Resolution
is a term
you see used often on the internet and in the photography world. While
the basics of resolution are easy to understand, few have a grasp on
the
true implications of resolution. Bit rate, density range, dynamic
range, and a host of other factors are often incorrectly associated
with resolution. Here we will deal strictly with resolution.
Above are
two images
of the same building captured on two different forms of media. The
image on
the left is a full frame shot from a modern dSLR, Canon 1Ds Mark II.
The image on the right is a
6x7 crop of a larger 4X5 piece of film shot on a hundred year old
view-camera.
Both lenses had similiur sharpness when compared on an iso122333
chart. While comparing two first generation digital images would have
been optimal, the cost of 100+ megapixel cameras currently make that
comparison
un-available for us at this time.
The image
above is from a
cropped portion from the digital camera image. Note the loss of detail
on the hand rails
and around the roof line. The smoother appearance of the image is due
to the fact that digital capture does not suffer from film grain. The
same effect
can be achieved on the scannned image by applying a 5px gaussian blur.
Before
correcting for
a transmission scan, the film scan was obviously exposed differently.
For resolution comparison, this will not drastically effect
any
of
the aspects we are covering. While grain is present, the
overall
appearance of the image is sharper with smoother transiitions.
So how
does a 100
mega-pixel file compare to a 20 mega-pixel file when printed?
It all depends on the size of the final print. Above are crops of
the digital file, showing how the print would look
at different print sizes for the cropped region.
When printed at 8x10, both images exhibit acceptable sharpness. By
20x24
the film image is showing grain, but is still acceptable for most work,
while the digital has become too soft for most applications. At 28x36
if a filter was applied the higher resolution film image would still be
usable. As an interesting aside, a 100+ megapixel camera can be well
over $75,000 while a 6x7 film camera can be purchased for under
$500.
Now that
we have
established that drum scans of film, definitely have much higher
resolution than the current crop of high end (35mm format, 17.2 mp)
digital cameras, exactly how much resolution
can you squeeze out of a piece of film. While no one seems to think
drum scanning film at 8000dpi is worth while, there is ongoing debate
between
2000dpi and 4000dpi.
With Fuji
Provia 100, shot on a Mamiya Pro S,
there is very little difference in appearance between 2000dpi and
4000dpi.
For over double the file size you will be rewarded with a print that
may be slightly sharper. This is not to say there may not be a
difference with something like Velvia 50 or film with finer grain, but
we will save that comparison for
a later time.
In
conclusion we have
shown that at least with the current crop of high end 35mm format
digital cameras, the ability to resolve detail at higher
magnifications does not come near to the resolving power of drum
scanned Provia 100 film. Further, that at least with Provia
100,
there is not much benefit gained by scanning at 4000dpi vs 2000 dpi.
