieve it by correct focusing.
Chan, that was my late friend and neighbor Charlie Barringer's lens. It was a joke. f/0.33 is impossible in air. The largest maximum aperture possible in air is f/0.50, as was mentioned earlier in this discussion.
If you want faster than f/0.50, you'll need an immersion objective as used in high magnification microscopes.
Your thread title says it all. A 50mm lens with a 100mm aperture provides a paraxial f/# of 0.5, but the working f/# is significantly slower due to cos^4 law roll-off even on-axis, where f/# is usually specified. At f/0.5 the on-axis marginal rays intercept the image plane at 45 degrees, at which angle relative illumination is down 25% for the marginal rays due to cos^4 law. Quick and dirty estimation tells me that, on-axis, the effective speed is thus actually around f/0.9-f/1.0, but with exponentially worse image quality compared to an actual f/0.9 lens due to aberration dependency on f/#. The same rough calculation says Kubrick’s f/0.7 lens was effectively f/0.85 or so (marginal ray illumination is down to about 47% on-axis)
Off-axis it’s even worse, as at some point the ray angles exceed Brewster’s angle (about 54 degrees for digital camera cover plates, 56.5 degrees for gelatin) and simply reflect off the imaging media, where they then bounce around inside the camera and then contribute to veiling glare and loss of contrast. Effective f/# off-axis would drop to f/4 or less even without vignetting.
An *effective* f/0.5 cannot be achieved, as Brewster angle and cos^4 limits effective f/# to 0.7 or so..it’s an asymptotic approach iirc.
So there you go. Note this limit has nothing to do with technology to fabricate / assemble, practicality of using a lens, nor even image quality. Technology and practically do not limit design work. Laws of physics, however, cannot be broken and create a true limit.
Once you can follow what I wrote, you will no longer have to say you don’t understand why they don’t make a 50mm f/0.5 lens.
-Jason
miha, the medium's refractive index limits the maximum aperture possible. That's why immersion objectives, with oil between the lens' front surface and the subject, can have apertures greater than f/0.5 and why lenses with air between lens and subject can't.I dont think immersion oil (with 100x microscope objectives or similar) has anything to do with the lens f-stop.
So there's really no reason to bother trying to make a lens with an aperture that large. At some point making the aperture wider begins to decrease the brightness and contrast of the image it produces and until it becomes less effective than making a similar lens with a smaller aperture.
I understand that oil has a similar refractive index to the glass lens it touches however this has to with NA (numerical aperture), not f-stop. NA is an indicator of the resolution.miha, the medium's refractive index limits the maximum aperture possible. That's why immersion objectives, with oil between the lens' front surface and the subject, can have apertures greater than f/0.5 and why lenses with air between lens and subject can't.
No kidding... these guys are just too damned smart!If memory still serves me, the Canon 0.9 lens did not have a very good reputation and was not a market success because pics not that good and lens just too large to be practical. I haven’t seen one in person since about 1970. High prices most likely due to collectors’ interest rather than photographers’.
However, I found this thread fascinating. Kudos to all contributors!
miha, numerical aperture = 1/(2*f/number)I understand that oil has a similar refractive index to the glass lens it touches however this has to with NA (numerical aperture), not f-stop. NA is an indicator of the resolution.
I see. Thanks for the explanation Dan.miha, numerical aperture = 1/(2*f/number)
what were you hoping to shoot with it, portraits? still lives? landscapes ? there are ways of achieving selective focus and bokeh&c without a super fast lens like that, that don't cost 12grand+...
have fun !
John
This would be the type of lens which would be hand assembled on demand and sold primarily to Sheikhs and other billionaires.
With the widespread availability of ultra high ISO sensors on digital cameras (I know this is an analog thread), I don't think there would be much of a market for this lens.
The field of view of a 35mm camera with a 50mm lens at 5 meters (magnification = 1/100) is 2.4 x 3.6 meters, which is a bit large for a full length portrait IMO. One might want to use a fast 100mm and step back a little. Or step back a little more: Nikon actually makes a 200mm f/2 lens, B&H price US$5700
....
If people want to engage in speculation about making and using a 100mm f/1 lens, that's great. It would be more challenging than the 200mm f/2 lens so that gives a starting point for what it would take and cost.
Thanks, very interesting.@jjphoto check back through the charts here.
https://www.photrio.com/forum/threads/charts-of-depth-of-field-vs-focal-length-scaling-f.169727/
I think your estimate is pretty close, and you might find the info useful.
cheers,
Jason
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