# Canon 5D vs. Medium Format (Film)

Discussion in 'Digital Photography' started by Progressiveabsolution, Sep 25, 2006.

1. ### RichAGuest

You'd be correct, but only for the same lens. As the f-number of a
specific lens increases, it's aperture is decreasing. However, a
100mm lens at f10 will resolve detail twice as fine as a 50mm lens
at f5 because f-ratio has nothing to do with the resolution of detail,
aperture determines that.
This is easily proven provided you can take each lens to it's
diffraction limit and pixel size of the camera will support detail
that small as extended objects.
R = (1.22 * w) * (f / D)

where f is the focal length of the primary mirror(or lens), w is the
wavelength of the light, and D is the diameter of the primary mirror,

Actually, a more precise equation is given by:

R = (1.22 * w) / (n SIN(u))

RichA, Oct 5, 2006

2. ### David J. LittleboyGuest

No. The f number uniquely determines the diffraction limited resolution at
the sensor regardless of focal length. At which point, for the same f
number, the focal length determines the resolution of hte subject.
Hello? The 50/5.0 has exactly the same aperture as the 100/10 and the
angular (or subject) resolution will be exactly the same.

Did you actually have this wrong (which would explain why you object to my
TC arguments) or was it just a goof?

Assuing you meant that a 100/5.0 will resolve twice the detail of a 50/5.0,
no one was ever arguing that it wouldn't. Since TC's reduce the f number
(i.e. don't increase the aperture), you don't get any additional diffraction
limited resolution.

David J. Littleboy
Tokyo, Japan

David J. Littleboy, Oct 5, 2006

3. ### Roger N. Clark (change username to rnclark)Guest

Here is a guy who does great planetary imaging with a 250 mm
aperture at f/42, so 6,000 mm.
http://www.sg-planets.org/mars.html

I've done something like f/115 at 203 mm aperture:
http://www.clarkvision.com/galleries/gallery.astrophoto-1/web/jupiter-8-a.html
so 23,460 mm (this was before digital).

I've also done planetary imaging with the UH 88-inch
on Mauna Kea at f/10, so 88*25.4*10 = 22,350 mm (also with film)

Planetary Patrol imaging done on Mauna Kea used 24-inch
(diameter) Cassegrain telescopes working at f/75, so
24*25.4*75 = 45,720 mm (with film). Those telescopes were
decommissioned in the 1980s if I remember correctly.

I'm not aware of any amateur astronomers working at 200,000mm,
but 50,000 wouldn't surprise me.

Roger

Roger N. Clark (change username to rnclark), Oct 5, 2006
4. ### Roger N. Clark (change username to rnclark)Guest

Yep, I agree. But the fact that people have such negative reactions
is further indication that it is a myth. ;-)

Roger

Roger N. Clark (change username to rnclark), Oct 5, 2006
5. ### RichAGuest

No, resolution, the ability to show detail of a specific size, is
solely determined by the aperture and is proportional. F-ratio has
nothing to do with resolution. I only used the faster f-ratio for the
50mm to illustrate the point that f-ration has no bearing on
resolution. However, because lenses used at prime focus cannot
approach their true resolving ability, proving this with camera lenses
is difficult. It's easy with a telescope.
If that were true, then you'd see diffraction effects the moment you
stopped down a lens by even a small amount because you are saying that
you are operating at the lens's diffraction limit when using a lens in
prime focus (just the lens and camera) mode. The fact you don't see
diffraction degrading the image until you hit around f16 or f22 proves
that no camera lens is operating in prime focus at it's diffraction
limit. To do that, you must interpose a second lens to increase the
overall system focal length.
The only way you'll ever get diffraction limited performance using a
lens on it's own is to have a sensor with pixels so small they could
record detail at the diffraction limit using only the fixed
magnification of the lens at prime focus. They would be very small
pixels. According to Olympus, the standard kit lenses they have are
"good" to 22 megapixels in the 4/3rds format. We will likely never
see that kind of density in a consumer camera.

RichA, Oct 6, 2006
6. ### Verne AraseGuest

You're talking about Apple's MacOS X, right?

Verne Arase, Oct 17, 2006
7. ### ASAARGuest

Hey, Verne, It's Ernest! No, I didn't mean that. KnowWhutImean,
Verne?

ASAAR, Oct 18, 2006
8. ### Kinon O'CannGuest

Of course, there's a huge difference when MS does this, as opposed to Apple.
Apple is trying to gain market share by adding value, MS is trying to steer
standards in their direction to tighten their hold on the OS monopoly.
Remember, MS was ruled to be an abusive monopoly by the courts and gets
treated differently than Apple.

Kinon O'Cann, Oct 19, 2006

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