Trinocular Projection Lenses for DSLRs

[LouiseScot]

Hi All
Just a follow-up post I actually got the Nikon CF 20x objective last Friday week but have been busy with other things. Anyway, I'm quite pleased with it. It does give sharper and higher resolution images than the generic lens so that's good.

I've just used some cheap Chinese slides - not the best, I know! Still, good enough to do a comparison. Camera used = Canon 1100d so some vignetting.

Generic woody plant stem:

GenericWoodyStem_28pc.jpg (131.86 KiB) Viewed 8656 times

Nikon version:

NikonWoodyStem28pc.jpg (148.46 KiB) Viewed 8656 times

Generic Lily Anther:

GenericLilyAnther_28pc.jpg (66.83 KiB) Viewed 8656 times

Nikon Lily Anther:

Nikon_LilyAnther_28pc.jpg (84.72 KiB) Viewed 8656 times

Nikon Lily Anther Parfocal:

Nikon_Lily_Par2_28pc.jpg (80.38 KiB) Viewed 8656 times

It's quite difficult to get the camera image parfocal with the Eyepieces. My judgement of focus isn't great. The parfocal Nikon image looks slightly better than the non-parfocal one - else it's just a slight difference of focus. I'd certainly buy a Nikon cf n 40x for my finite scope - if I could find one at a reasonable price.

Louise

[david_b]

In the woody stem example there is a lot more detail in the generic objective than the Nikon.
In the second example (lily, non-parfocal) there is more detail with the Nikon than the generic.
Suggesting another variable (like focus) needs to be eliminated for an effective comparison.

[LouiseScot]

In the woody stem example there is a lot more detail in the generic objective than the Nikon.
In the second example (lily, non-parfocal) there is more detail with the Nikon than the generic.
Suggesting another variable (like focus) needs to be eliminated for an effective comparison.

Well, it's really only for my own benefit. I think, certainly with the Lily, the Nikon is much better in terms of resolution and sharpness. The stem cross section is harder to focus on and, as I said, my judgement of focus isn't great. Overall, from using it, I'd say the Nikon is better. It would be remarkable if it wasn't!

Louise

[Hobbyst46]

IMHO, judging from the first pair (the stem), and actually from also from the other pair (generic vs parfocal Nikon), the Nikon yields a much more planar image, even considering its somewhat narrower FOV relative to the generic.
Under optimized illumination, I believe the Nikon will give better contrast as well.

[MichaelG.]

Looks very encouraging, to me, Louise

Keep up the good work, and do whatever you can to optimise the image distance for the Nikon.

MichaelG.

[david_b]

I question how the Nikon image can be considered better in the first pair.

Details of the woody stem image:

Generic:

Screen Shot 2020-08-09 at 14.50.48.png (54.51 KiB) Viewed 8631 times

Nikon:

Screen Shot 2020-08-09 at 14.51.08.png (46.39 KiB) Viewed 8631 times

[mrsonchus]

Hmm, an interesting comparison but the setup isn't quite good enough to make it valid. The slides aren't so bad, the woody one has some interesting features in cluding 'expanded ray' tissue - a product of fast post-1st year growth where the rays have to grow 'sideways' to keep up with the rapid increase in the stem's size....

[MichaelG.]

I question how the Nikon image can be considered better in the first pair.

Details of the woody stem image:

.

I think you may have chosen the one area where it’s questionable, David
... Most of the Nikon image looks much crisper to me, and I would posit that your sampled area is simply out-of-focus on the Nikon image [the rest of it being sufficiently good to make that obvious ... which is not the case on the generic objective].

MichaelG.

.

Super-flat test slide required please, Louise

[david_b]

I think you may have chosen the one area where it’s questionable, David
... Most of the Nikon image looks much crisper to me, and I would posit that your sampled area is simply out-of-focus on the Nikon image [the rest of it being sufficiently good to make that obvious ... which is not the case on the generic objective].

MichaelG.

.

Super-flat test slide required please, Louise

Yes, that's why I said,

another variable (like focus) needs to be eliminated for an effective comparison

[MichaelG.]

I think you may have chosen the one area where it’s questionable, David
... Most of the Nikon image looks much crisper to me, and I would posit that your sampled area is simply out-of-focus on the Nikon image [the rest of it being sufficiently good to make that obvious ... which is not the case on the generic objective].

MichaelG.

.

Super-flat test slide required please, Louise

Yes, that's why I said,

another variable (like focus) needs to be eliminated for an effective comparison

.
But you also said:

In the woody stem example there is a lot more detail in the generic objective than the Nikon.

So let’s just agree that a better test slide is required.

MichaelG.

[LouiseScot]

Thanks for all the replies. Just to say, my current T2 microscope adapter sits a bit too high to be parfocal with the eyepieces, even with a low-profile T-ring. I could saw off some of the adapter length but I would almost certainly end up with a jagged end... (I don't even have a vice to hold it!). So I'll try making a 3d printed one first. At the same time I'm unsure how much difference to image quality a cm or so beyond the theoretical intermediate image plane really makes? I couldn't see much difference between the two with the Nikon lily above. I think the only way I'd get all of that woody stem in focus would be with focus stacking. I'll be able to do that much better with the extreme macro setup I plan to use. Of course, I won't know how well that will work until it's up and running and I've tried it out... Meanwhile, I'm waiting to have cataract operations - the first instalment has been delayed because of the Covid-19 . Hopefully my eyesight will improve a bit post-op!

Louise

[MichaelG.]

... I'm unsure how much difference to image quality a cm or so beyond the theoretical intermediate image plane really makes?
[…]
... Meanwhile, I'm waiting to have cataract operations - the first instalment has been delayed because of the Covid-19 . Hopefully my eyesight will improve a bit post-op!

Louise

.

(a) I’m afraid you probably won’t know until you try it

(b) Best wishes for the cataract ops ... mine were a wonderful transformation.

MichaelG.

[Hobbyst46]

Thanks for all the replies. Just to say, my current T2 microscope adapter sits a bit too high to be parfocal with the eyepieces, even with a low-profile T-ring. I could saw off some of the adapter length but I would almost certainly end up with a jagged end... (I don't even have a vice to hold it!). So I'll try making a 3d printed one first. At the same time I'm unsure how much difference to image quality a cm or so beyond the theoretical intermediate image plane really makes?...

Although not in line with your original purpose of projection, the "fact" that the Nikon visually performs better than the generic leaves open the alternative of direct projection with an eyepiece. Namely, that the eyepiece is raised above the tube rim by a few mm. And the camera (without lens) positioned on top. Might work, without having to shorten or replace the photo tube.

[LouiseScot]

... I'm unsure how much difference to image quality a cm or so beyond the theoretical intermediate image plane really makes?
[…]
... Meanwhile, I'm waiting to have cataract operations - the first instalment has been delayed because of the Covid-19 . Hopefully my eyesight will improve a bit post-op!

Louise

.

(a) I’m afraid you probably won’t know until you try it

(b) Best wishes for the cataract ops ... mine were a wonderful transformation.

MichaelG.

a) I did - see 2nd Nikon lily pic
b) thanks! I just don't know when it will be...

Louise

[LouiseScot]

Thanks for all the replies. Just to say, my current T2 microscope adapter sits a bit too high to be parfocal with the eyepieces, even with a low-profile T-ring. I could saw off some of the adapter length but I would almost certainly end up with a jagged end... (I don't even have a vice to hold it!). So I'll try making a 3d printed one first. At the same time I'm unsure how much difference to image quality a cm or so beyond the theoretical intermediate image plane really makes?...

Although not in line with your original purpose of projection, the "fact" that the Nikon visually performs better than the generic leaves open the alternative of direct projection with an eyepiece. Namely, that the eyepiece is raised above the tube rim by a few mm. And the camera (without lens) positioned on top. Might work, without having to shorten or replace the photo tube.

It will be easier to make a new adapter. It's not a tube as such- it's just one of these https://www.365astronomy.com/Microscope ... hread.html
else maybe I could get a shorter one from somewhere.

Louise

[mrsonchus]

I think I have one of those in my drawer - I have a look at it after tea.

[MichaelG.]

a) I did - see 2nd Nikon lily pic

My apologies, Louise ... I evidently misinterpreted this:

... Just to say, my current T2 microscope adapter sits a bit too high to be parfocal with the eyepieces, even with a low-profile T-ring. […]

MichaelG.

[LouiseScot]

Um, re: the adapter: the 22mm dia 'tube' part of the T2 microscope adapter is about 25mm long but there is a lip in the microscope tube at a depth of about 12mm. Currently the sensor plane is at ~154mm rather than 150mm. So I need the adaptor to be 4-5mm shorter I'll have a go at 3D printing one tomorrow Printing threads is always a bit challenging though..
I managed to set up the camera to be parfocal for the 2nd Nikon lily anther image just by using a couple of circular/ring spacers without the adapter and the Canon balanced precariously atop - but it's not stable like that...

Louise

[MichaelG.]

I managed to set up the camera to be parfocal for the 2nd Nikon lily anther image just by using a couple of circular/ring spacers without the adapter and the Canon balanced precariously atop - but it's not stable like that...

Louise

Aha ! ... got it now

MichaelG.

[LouiseScot]

[LouiseScot]

Designed and printed a new dslr adapter earlier. I made it an M42 x 1 rather than T2 as it's easier to print reliably. Works a treat! It's within a smidgeon of being parfocal with the eyepieces. I've not tried very hard to get it exact . Here is another shot of the lily anther, albeit a different part. It seems good to me.

Nikon_Lily_newAdapt27pc.jpg (97.24 KiB) Viewed 8490 times

Louise

[apochronaut]

You still need a better test slide. Something of high contrast and spanning the entire field. Additionally, your background shows a high degree of diffraction shading , radiating inwards from the periphery despite the visual plane and the sensor plane being parfocal. How is your condenser set up?

Usually the microscope field is increased relative to the sensor border, so that the sensor frame covers the maximum possible field ; i.e. the corners abut the field stop but the background unevenness won't allow a that level of maximum field coverage in your case.
Bringing the sensor borders in, will throw your parfocality off. Your current parfocality condition demands cropping.

[LouiseScot]

You still need a better test slide. Something of high contrast and spanning the entire field. Additionally, your background shows a high degree of diffraction shading , radiating inwards from the periphery despite the visual plane and the sensor plane being parfocal. How is your condenser set up?

Usually the microscope field is increased relative to the sensor border, so that the sensor frame covers the maximum possible field ; i.e. the corners abut the field stop but the background unevenness won't allow a that level of maximum field coverage in your case.
Bringing the sensor borders in, will throw your parfocality off. Your current parfocality condition demands cropping.

Thanks -

"Additionally, your background shows a high degree of diffraction shading , radiating inwards from the periphery" What's that??

I'm set up with Kohler Illumination and the condenser racked up. Illumination is from a 20W halogen bulb via a blue filter. I could have cropped the image but didn't bother for this. I'm not that concerned about using a better test slide - this image was taken just to show the use of the new adapter I made today, and which allows lowering the sensor plane to very close to the desired 150mm mark. I'm not sure how to get it exact - I just used a ruler and my eyes to measure it. Anyway, I get better images with the Nikon objective than with the generic plan achros, so that's all I care about for now.

Louise

[apochronaut]

I must have missed what magic takes place at 150mm?

[LouiseScot]

I must have missed what magic takes place at 150mm?

No magic, it's just the position of the intermediate image plane in a 160mm finite tube.

Louise

[apochronaut]

150mm is for an optic, not a sensor. Your image circle is smaller than your sensor and there is an enormous amount of shading off or vignetting. I' m not sure the condenser is responsible for that.

[LouiseScot]

150mm is for an optic, not a sensor. Your image circle is smaller than your sensor and there is an enormous amount of shading off or vignetting. I' m not sure the condenser is responsible for that.

I was led to believe the intermediate image position did make a difference to the image quality... In any case, it's convenient if the eyepieces and the camera are parfocal.
Of course there's vignetting - the tube diameter is small for a dslr. But I'm not too worried about it - in principle I could compensate for it.
Here's a higher contrast image. Unfortunately, there is some tilt and I'm not sure how to properly fix that. I'll have to just have a fiddle.

NikonGraticule27pc.jpg (59.08 KiB) Viewed 8450 times

Louise

[MichaelG.]

Brilliant result, Louise !!

Everything you could reasonably hope for.

Q.E.D.

MichaelG.

[LouiseScot]

Brilliant result, Louise !!

Everything you could reasonably hope for.

Q.E.D.

MichaelG.

Thanks. Hopefully I'll be able to find a way to correct what appears to be a slight tilt.
Louise

[mrsonchus]

That's not a 'tilt' - it's merely that the head isn't quite turned to the right position to line up. Just turn the head very slightly to make the line horizontal as it were - no problem there! It'll be a tiny amount either CW or ACW of course.