Taxacom: digital camera question

Wed Aug 14 14:05:52 CDT 2024

Hi John,

I am not necessarily up with all the research on the subject, but from my
microscopy lab experience in days gone by, taking images with a 35mm camera
is basically equivalent to somewhere around 12 MP digital images. This is
borne out by e.g.
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.reddit.com%2Fr%2FAnalogCommunity%2Fcomments%2Fl79tkt%2Fwhats_the_effective_megapixel_resolution_of_35mm%2F&data=05%7C02%7Ctaxacom%40lists.ku.edu%7C8bed851b409843711d0708dcbc942803%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638592591721598235%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=LWzSPn7hvjKGK%2F7PG4OoLj9d0UmcX18gO780U8SwyYk%3D&reserved=0
where one respondent says: "Depends on a lot of factors including film
speed, film quality, developer/development technique (if B&W), scan
method.  Generally rule of thumb is that a high-quality [35mm] film stock
is capable of about 8-15 MP in perfect conditions."

Now this may not be achievable in practice using a [comparatively cheaper]
dissecting microscope where the optics of the microscope may not be the
ultimate in quality (you get what you pay for, to a degree), also critical
focus may only be achievable on a particular focal plane. So maybe you
could revise this down a bit and say that 5-8 MP might be acceptable in
this instance.

This would give you the equivalent of a fairly sharp 35mm image (e.g. ISO
50 slide film, higher ISO would of course be less sharp) which should be
adequate for most purposes, e.g. a 5x7 inch print at 300 dpi requires 3.15
MP, same at 600 dpi (sharper) requires 12.6 MP (calculation via
https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.scantips.com%2Fcalc.html&data=05%7C02%7Ctaxacom%40lists.ku.edu%7C8bed851b409843711d0708dcbc942803%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638592591721598235%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=Bw61QEDQzE0Xd%2BXxTa2KtdLNomttfiJJjSyC%2BK7vn6M%3D&reserved=0) so somewhere between these 2 is
probably best (sharper is of course better, plus it is always good to have
a little resolution in hand).

These presume that the object you want to reproduce fills the frame of the
sensor. There might be an argument (especially with dissecting microscopes)
for taking the image at a lower magnification (for greater depth of field)
and then enlarging (cropping) just part of the frame to give you the
desired result. However for every 2x decrease in magnification / cropping,
you will need 4x the megapixels to get back to your starting point (same
image size on reproduction).

Hope this helps, it is indeed an interesting topic.

Regards - Tony

Tony Rees, New South Wales, Australia
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On Thu, 15 Aug 2024 at 04:31, John Grehan via Taxacom <taxacom at lists.ku.edu>
wrote:

> I've now had some off list feedback that is addressing the resolution
> issues.
>
> On Wed, Aug 14, 2024 at 10:46 AM John Grehan via Taxacom <
> taxacom at lists.ku.edu> wrote:
>
> > Hope someone on Taxacome has microscope camera expertise that can help me
> > with a question concerning digital camera capability meeting publication
> > needs. I am looking at buying a 'cheap' (less than $1,000 US) dissecting
> > microscope and digital camera through Amscope. They have cameras ranging
> > from 1 to 20 megapixels, but I have no idea how that relates to dpi where
> > publications usually require at least 300 dpi. Can anyone clue me in on
> how
> > to know what megapixel size will likely work to give me a sharp enough
> > image for publication? Currently looking at a 5 megapixel camera which
> > brings the setup well within my limits whereas 10 megapixel goes just
> over.
> > Any enlightenment much appreciated. I am a total moron when it comes to
> > digital camera tech.
> >
> > Thanks.
> >
> > John Grehan
> >
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