Beck 36x / 0.5 reflex objective

jmc · Post by **jmc** » Tue Jun 02, 2020 8:16 am

Following on from my previous thread on the Beck 52x reflex objective (here, https://www.photomacrography.net/forum/ ... hp?t=41751), I've also found a Beck 36x 0.5 reflex objective. This one turned up in a nice wooden Beck box, and came with the 2 adjustment Allen keys (the silver knobs in the image of the inside of of the box).

As with the 52x it is RMS threaded, and like the 52x the thickness of the coverslip can be adjusted for, although on this one the scale is in inches. Also, the tube length doesn't seem to be adjustable as it could be on my 52x.

Amazingly this needed very little adjustment when put on my Olympus BHB. The image below is of a Corn seed pre-prepared slide, imaged through 10x eyepiece objective with a camera phone. The actual image through the eyepiece looks a bit sharper than this, I think the phone does some weird HDR processing when trying to use it for eyepiece shots.

My main interest in these is for UV imaging, and both the 36x and 52x show good UV transmission, even down to 280nm.

I suspect the absolute transmission for both lenses is a little higher than shown here, as it's hard to get a measurement through such a small diameter objective with my setup.

enricosavazzi · Post by **enricosavazzi** » Tue Jun 02, 2020 11:02 am

Perhaps you already know, but there are a few old papers (mid-20th century) dealing with reflective microscope objectives in UV, for example:

https://onlinelibrary.wiley.com/doi/abs ... m%3Apubmed

https://pubmed.ncbi.nlm.nih.gov/13118588/
This one has sample images taken with a Beck reflecting objective, albeit probably not yours.

https://www.researchgate.net/publicatio ... al_Mirrors

Macro_Cosmos · Post by **Macro_Cosmos** » Tue Jun 02, 2020 11:34 am

Very interesting objective! I have an EO reflex objective that's designed for 200-10,000nm wavelength, UV and well into IR. I should make a dedicated diffuster and give it a go.

ray_parkhurst · Post by **ray_parkhurst** » Tue Jun 02, 2020 1:30 pm

From my experience with the 36x and 15x reflecting objectives, the size of the front aperture is of utmost importance for good results. I see in your photos that the front aperture on your 36x objective is quite a bit larger than mine, and interestingly, the one on your 52x appears to be the same as my 36x. I would suggest trying the smaller aperture on your 36x to see if it will improve the IQ.

jmc · Post by **jmc** » Wed Jun 03, 2020 1:53 am

Thanks Enrico. Unfortunately most of those I can't access, but will keep them until I'm next working with someone who has article access.

Macro_Cosmos, remember I'm using it for transmission work. Someone on here did try one for reflection work, and didn't have much success. From what I have seen they are more suited to transmission work.

Ray, my 52x has a 4.5mm diameter hole, and the 36x is about 10.4mm. I believe they are removable on mine. So if I can remove and replace them I'll give that a go.

Macro_Cosmos · Post by **Macro_Cosmos** » Wed Jun 03, 2020 3:53 am

jmc wrote:Thanks Enrico. Unfortunately most of those I can't access, but will keep them until I'm next working with someone who has article access.

Macro_Cosmos, remember I'm using it for transmission work. Someone on here did try one for reflection work, and didn't have much success. From what I have seen they are more suited to transmission work.

Ray, my 52x has a 4.5mm diameter hole, and the 36x is about 10.4mm. I believe they are removable on mine. So if I can remove and replace them I'll give that a go.

I've tried it for reflected light, it's alright.
I just wish there's a 5x one to use in the field, the doughnut shaped diffusion orbs would be a fun addition to any photo! 15x is too much hassle.

I usually use my 10x and 5x for transmitted light, I should definitely give the 15x a go too. I wonder if there's a case for transmitted UV/IR... or if there's any specimens that will benefit from the wide transmission of these reflex objectives. They are lovely to look at.

jmc · Post by **jmc** » Wed Jun 03, 2020 4:03 am

Macro_Cosmos wrote:I've tried it for reflected light, it's alright.
I just wish there's a 5x one to use in the field, the doughnut shaped diffusion orbs would be a fun addition to any photo! 15x is too much hassle.

I usually use my 10x and 5x for transmitted light, I should definitely give the 15x a go too. I wonder if there's a case for transmitted UV/IR... or if there's any specimens that will benefit from the wide transmission of these reflex objectives. They are lovely to look at.

Ah right, good to know you're tried it for reflected work and got it to work.

I do work on skin research, and have a few ideas around the use of transmitted UV microscopy for that, which I am hoping to try out once I have all the kit.

ray_parkhurst · Post by **ray_parkhurst** » Wed Jun 03, 2020 7:49 am

jmc wrote: Ray, my 52x has a 4.5mm diameter hole, and the 36x is about 10.4mm. I believe they are removable on mine. So if I can remove and replace them I'll give that a go.

The aperture on my 36x measures 4.5mm.

Lou Jost · Post by **Lou Jost** » Wed Jun 03, 2020 9:59 am

I'd like to try one with epi UV lighting for fluorescence. A major limitation of standard objectives is their low UV transmission. The purely reflecting objectives would have very high transmission.