Medium format versus digital sharpness

How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch transparency?

Robert

"Robert Montgomery" wrote:
How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

The short answer is that there are no affordable digital systems that
compete with 6x7 and 4x5.

Your mileage will vary, but my experience is that for practical purposes,
12.7MP (the Canon 5D) acts very much like 645. But 6x7 scanned on a Nikon
8000 is noticeably better than the 5D.

So the new 21MP Canon 1DsIII should give 6x7 a run for its money. (Although
the only Canon wide angle lens up to that is probably the new 14/2.8 II L.
And maybe the new 16-35/2.8 when stopped way down. Maybe.)

I'd guess the 39MP digital backs would be encroaching on 4x5 territory.

David J. Littleboy
Tokyo, Japan

Robert Montgomery wrote:

How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

6x7 cm: about 112 MP
4x5": about 352 MP

Please don't believe reports that suggest that 21 MP even comes close to 6x7
quality.

Q.G. de Bakker wrote:
Robert Montgomery wrote:

How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

6x7 cm: about 112 MP
4x5": about 352 MP

Please don't believe reports that suggest that 21 MP even comes close to 6x7
quality.

Doesn't it really come down to print size? :-)

Dana

Recently, Dana Myers posted:

Q.G. de Bakker wrote:
Robert Montgomery wrote:

How many megapixels would a digital camera image file need to equal
the sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

6x7 cm: about 112 MP
4x5": about 352 MP

Please don't believe reports that suggest that 21 MP even comes
close to 6x7 quality.

Doesn't it really come down to print size? :-)

Some people think so, others (including me) don't think that's the whole
picture. ;-)

Compare a 4x5" contact print with a 4x5" enlargement from whatever source
you want, and see if they look the same. To me, they do not. The same can
be said for other format comparisons, and the larger the print, the more
obvious the differences.

Neil

Dana Myers wrote:

Doesn't it really come down to print size? :-)

Not at all.
If about print sizes at all, it is about (not comes down to) the maximum
print size you can get out of each.

"Robert Montgomery" wrote in message
news:NZgNi.145964$bO6.50583@edtnps89...
How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

Robert

There are a Lot of variables involved: the lens used to make the original
image, the method used to make the print (lens or printer) and the type of
film you are using for comparison.

You could make the assumption that to record equivalent detail, the digital
imager would need to have the same number of pixels as the film has grains.
A high speed film has larger grains and fewer of them per area, a fine grain
film has smaller grains and more of them.

A source that I trust (but no longer remember who!) claims that 36Mpixels
equals average consumer 35mm film. A 35mm negative is 24x36mm, so if my math
is right (!), a 6x7 neg would be equal to 175Mpixels.

But you asked for file size-- that brings in more variables if that is
really what you want. Some file types compress the image so that it fits in
a smaller size. For example, an outdoor picture may include an area of sky
of a certain solid color. The file storage won't store individual pixels,
but rather an indication that a certain area is to be a certain solid color.
A photograph of a white sand beach (very little detail) may make a smaller
size file than a close-up of an elderly face (wrinkles, hair, etc.).

On Oct 4, 10:05 pm, Robert Montgomery
wrote:
How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch transparency?

Robert


I put up a page that discusses this for 6x7 along with a sample 6x7
slide
scanned at 4000 DPI. The link is http://chasfs.com/mega.py

The sharpness is affected by the lens, the film, the scanner and any
post
processing. The sample referred to above is about 90 megapixels, and
is
unsharpened. You can play around with it in Photoshop, but may not use
it for commercial purposes. You might try downrezzing it by various
amounts and then uprezzing it to see if you can tell when the amount
of detail is noticeably affected.

Peace,
-chasfs

Ken Hart wrote:

"Robert Montgomery" wrote in message
news:NZgNi.145964$bO6.50583@edtnps89...
How many megapixels would a digital camera image file [..]

[...]

But you asked for file size-- [...]

No, he didn't.
He asked about how many megapixels there would need to be in that file.

Why keep people confusing matters by bringing in megabytes?
The number of those does not tell us a single thing.

"Scott W" wrote in message
...
Q.G. de Bakker wrote:
Robert Montgomery wrote:

How many megapixels would a digital camera image file need to equal the
sharpness of a six-by-seven centimeter or a four-by-five-inch
transparency?

6x7 cm: about 112 MP
4x5": about 352 MP

Please don't believe reports that suggest that 21 MP even comes close to
6x7 quality.



Hmmm, 112MP from 6x7, that is pretty impressive and far past anything I
have seen, you go a scan that shows that?

Scott

I'm not sure how Q.G. came up with the 112 MP figure but it's not
implausible.
You figure desktop film scanners such as those from Nikon and Minolta can do
4000 DPI.
Taking a 6x7CM transparancy and converting to inches 2 1/4x4000=9000

2 3/4x4000=11000

9000x11000=99MP
Now when you get into drum scan terrority the resolutions get much higher.