Calculating monitor magnification- no intermediate lens

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cwilli62
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Joined: Sun Jun 26, 2022 8:52 pm

Calculating monitor magnification- no intermediate lens

#1 Post by cwilli62 » Thu Dec 29, 2022 1:31 am

I tried to calculate the total magnification that I'm viewing on my computer screen with a camera as described in this link:
https://www.microscopeworld.com/p-3375- ... ation.aspx

However, I don't think that my calculation was correct.

Objective magnification: 40x
Computer monitor: 711.2mm (28")
Sensor size: 21.6mm on the diagonal (MFT)
Adapters: MFT to c-mount AND c-mount camera adapter for Nikon microscope with ISO 38mm pot
(neither adapter has an intermediate [reduction] lens)

So the equation, according to the link, would be as follows:

Objective Magnification x C-Mount Adapter Magnification = Optical Magnification
40x1= 40

Screen Size / Sensor Size = Digital Magnification
711.2/21.6= 32.93

Optical Magnification x Digital Magnification = Total Magnification
40x32.93= 1,317.2

This doesn't seem to be correct to me. What am I missing here?

Scarodactyl
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Joined: Sat Mar 03, 2018 9:09 pm

Re: Calculating monitor magnification- no intermediate lens

#2 Post by Scarodactyl » Thu Dec 29, 2022 2:13 am

I think your calculation is correct, but as you've noticed the number seems ludicrous. That's because calculating magnification on a monitor is really not very meaningful. As a concept it is pushed by vendors who want to quote magnification numbers that are the next best thing to fraudulent. It is not really used in any other context than marketing.
Optical magnification is a good baseline bit of information but field of view (how wide the captured field in your image is) is the metric that ultimately matters. After all a 10x objective used directly on a 1" c mount camera, a m4/3 camera and an aps-c camera each give very different images, and that's before you get into different magnification factors on your adapters and dofferent field numbers on objectives. If you know the field of view you can do an apples-to-apples comparison across images no matter what setup was used.

cwilli62
Posts: 27
Joined: Sun Jun 26, 2022 8:52 pm

Re: Calculating monitor magnification- no intermediate lens

#3 Post by cwilli62 » Thu Dec 29, 2022 2:55 am

Scarodactyl wrote:
Thu Dec 29, 2022 2:13 am
That's because calculating magnification on a monitor is really not very meaningful. As a concept it is pushed by vendors who want to quote magnification numbers that are the next best thing to fraudulent. It is not really used in any other context than marketing.
Nice. This is helpful information. I just assumed that the magnification number on the monitor would be useful in some way... especially when compared to total magnification of eyepieces and lens together. Good to know that it isn't something to pay attention to. Cheers!

MichaelG.
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Location: North Wales

Re: Calculating monitor magnification- no intermediate lens

#4 Post by MichaelG. » Thu Dec 29, 2022 8:38 am

.

If you want to ‘get your head around’ this … it’s easier to think in terms of angles of view instead of linear or area magnifications.

[Hint] … we don’t usually print a photo at 20” x 16” and then view it from a foot away.

MichaelG.
.

P.S. __ This, from Leica, is probably the most rational explanation [justification?] of the enormous results of your calculation: https://www.leica-microsystems.com/scie ... ally-mean/
… and here is something more concise, from Zeiss: https://www.microbehunter.com/microscop ... 25&t=14884
Last edited by MichaelG. on Thu Dec 29, 2022 9:09 am, edited 2 times in total.
Too many 'projects'

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WWWW
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Location: The Netherlands

Re: Calculating monitor magnification- no intermediate lens

#5 Post by WWWW » Thu Dec 29, 2022 8:45 am

Why not using a object-micrometer ?
The distance is known and you can measure the distance on the monitor.

cwilli62
Posts: 27
Joined: Sun Jun 26, 2022 8:52 pm

Re: Calculating monitor magnification- no intermediate lens

#6 Post by cwilli62 » Fri Dec 30, 2022 1:46 am

MichaelG. wrote:
Thu Dec 29, 2022 8:38 am
.

If you want to ‘get your head around’ this … it’s easier to think in terms of angles of view instead of linear or area magnifications.

[Hint] … we don’t usually print a photo at 20” x 16” and then view it from a foot away.

MichaelG.
.

P.S. __ This, from Leica, is probably the most rational explanation [justification?] of the enormous results of your calculation: https://www.leica-microsystems.com/scie ... ally-mean/
… and here is something more concise, from Zeiss: https://www.microbehunter.com/microscop ... 25&t=14884
Awesome! Those articles definitely helped!!

cwilli62
Posts: 27
Joined: Sun Jun 26, 2022 8:52 pm

Re: Calculating monitor magnification- no intermediate lens

#7 Post by cwilli62 » Fri Dec 30, 2022 1:48 am

WWWW wrote:
Thu Dec 29, 2022 8:45 am
Why not using a object-micrometer ?
The distance is known and you can measure the distance on the monitor.
I have a stage micrometer. I know how to get the FOV. After reading the article in the link of the original post, I was just wondering about total magnification on a computer screen and what it means.

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