For when you need to get that little bit closer.....

[JMC]

I recently picked up a couple of Thorlabs LMU UVB microspot focusing objectives (15x and 40x) as, well, the price was right. I thought they may be useful to make into condensers for my microscope. As they are setup for infinity tubes though, I can mount them in front of another lens on a camera and use them for imaging directly. So, for when the UV Rayfact 105mm isn't quite getting me close enough, I now have other options...

 

 

 

In combination with the 105mm lens there is some severe vignetting on a full frame sensor. This would be much better on a 200mm lens, but then I don't have a 200mm lens for UVB imaging (although I see Thorlabs do make them for infinity tube microscopes).

 

Details on them LMU objectives in case it is of interest - https://www.thorlabs...ctgroup_id=3271

[Andy Perrin]

ThorLabs is addictive. They get you with their “everything attaches to everything else” system and by feeding you treats.

[Stefano]

Can a lens be extended with a helicoid to the point where it becomes a microscope? What are the disadvantages?

[Andrea B.]

That looks very cool. I would love to see a photo made with it.

 

Can't you reset the frame size in the Canon? Like to a DX mode or 1:1 format? That would help a bit with the vignetting perhaps?

[dabateman]

Can a lens be extended with a helicoid to the point where it becomes a microscope? What are the disadvantages?

 

No it can't. You will run into minimum focus issues due to the length of the lens.

 

For Macro you can add a tube, limited by physical lens.

 

Reverse mount a wide angle lens. This is fun and both the Sigma 10-20mm f4/5.6 and the Sigma 17-70mm f2.8/4 lenses work reversed with an EF mount adapter. I now have 5x to 10x magnification with the 10-20mm and 1.8x to 5x magnification with the 17-70mm. Also with the auto Ef mount adapter I have in camera focus stacking.

 

You can reverse mount a wide angle in front of a telephoto lenses. So 24mm in front of 100mm lens will give you 4x magnification.

 

You can use a teleconverter to give you some magnification.

 

You can add a macro lens like Raynox 250 in front of your lens. This is usually just a single or dual element lens. Similarly you can add a 50mm focal length fused silica element in front of JMC's 105mm to get some magnification.

 

 

[Stefano]

Thanks. I didn't know there was a limit. I have a USB camera with a lens you can screw/unscrew to change focus, and if you unscrew it a lot the focus gets very close. I was able to see the individual pixels on my smartphone display, for example.

[dabateman]

Yes just think about it. You can move it forward to a point where the in focus point is in the first element of the lens. At that point it doesn't work so well.

 

This will depend on the lens. My old Sigma 30mm f1.4 four thirds lens can be used with the Olympus Ex-25 tube, as the physical lens is not too long. But the Panasonic 25mm f1.4 was too long and couldn't be used with that tube.

[Cadmium]

Jonathan, Pretty cool! Thanks!

[ulf]

Can a lens be extended with a helicoid to the point where it becomes a microscope? What are the disadvantages?

No this objective is designed to work together with a tube lens. It is an infinite conjugate design needing more optics in the light path.

 

You can identify such microscope lenses by th infinity mark, printed on their barrel: https://www.thorlabs...LMU-15X_SGL.jpg

 

Look here about infinite conjugate design:

https://www.edmundop...and-objectives/

Scroll down to fig 12.

 

You get some miss match if the tube lens has wrong FL, but it still works. They are designed for a 200mm FL tube lens and Jonathan used his UV-nikkor instead.

 

I have done the same for microscope lenses in VIS, mounting them in front of camera lenses.

 

I do not fully understand Davids answer above.

[Cadmium]

I would like to see some example shots, including the full vignetting.

[dabateman]

Ulf my interpretation of Stefano's question was:

"can't Jonathan just add 400mm to 800mm of extension tubes to his Rayfact 105mm lens and have an equivalent 15x microscope objective? "

My answer no .

Then I mentioned all the ways to get magnification or make various objective like optics using the lenses you already have. Like flipping them, extending them or adding a macro element.

 

I didn't interpret the question like you thinking about microscope objectives. In that the answer is it depends. An infinity corrected microscope objective, No, it will need a back lens like Jonathan has. The Panasonic 100-300mm works great on a m43rds system for most infinity correction objectives.

 

If its a 160/0 or 240/0 or x/y objective, then Yes. The x is the tube length and the y is coverslip correction number. So a typical RMS objective that says 160/0.17 will just need a 160mm tube in front of your camera and expects to see a 0.17 mm coverslip between your sample. You can get 0 correction or objectives with a ring to dial in a range from 0 to 2mm correction, like my Nikon 40x objective.

[JMC]

All, yes these infinity corrected objectives need to be used in conjunction with another lens (normally a 200mm one).

 

Not sure about in camera cropping on the Canon. I'll try and get some UV shots with it when I have a minute. Obviously it has a depth of field like a razor blade though, so will need to get something set up to get some photos with it. Plus the working distance is very very short, so will need to think about lighting too.

[ulf]

Ulf my interpretation of Stefano's question was:

"can't Jonathan just add 400mm to 800mm of extension tubes to his Rayfact 105mm lens and have an equivalent 15x microscope objective? "

My answer no .

Then I mentioned all the ways to get magnification or make various objective like optics using the lenses you already have. Like flipping them, extending them or adding a macro element.

 

I didn't interpret the question like you thinking about microscope objectives. In that the answer is it depends. An infinity corrected microscope objective, No, it will need a back lens like Jonathan has. The Panasonic 100-300mm works great on a m43rds system for most infinity correction objectives.

 

If its a 160/0 or 240/0 or x/y objective, then Yes. The x is the tube length and the y is coverslip correction number. So a typical RMS objective that says 160/0.17 will just need a 160mm tube in front of your camera and expects to see a 0.17 mm coverslip between your sample. You can get 0 correction or objectives with a ring to dial in a range from 0 to 2mm correction, like my Nikon 40x objective.

Thanks for the for me more clear answer. I fully agree.

I might add to that, that de quality demand of the camera lens used as a tube lens is not very high as the light path is similar to a quite stopped down lens. I could successfully use a kit lens zoom for my mitutoyo microscope lens on my Canon EOS 450D I used then.

 

Also the tube length for finite conjugate microscope lenses can be stretched a bit and must not be exactly right at 160 or 210mm.

Many of those older lenses had the chromatic correction divided between eyepiece and objective. The Nikon Plan lenses did not, keeping all corrections in the objective.

[JMC]

Some rather quick and dirty experiments to show what the images looks like. Camera - UV converted Nikon d810 (ACS UV filter inside the camera). Lens - UV Rayfact 105mm wide open at f4.5 and focused to infinity. Front objective lens - Thorlabs 15x LMU UVB. Light source - single Nemo 365nm torch. Captured as raw in camera and whitebalanced in Darktable. Camera on a tripod and subject positioned manually using live view and a steady hand......

 

Note - there's no stacking here, these are single images hence the extremely shallow depth of field.

 

First, Dandelion flower head.

 

 

Second, a feather.

 

 

This very overexposed image gives you an idea of the vignetting at the edges on a full frame sensor image.

 

Working distance was about 5mm.

[colinbm]

Very neat Jonathan, huge potential with stacking.....

[dabateman]

Those images look good. Not much Vignetteing actually. You have more than a 1:1 crop. You could easily crop maybe 5:4, for my favorite print size of 8x10.

[JMC]

Thanks and yes, the vignetting was not as bad as I initially thought.

[dabateman]

Jonathan I highly recommend picking up one of these before there all gone:

https://www.amazon.com/dp/B01DFWXTD4/ref=cm_sw_r_cp_apa_glt_fabc_JH36WVF30HK5K117ASK7?_encoding=UTF8&psc=1

 

The official Meike site says they are out of production. It allows you to electronically reverse mount a Canon EF lens to your camera or really any mirrorless camera.

The 40mm STM f2.8 works well for autofocus stacking in UVA. You can use a program like DigiCamera control to control your stack automatically.

http://digicamcontrol.com/

 

For Stefano you can get a used Canon 18-55mm STM for $60, get this reverse mount adapter for $50-$60 and add a EF-M to Ef adapter and you will have an autofocus 1-5x magnification lens that is quite good. I went with a Sigma 17-70mm as I know it was flat field reversed (I have one in SA mount), can focus past infinity for added working distance and can see from 380nm up. I don't know if the 18-55mm Canon can see UVA.

But if you look through this persons macro images it works very nicely:

 

 

 

[Stefano]

With my Soligor + helicoid this is how far I can zoom (last three images): https://www.ultravioletphotography.com/content/index.php/topic/4435-some-bees-on-dandelions/page__view__findpost__p__43619

 

I should be able to extend the lens a little more, so this is not the theoretical limit.

[colinbm]

Thanks for the heads up Dave, I am loving the Canon 40mm pancake on the Sigma fp.

[dabateman]

Yes with the reversed 40mm STM f2.8 lens I see 12mm across the sensor. So if it is 17.4mm wide than thats 1.45 magnification.

 

[Andrea B.]

JMC, thank you for the photo examples.