[filmscanners] Re: film and scanning vs digital photography

["James L. Sims" <jlsims@knology.net>]

I have been trying to follow this thread, with some difficulty -
probably my old age.  But to keep perspective and depth of field equal,
when comparing Full Frame with smaller formats, lens focal length,
circle of confusion, or blur circle, size must be adjusted
proportionately. Control of chromatic aberrations become
proportionately more restrictive.  Then there's Lord Rayleigh's Criteria
regarding Diffraction Limit is just as true today as it was when he
published it.  Therefore, with today's APO lenses, we can achieve very
high quality images, with smaller formats.  BUT, to achieve sharp
images, the minimum acceptable lens aperture size will increase (f:#
will decrease) because of diffraction.  Having said this, I'm very
pleased with my Canon 20D, The two lenses I have are incredibly sharp,
and zoom lenses at that (I did think that no zoom lens could equal a
prime lens but that may be changing) but I try to stay within its
limitations - shoot at the lowest ISO that I can get away with and
control exposure time to stay within a range of f:4 to f:11.

Jim

David J. Littleboy wrote:
> From: "R. Jackson" <jackson.robert.r@comcast.net>
>
> So a birder, for example, will have a two-stop DOF advantage over a
> FF guy right out of the gate just because of his format of choice.
> Add in the faster Zuiko f/2.0 lens at ISO 100 and he can use a higher
> shutter speed at a lower aperture all day long.
> <<<<<<<<<<<<<<<
>
> It don't work that way<g>.
>
> The 5D user shoots at ISO 400 with the same image quality (photon shot
> noise) and same shutter speed and sees the same DOF (and same background
> blurring effects) at f/4.0 as the 4/3 user does at f/2.0.
>
> It is seriously cool how digital cameras with the same pixel count scale
> across formats.
>
> (At ISO 100, the 5D should have a two stop dynamic range advantage, except
> that the A/D converters don't have enough bits.)
>
> Note, of course, that you have to use a larger lens on the 5D to get the
> low-light high-ISO advantage. The 100/2.0 is a bigger lens than the Oly
> 50/2.0 (I'd guess, anyway.)
>
> The bottom line is that if you think a smaller format buys you anything
> other than lighter weight/smaller size/lower price, you've done your math,
> physics, and/or optics wrong.
>
>
> You're right, though, when you get to the end of the day and the
> light starts to fall the extra speed of the lens becomes a crutch
> that attempts to overcome the limits of the sensor. Still, the high-
> end Oly glass tends to be very sharp wide open and you don't have to
> stop them down much at all to hit their sweet spot.
> <<<<<<<<<<<<<<<<<<<<
>
> You are already shooting two stops smaller with the 5D for the same DOF. And
> for portrait work, you don't shoot at f/4.0 with FF, you shoot at f/2.0 and
> wider. For a DOF effect that simply isn't available from the 4/3 format.
> (Although I wish Canon had an 75 or 85/1.4. The f/1.2 is overmuch.)
>
>
>> Note that to actually be equivalent, the 4/3 lens has to provide
>> _twice_ the
>> resolution (twice the lp/mm at any given MTF, or an MTF curve
>> shifted up by
>> a factor of two due to the finer pixel pitch) at f/2.0 than the FF
>> 28-70mm
>> lens does at f/4.0. (Interestingly, MTF performance does scale up with
>> decreasing format sizes, so this point may not be a problem; but
>> the need
>> for twice the resolution at a much wider f stop may be problematic.)
>>
>
> This is the biggest problem with the format, IMO. You're always going
> to be fighting that battle. It's the same thing with shooting 16mm
> instead of 35mm cine stuff. The 16mm gear is lighter, has greater DOF
> for run-and-gun work and is obviously a lot less expensive to work
> with. But the frame is roughly a quarter the size of the 35mm frame,
> so the glass always has to be much better than glass would have to be
> on a comparable 35mm rig and obviously the grain is going to be
> magnified on top of that. A grain pattern that looks subtle and
> wonderful in 35mm may look really bad in 16mm, so you can't even use
> the same standards of judging what stock to use because 5263 is not
> the same at the end of the day as 7263 when you take the format into
> consideration.
> <<<<<<<<<<<<<<
>
> That's the difference with digital: you can get a reasonable 10MP image from
> the 4/3 camera at ISO 100. You really can't get a reasonable film image from
> 1/4 the area of 35mm.
>
>
> So that's the rub when you have to decide on buying glass from
> Olympus now. The 35-100mm f/2 is a really nice lens. Effectively a
> 70-200mm f/2 lens, but it carries a price tag of $2200. Is it equal
> to a Nikon 70-200mm f/2.8 on APS? Or a Canon 70-200mm f/2.8 on a FF
> camera?
> <<<<<<<<<<<<<<<
>
> Again, if you are using a 10MP 4/3 camera, then the comparison is with the
> 70-200/4.0 (IS). Without IS, it's half the price, with about 3/4 the price.
> And those are phenomenally good lenses that you are putting in front of very
> widely spaced pixels. There's no need to stop down with the 70-200/4.0.
>
>
>  Hard to say. More than the MTF numbers of the lens play into
> it, of course. Those Canon FF cameras have a sensor with a diagonal
> nearly as wide as their lens mount where the 4/3 sensor is tiny in
> comparison to the 4/3 mount. That allows a lot of advantageous
> geometry when it comes to lens design and how the light strikes their
> sensor it a big part of the "4/3 advantage" (to quote the nauseating
> Olympus PR machine).
> <<<<<<<<<<<<<<<<<
>
> The "telecentric" bit strikes me as nothing other than lying snake oil.
> (Real telecentric lenses aren't used for pictorial photography, they're for
> machine vision applications, and the ray tracing diagrams on the Oly site
> show optically impossible paths.) As before, it's not even a 30 degree angle
> of incidence with the Canon mount, and there's no difference with longer
> lenses.
>
>
> At the end of the day I think it's about what camera you enjoy using
> as much as almost anything else, unless you have some particular
> application that draws you to one camera over another. I prefer CCD
> sensors and my E-1 and now my D200 both have CCDs.
> <<<<<<<<<<<<<
>
> At the end of the day, one shoots a camera that meets one's needs. If the
> 4/3 meets your needs, there's no reason to move to a larger format (just
> don't try to tell me that it's better; it ain't). Just as 645 meets my needs
> but not the needs of someone making larger landscape prints.
>
>
>  I don't know what
> options will be available to me in the future, though. I'd love to
> see the Foveon chips get it together. I'd take full color information
> over just about any other consideration, but so far I'm unconvinced
> that they've got that format ironed-out.
> <<<<<<<<<<<<<<
>
> Foveon doesn't buy you anything the human eye can actually see. And not
> using a low-pass filter reduces real resolution by it's snap-to-grid effect
> which puts features in the wrong place; it's an artificial sharpening trick
> at best.
>
> David J. Littleboy
> davidjl@gol.com
> Tokyo, Japan
>
>
>
>
>

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