Salt, 100x

Cyclops · Post by **Cyclops** » Fri Jun 09, 2017 1:36 pm

I just love playing with darkfield
I just wish sometimes I didn't get circular images. But then again I think it's not that much of an issue.

rjlittlefield · Post by **rjlittlefield** » Fri Jun 09, 2017 2:36 pm

I just wish sometimes I didn't get circular images.

Can you zoom the camera?

If not that, then of course you can crop to rectangular. That's what "real" camera interfaces do anyway.

--Rik

Pau · Post by **Pau** » Fri Jun 09, 2017 2:37 pm

I just wish sometimes I didn't get circular images

You need to use a longer focal lens. What camera and lens do you use?

You can also improve dark field illumination (note that the central part is much more illuminated than the periphery. Play with different DF stop sizes and with the condenser height.

Cyclops · Post by **Cyclops** » Fri Jun 09, 2017 4:12 pm

rjlittlefield wrote:
I just wish sometimes I didn't get circular images.
Can you zoom the camera?

If not that, then of course you can crop to rectangular. That's what "real" camera interfaces do anyway.

--Rik

Yes I can zoom, but at higher magnifications (if I swap the 10x eyepiece for the 20x) it just creates a larger dark area with a fuzzy inner edge containing the image in the centre.

Cyclops · Post by **Cyclops** » Fri Jun 09, 2017 4:15 pm

Pau wrote:
I just wish sometimes I didn't get circular images
You need to use a longer focal lens. What camera and lens do you use?

You can also improve dark field illumination (note that the central part is much more illuminated than the periphery. Play with different DF stop sizes and with the condenser height.

The camera is a Canon IXUS 265 HS compact, a very capable performer.

Cyclops · Post by **Cyclops** » Fri Jun 09, 2017 4:21 pm

This is another shot I took but this time I cropped to a rectangle

Pine Pollen by Larry Shone, on Flickr

Pau · Post by **Pau** » Sat Jun 10, 2017 1:33 am

Yes I can zoom, but at higher magnifications (if I swap the 10x eyepiece for the 20x) it just creates a larger dark area with a fuzzy inner edge containing the image in the centre

No, a 20X eyepiece makes things worse as yo have experienced. Just set the camera to a bit longer zoom, just enough to the round field limit disappear.
At the camera specification it says 25mm equivalent at wide angle. With a 10X eyepiece you want it to be around 60mm equivalent. In principle, if you do not have vignette issues it's better than cropping the image later.

discomorphella · Post by **discomorphella** » Mon Jun 12, 2017 12:31 am

If you can find a really optically perfect small NaCl crystal, you can get some very interesting internal reflections in darkfield.

David