Re: [EXT] Are lower magnification objectives brighter?

Posted by Michael Giacomelli-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Are-lower-magnification-objectives-brighter-tp7592013p7592016.html

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Hi Andreas,

If you divide the same amount of light across a more magnified PSF, then
the PSF covers more pixels and so each pixel gets fewer photons.  However,
in this case you would also be more densely sampled, and you could
digitally downsample the image, which would have the effect of putting the
same number photons into fewer pixels.  If dark and read noise are low,
this would effectively give you the same image as you would have gotten
using a lower magnification to begin with.

Mike

On Mon, Mar 22, 2021 at 1:02 PM Andreas Bruckbauer <
[hidden email]> wrote:

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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”
> https://urldefense.proofpoint.com/v2/url?u=https-3A__www.confocal.nl_-23rcm2&d=DwIFaQ&c=kbmfwr1Yojg42sGEpaQh5ofMHBeTl9EI2eaqQZhHbOU&r=0LyF_z8oU1XGGyisIeOIXyIGIM5IYb3NcLjxHjUca5Y&m=aBnPuVl44CvsNnSHKnYuIZtIZCpEktGwklB9D7Cdvqg&s=FRdNlG-gKHQ7Lkl2vBS1jL6SlXxTyAMcF_pCXgVvfao&e=
>
> 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://urldefense.proofpoint.com/v2/url?u=https-3A__www.nature.com_articles_s41596-2D020-2D0313-2D9&d=DwIFaQ&c=kbmfwr1Yojg42sGEpaQh5ofMHBeTl9EI2eaqQZhHbOU&r=0LyF_z8oU1XGGyisIeOIXyIGIM5IYb3NcLjxHjUca5Y&m=aBnPuVl44CvsNnSHKnYuIZtIZCpEktGwklB9D7Cdvqg&s=WuqudKbziHqalUr5fiK7sSsr_CyQ63nsf-C6L2XiGYA&e=
> 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
>