> On 9/20/96 ,David Fokos thoughtfully and extensively commented on the
> overall benefits and assets of digital imaging. In Feb of this year, I
> went to India with my 7x17 inch Canham Camera to photograph. I literally
> weighed in at 400 pounds including 10 filmholders and 50 pounds of HP 5+.
O.K. I'm impressed! *whew*
> I took this cumbersome camera because I did not want to sacrifice the loss
> of quality that would result in taking a smaller camera and making an
> enlarged internegative. So if I interpret this technical discussion
> correctly, the implication is that I could do the same with a much more
> manageable 4x5 or even a 2 1/4 which would be a living dream , use a lot
> more film, end up with nice large 16x20 inch platinums and suffer no loss
> of quality at all. The excess baggage costs ( $300.00), taxi costs , large
> equipment cases, and advil for backspasm would easily pay for the cost
> of the scans. Moreover, 4x5 film and certainly 2 1/4 film unlike 7x17
> inch film can circumvent x-rays and be hand inspected. It sounds too good
> to be true.It feels like we are defying the laws of gravity and cheating
> nature. Is it true ??
Well, yes and no. The unsharp making (sharpening) feature does, to me
anyway, defy the laws of nature, at least a little bit. You aren't
really getting anymore detail than you had on the film, however, the
print *looks* sharper -- and that's all that counts.
It works by increasing the contrast right along the junction between two
adjacent tones -- kind of like accutance, I guess. In any case, it *does*
work, but there are practical limits. You can't enlarge a 35mm neg up to
16x20 and make it look like a contact print. However, I think you could
take a 4x5 negative and get there, or if not exactly there then darn
close. In fact, I just set myself up with a 4x5 to do just that. It will
be so much lighter and cheaper to use than my 8x10. Just think of the
depth of field! I know, I know. Compared with your 7x17, a 4x5 is a
point-and-shoot.
It all comes down to enlargenment. Can the film resolve something 4.5
times smaller than the eye can see *on your print*? This is obviously more
likely to be true on a platinum print than on a silver gelatin print. If
so, then the results will be the same if you contact print a 16x20 neg or
enlarge a 4x5 neg (image area 3.625" x 4.625"). The difference that you
usually see is the fuzziness which comes along with the optical
enlargement. However, in the case of digital enlargement+sharpening you
can largely defeat this fuzziness, hence the apparent suspension of the
laws of physics.
> If so that is a definite plus for digital imaging.
> Photography in third world countries is extremely difficult and this
> presents a method for doing it with much less grief and bachache. But are
> my assumptions reasonable? Are we talking about a range of $30.00 or
> $50.00 for a final negative paid to the service bureau. Is it reasonable to
> go from say a 4x5 to a 16x20 in terms of cost?
While larger film output does cost more, the increase in cost is often not
huge. What service bureaus charge you for is time. The larger the
negative, the larger your computer file will be. That means it will take
longer for their machines to process the data. And, as they say, time is
money. The company I'm dealing with will make me a 16x20 neg for about $30.
But be sure to call around as the prices vary *a lot* from one place to
the next.
> One other question: What limits do these scanners have in terms of dpi ? .
> Does it cost more to scan it at 2400 dpi than at 1333 dpi. Is 2400 dpi a
> big number in reference to these scanners? What is a reasonable degree of
> enlargement with todays technology . I assume that the greater the
> enlargement, the greater the cost. Is this true?
The Howtek scanner I am using can go up to 4000 dpi. I have a catalog
which has $15K drum scanners that can do 3000 dpi, $10K non-drum scanner
from Polaroid which can accept a 4x5 neg (that's the largest it will take)
and output up to 2000 dpi, and a $5300 flatbed scanner which can take film
as large as 8x10 and output at 1000 dpi.
If you pay a service bureau to scan your negative, you again pay for the
time. The larger the file -- that is, the higher the resolution -- the
more time it will take to scan and the more it will cost. As for pricing,
most service bureaus charge by file size, not by resolution. To get file
size, multiply the dimensions by the resolution. For example, to
calculate the file size resulting from scanning a 4x5 negative at 2000 dpi
you would first take the film area -- in this case, 3.625" x 4.625" -- and
multiply each of the dimensions by the resolution. So, 3.635" x 2000 dots
per inch = 7250 dots. That's how many dots will run in the short
direction of the image. In the long dimension you will have: 4.625" x
2000 dpi = 9250 dots. The total number of dots will be 7250 x 9250 =
67,062,500 dots which is also known as 67 megabytes.
As for the maximum enlargement possible... Well, like all photography
that depends upon what you are willing to accept. If you are willing to
accept some additional image degradtion because you expect the print to
be viewed from a farther distance, then perhaps even more extreme
enlargements are possible. I can't really answer this question for you.
You'll have to decide that through your own experimentation. However, I
will say that no matter what the enlargement, the digital negative
(provided you follow all the proper rules of resolution) can yield an
image superior to an image made by optically enlarging the same size
negative. For myself, I will be content to enlarge 4x5 negs up to
16x20. For now... :)
David Fokos