Digital BW, The Print

Hi Jerry,

> But Austin, If you had a 16x24 print from a velvia slide and the same
> size from a 20 megapixel camera, (with a top of the line Leitz, Zeiss,
> Canon, or Nikkor Lens), could anyone on the planet see any difference,
> anywhere in the print?

Yes.  It would be image dependant, and I agree that some images differences
may not be able to be seen.  And it depends on if the 20M were real pixels,
or interpolated pixels.  Real pixels would make it a LOT tougher.

> I doubt it very much. Of course if you're
> speaking of billboard size prints, you'd need the 100 meg. An 8x10 print
> from a Canon D30 absolutely equals a velvia slide. Ther is no question
> about it.

No question that it doesn't.  It depends on what you are considering
"equals".

> I've done this comparison many times.

Me too.

> You just can't see any
> difference that's worth talking about.

I can.

> Your figures may be correct, but
> what difference could it possibly make?

The image detail isn't there.

Austin

> Jerry
>
>
> Austin Franklin wrote:
> >
> > > Rather than comparing grain size to resolution, I think an interesting
> > > comparison would be between the film's resolving power and the digital
> > > resolution.  The data sheet for Fuji Velvia, for instance, says it can
> > > resolve 80 lines/mm at a chart contrast of 1.6:1.  The
> > > measurement for this
> > > is described in ISO 6328:2000.  Does anyone have a copy of
> this?  What I
> > > don't know is if lines/mm means lp/mm.
> >
> > Hi Thomas,
> >
> > lp/mm means line PAIRS per mm.  One black line, next to one
> white line.  If
> > you have two lines of same color next to each other, then you can't see
> > them.  Reason for solid black next to solid white is because it's %100
> > contrast.
> >
> > Resolution of digital imaging systems is hard to
> measure...since they have a
> > regular structure for their arrays.  The worst case is
> diagonally...which is
> > typically about 1.4x worse than on axis...and most digital
> imaging systems
> > list only the BEST they can do, not the worst!
> >
> > > If you assume it means exactly what it says, "lines/mm," then that
> > > translates to 4064 pixels per inch which would mean an image of
> > > 3840 x 5760
> > > (or 22.1 megapixels) is equivalent.  This is closer to the number
> > > thrown out
> > > by Gordon Brown.
> >
> > 80 line pair/mm is actually 160 lines/mmm, which is what you
> used to do your
> > arithmetic with apparently...since 160 x 24mm = 3840.
> >
> > The big issue to remember when comparing digital imaging
> sensors to film is
> > that digital imaging sensors are regular patterns, and film is
> not.  This is
> > very important when trying to compare resolutions.  Film has a LOT more
> > information than just comparing squared segments (as you are doing when
> > calculating digital equivalent based on lp/mm)...remember the
> diagonal issue
> > I mentioned above.
> >
> > You are also confused by pixels vs sensors.  Digital imaging sensors use
> > FOUR sensor cells to make ONE color pixel...so if you want to
> get the same
> > amount of color information, you need four times the amount of
> sensors!  So,
> > 4 x 22.1 is reasonably close to my claim of 100M pixels.
> >
> > There is also another issue...called sampling.  In the digital
> world, you
> > need to sample at slightly more than 2x the smallest thing you want to
> > RELIABLY detect.  So, in order to RELIABLY detect 160lines/mm
> (only on axis,
> > off axis is 1.4x), you need to sample at 320 lines/mm...in both
> axes (X and
> > Y), therefore giving you 4x your initial estimation of 22.1 M
> pixels, and
> > this doesn't take into account the Bayer pattern (four sensor
> cells for one
> > color pixels worth of information).  Again, showing that more
> like 100M is
> > in reality what is needed to equivalent top 35mm film.
> >
> > So, even the 80lp/mm shown for Velvia, clearly shows that 22.1M
> sensors is
> > clearly not enough to give a reliable 80 lp/mm with digital.
> Others will
> > argue that anything over 40 lp/mm is wasted...and that very
> much depends on
> > what your shooting techniques are.
> >
> > If you want any of this explained any further, I'd be more than
> happy to.
> >
> > Regards,
> >
> > Austin
> >
> >
> > Please visit the Group Homepage to check the Files, Bookmarks,
> Polls and other resources as they are often being updated. The page is at:
> >
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> >
> > Please follow these basic guidelines:
> > - Include your full name with your message.
> > - Include the address of your website, if you have one.
> > - As threads develop, trim off excess portions of earlier
> messages to keep them short.
> > - As the topic of a thread changes remember to change the
> subject header.
> > - Good manners are required at all time. No personal attacks or
> "flames."
> > - Complete your Yahoo profile.
> > - Before posting a question, search the message archives and
> the various resources on the homepage.