Not necessarily, Ray. A "normal" lens on an 11 x 14 camera is about 500mm. f/64 on a 500mm gives an aperture of about 8mm. The governing factor in blade diffraction is the size of the hole, not the f number. With an 8mm hole (which is about the focal length of some point-and-shoot lenses) you simply don't get much, if any, diffraction.
Yes, necessarily, Russ. The laws of diffraction cannot be defeated, although I admit there is some interesting research currently going on with regard to artificial materials designed with a negative refractive index using nanotechnology, which may eventually result in camera lenses that are just as sharp at F64 as at F8.
The actual size of the hole is certainly a governing factor in diffraction, as you mention, but it's clearly not
governing factor. Magnification plays a huge role.
For the sake of simplicity, lets compare the full-frame 35mm format with an 8"x12" field camera that has the same aspect ratio as the 35mm format.
The standard lens for 35mm is closer to 45mm than 50mm, so lets compare a 45mm lens at F8 (on 35mm format) with the equivalent standard lens on an 8"x12" large format, which would be 360mm.
The physical size of the aperture on a 45mm lens at F8 is given by a very simple formula that everyone should be able to understand. You simply divide the focal length by the f/stop number. For example, 45/8=5.625. The diameter of the aperture at F8 is 5.625mm.
Let's apply that formula to our standard 360mm lens on the 8x12 format used at F64. 360/64=5.625. What a surprise! The aperture is the same size as that on a standard lens on 35mm at F8. That means that the Airy Disk will be the same size at the exit pupil of both lenses.
However, let's consider what happens to that Airy disk when it reaches the film surface. The 360mm large-format lens magnifies the Airy Disks, just as it magnifies everything else in the scene to fill the larger area of film. It magnifies it 8x more than the 35mm standard lens.
Theoretically, if we were to exclude factors such as film grain, and imagine we had perfect lenses that were truly diffraction limited at the F/stops used, then an 8"x12" format used at F64 would have no resolution advantage over 35mm format using the equivalent standard lens at F8.
However, in practice, because we don't have 35mm lenses that are so good that they are completely diffraction limited at F8, the large format at F64 will have a slight resolution advantage. In other words, the image from the 35mm lens will contain some of the usual lens aberrations in addition to
the effects of diffraction at F8, whereas the Large Format lens at F64 will be much closer to being truly diffraction limited.
Theoretically again, if a lens is completely diffraction limited at a particular F/stop, then doubling that F/stop number will result in a halving of resolution in the projected image
. F16 will produce half the resolution of F8. F32 will produce 1/4th the resolution of F8, and F64 will produce 1/8th the resolution of the lens used at F8.
However, since a large format 8"x12" is 8x the size of 35mm format along each dimension (or 64x the area), the resolution of the projected image from the 360mm lens in terms of line-widths per picture height, should be the same as the image from the 45mm lens at F8. But I emphasise that I'm referring to the projected image, not the recorded image,
just in case you get all hot under the collar.
The resolution of the recorded image in the case of film will also be influenced by the properties of the type of film used, the fineness of the grain and so on. For static subjects where long exposures are possible, the large format will have a clear advantage with less noticeable grain.
It would be interesting to see a comparison of the 35mm format used with a very fine-grain ISO 25 film at F8, and the large 10x12 format used with a grainy ISO 1600 film required for the same shutter speed at F64.
Now, as we should all know, one of the major features of the digital camera is its lack of grain. The large format film camera thus loses one of its main advantages which it had over the smaller film format, when it's compared with a small digital camera.
It may still retain some advantages in respect of resolution and dynamic range. However the resolution advantage of the larger format falls off rapidly if one equalizes DoF by using F64, and the dynamic range advantage is only apparent if the scene being photographed is very contrasty.
What frequently tends to be a problem when comparisons are made between large and small formats, such as Michael's comparison between the Canon G10 P&S and the Phase P45+ MFDB, is the dilemma of equalizing all the variable parameters, such as shutter speed and DoF.
The larger format generally has an advantage in respect of shallowness of DoF, and the smaller format the advantage of a more extensive DoF at any particular F/stop.
If one attempts to equalize a shallow DoF in the comparison, the smaller format may not be able to do the job. The maximum aperture may simply not be wide enough. If one decides to compare images with an extensive DoF, the larger format may well be up to the job, especially if the lens stops down to F64, but the resolution fall-off due to diffraction, and the image degradation due to use of a high ISO to maintain equal shutter speed, just might result in the smaller format producing the better image.
An interesting point that arose from Michael's G10/P45 comparison ,which was not followed up as far as I know, was the DoF issue which became the clue when the A3+ prints from both cameras were examined. One of the prints had a noticeably shallower DoF and that, it would be reasonable to assume, would likely be the print from the P45.
The G10 was used at F3.5 and the P45+ at F11. Both images at A3+ size appeared to have the same resolution in the main area of focus. A quick calculation comparing sensor sizes reveals that the P45 should have been used at F22 to achieved the same DoF as the G10 at F3.5.
I can't help wondering what the outcome of the comparison would have been if F22 had been used with the P45 MFDB, instead of F11. The resolution at F22 would clearly be worse, but would that fall-off in resolution be noticeable on an A3+ size print? Probably not, in which case the two prints would have been indistinguishable. But just maybe, the G10 print might have shown a very slight resolution edge, only discernible by the expert photographers examining the prints, in which case they would have incorrecly assumed that the print with the barely noticeable resolution edge was from the P45.
Well, I hope you've all enjoyed my brief introduction to a few photographic technical issues.