Posted by
Tim Feinstein on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Are-lower-magnification-objectives-brighter-tp7592013p7592018.html
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You have to take the NA into account. I have not looked up the physics, but Christoph Ruediger's heuristic sounds about right.
You have to take coatings and lens elements for correcting chroma, flat field, etc into account as well, as each element & coating will necessitate some light loss. I recall the brightest objective in one scope maker's product line (at the time that I asked) was a 40x 1.3 with modest chroma correction that hit a sweet spot between magnification, NA, and the number of lens elements & coatings.
That makes me wonder whether microscopy has anything like the famous 50mm/1.8 lenses for photography. That length & aperture hit an engineering 'sweet spot' that let you get near-perfect optical quality with a minimum number of all-spherical lens elements. Every manual SLR camera used to come with one because the makers could all produce amazing ones in a compact size and basically for free. If such a thing exists in microscopy I haven't heard about it.
All the best,
T
Timothy Feinstein, Ph.D.
-----Original Message-----
From: Confocal Microscopy List <
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Sent: Monday, March 22, 2021 1:21 PM
To:
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Subject: Re: Are lower magnification objectives brighter?
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Hi Andreas,
I've always understood this in relationship to a constant detector with a given pixel size (like a camera): lower magnification spreads the same signal over a smaller number of pixels, resulting in higher intensity for the pixels that contain the signal. This is more tricky with point-scanning microscopes.
Christophe
On Mon, 22 Mar 2021 at 18:02, Andreas Bruckbauer <
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> Dear all,
> Are lower magnification objectives brighter than higher magnification
> ones when they have the same NA, e.g. a 40x NA 1.4 objective compared
> to 63x NA 1.4? I mean for confocal microscopy.
>
> Confocal.nl stated this is a recent webinar and on their website:
> "A lower magnification allows for a larger field of view and brighter
> images, since light intensity is inversely proportional to the
> magnification
> squared"<a href="https://nam12.safelinks.protection.outlook.com/?url=https%3A%2">https://nam12.safelinks.protection.outlook.com/?url=https%3A%2
> F%2Fwww.confocal.nl%2F%23rcm2&data=04%7C01%7Ctnf8%40PITT.EDU%7Cf2c
> 11405023a4bd8240908d8ed575e19%7C9ef9f489e0a04eeb87cc3a526112fd0d%7C1%7
> C0%7C637520306784421783%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLC
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>
> I would think that this is caused by less light going through the
> smaller back focal aperture when the illumination is held constant?
> Most of the light is clipped as explained in fig 1 of
>
https://nam12.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.
> nature.com%2Farticles%2Fs41596-020-0313-9&data=04%7C01%7Ctnf8%40PI
> TT.EDU%7Cf2c11405023a4bd8240908d8ed575e19%7C9ef9f489e0a04eeb87cc3a5261
> 12fd0d%7C1%7C0%7C637520306784421783%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC
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> ata=NMagM%2FIuo%2BVswcZuCnx%2B5GIO92Mv6m%2BGxoA9AOES%2BoM%3D&reser
> ved=0 So, the microscope manufacturer could adjust the illumination
> beam path and laser powers to best suit the objective?Or are lower
> magnification objectives really brighter?
>
> The field of view will obviously be larger for the 40x objective, but
> I am more interested to understand the claimed benefit in brightness.
>
> best wishes
>
> Andreas
>