Taxacom: digital camera question

Thu Aug 15 21:25:51 CDT 2024

Thanks Vlad. All very helpful to my understanding. This and other responses
help lend me some confidence in my final decision.

Cheers, John

On Thu, Aug 15, 2024 at 7:14 PM Vladimir Blagoderov <vblago at gmail.com>
wrote:

> DPI, PPI, magnification are terms that have nothing to do with the quality
> of digital image. Resolution of your microscope (the smallest object you
> can see) is determined by the numerical aperture of your objective and
> nothing else (well, theoretically). The virtual image created by your
> objective will be projected onto a sensor. For each virtual dot
> (minimum resolved object) you must have at least 1.7 pixels in each
> direction for it to be shown as separate on the digital image. There is a
> little bit of physics and math behind it, but the rule of thumb is that the
> lower your objective's numerical aperture, the more pixels you must have on
> your sensor. For example, for a stereomicroscope with 1x objective (0.1 NA)
> you would need to have 20-30Mpx sensor, providing you are using a correct
> projection adapter; with a compound microscope and 63x lens (0.9 NA) there
> is no reason to use anything higher than 2 Mpx
>
> Cheers,
>
> Vlad
>
> On Thu, 15 Aug 2024 at 15:36, John Grehan via Taxacom <
> taxacom at lists.ku.edu> wrote:
>
>> Thanks Tony for that further feedback with respect to slide transparency.
>> Gives me a good comparative context. I also had one respondent using an
>> inexpensive Olympus TG-4 and camera with stacking capability (and sent me
>> a
>> very nice example image). I had not thought about the latter capability
>> being within my price range, but I will make further inquiries.
>>
>> Cheers, John
>>
>> On Thu, Aug 15, 2024 at 12:06 AM Tony Rees <tonyrees49 at gmail.com> wrote:
>>
>> > Hi John,
>> >
>> > Of course it depends on how big you would like to be able to print your
>> > results - e.g. at 300 DPI, a 1 MP image (approx.) would still print up
>> to
>> > about 4 x 3 inches, a 4 MP image up to about  8 x 6 inches, and a 8 MP
>> > image up to about 12 x 9 inches before quality falls off... For many
>> > journal plates, they would be a composite of smaller images than (say)
>> 10 x
>> > 8 inches, so small files would still get you there. On the other hand if
>> > you want something to go on the cover of "Nature" at large size, or
>> just to
>> > create an archive of high quality images, large is definitely better!
>> >
>> > I was intrigued enough by this topic to look further into the old
>> > chestnut of "film vs digital" in which, as alluded to above, I believed
>> > that up to around 12 MP, 35mm film beat digital, and above that, the
>> other
>> > way around (unless you go up to medium format etc.). I did a little
>> test to
>> > see at what point quality loss became visible on a scanned - actually
>> > digitised with a micro 4/3 format, 20 MP resolution Olympus mirrorless
>> SLR
>> > - 30 year-old slide, taken probably at 100 ISO in good light outdoors -
>> > copy put up at
>> >
>> https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcommons.wikimedia.org%2Fwiki%2FFile%3AMaritime_Museum_%252B_James_Craig_1990.jpg&data=05%7C02%7Ctaxacom%40lists.ku.edu%7Ca33cc867a11e44f1b93408dcbd9ad528%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638593720854850796%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C60000%7C%7C%7C&sdata=dzFF%2FctXl6rSU5wQHVpvsrXG7rydv1RSLynJASIMAFE%3D&reserved=0
>> > , So, I digitised this at 20 MP including some of the slide mount; after
>> > cropping the latter off, I was left with 4,908 × 3,234 pixels (15.9
>> MP). I
>> > then down sampled this to 2 smaller sizes and enlarged a small portion
>> of
>> > each image to see when quality loss would kick in. The answer seems to
>> be
>> > that 8 MP is a little visibly worse than 16 MP, and 4 MP definitely
>> worse,
>> > at least when "pixel peeping", see detailed enlargement comparison at
>> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpostimg.cc%2F2V6Rxtn9&data=05%7C02%7Ctaxacom%40lists.ku.edu%7Ca33cc867a11e44f1b93408dcbd9ad528%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638593720854850796%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C60000%7C%7C%7C&sdata=2nml4Kc815VJQjf35xm9vWpPnLOdY2LuWu%2FP9dJikBA%3D&reserved=0 . So this tells me that maybe 16 MP of
>> > digital may well be needed to equate to a good slide (transparency), for
>> > those of us ancient enough to use this as a yardstick; however that may
>> of
>> > course not be necessary unless you wish to print to very large sizes
>> (would
>> > equate to 16 x 12 inches in this example).
>> >
>> > Apologies if the above is too much of a diversion for some, however in
>> the
>> > overall context of "how much resolution is enough" for digital images I
>> > thought it might have some value...
>> >
>> > Regards to all - Tony
>> >
>> > Tony Rees, New South Wales, Australia
>> > https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fabout.me%2FTonyRees&data=05%7C02%7Ctaxacom%40lists.ku.edu%7Ca33cc867a11e44f1b93408dcbd9ad528%7C3c176536afe643f5b96636feabbe3c1a%7C0%7C0%7C638593720854850796%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C60000%7C%7C%7C&sdata=ydTLlQ3ORtrLOo6WO%2ByaGYgrQJotMuylOvvq1Yg2X%2Bs%3D&reserved=0
>> >
>> >
>> > On Thu, 15 Aug 2024 at 11:34, John Grehan via Taxacom <
>> > taxacom at lists.ku.edu> wrote:
>> >
>> >> Thanks Tony and Paulo, as well as an off-line respondent. It looks
>> like I
>> >> will be able to afford up to 18 megapixels. As for the microscope -
>> yeah,
>> >> you get what you pay for. But there is no way I can afford what I see
>> in
>> >> university or museum facilities. But right now I have a microscope
>> that is
>> >> over 50 years old (Kyowa - Japan) and used a small hand held digital
>> >> camera
>> >> which sometimes produced some barely adequate images. So at least I
>> will
>> >> now be better off to some degree. Through the kindness of a couple of
>> >> university and museum colleagues I have been able to get stacked images
>> >> for
>> >> some important dissections.
>> >>
>> >> Cheers, John
>> >>
>> >> On Wed, Aug 14, 2024 at 6:17 PM Paulo Buckup <buckup at acd.ufrj.br>
>> wrote:
>> >>
>> >> > Hi John,
>> >> >         To achieve 300 dpi, each square inch in the final page
>> requires
>> >> > 90,000 pixels. So, a full letter size page (or equivalent in PDF)
>> >> requires
>> >> > over 8 megapixels. Allowing for some loss caused by cropping blank
>> space
>> >> > around your specimen, you need at least a 10 megapixel camera for a
>> full
>> >> > page image.
>> >> >         Keep in mind that if you do any resizing or rotation of the
>> >> final
>> >> > image, the relationship between the pixels in the original camera
>> sensor
>> >> > and
>> >> > the final image is lost, and the quality is severely reduced. So, if
>> >> you do
>> >> > rotating or resizing in photoshop you will need a 40 megapixel
>> camera to
>> >> > avoid individual pixel blurring.
>> >> >         In my experience the "cheap" microscope cameras do not meet
>> >> > traditional publication requirements (but will be accepted for
>> >> publication
>> >> > in open access journals by careless editors, mostly because PDFs are
>> >> only
>> >> > evaluated using monitors that have a resolution way below the 300 dpi
>> >> > standard).
>> >> >
>> >> > Cheers,
>> >> >
>> >> > Paulo Buckup
>> >> > Museu Nacional, UFRJ
>> >> > Brazil
>> >> > -----Mensagem original-----
>> >> > De: Taxacom [mailto:taxacom-bounces at lists.ku.edu] Em nome de John
>> >> Grehan
>> >> > via
>> >> > Taxacom
>> >> > Enviada em: quarta-feira, 14 de agosto de 2024 11:45
>> >> > Para: taxacom <taxacom at mailman.nhm.ku.edu>
>> >> > Assunto: Taxacom: digital camera question
>> >> >
>> >> > 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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>> >>
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