Swift Achromat vs Nikon Fluor

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LouiseScot
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Swift Achromat vs Nikon Fluor

#1 Post by LouiseScot » Thu Mar 25, 2021 3:54 pm

Hi

I received a Nikon CF Fluor 40x/0.85 from Japan yesterday so thought I'd post a comparison with the Swift 40x/0.65 achromat. As my scope is currently set up for darkfield I thought I'd leave it like that for now, though I may not necessarily be getting the best from the high NA fluor. I don't really have the experience to judge these things. Light source is a 10W warm white LED but still using the Swift 'beehive' illuminator.
Anyway, here is a direct comparison between the two objectives using my trusty Pleurosigma formosum vintage slide:

Pleuro_Swift40x_NikonFluor_40x.jpg
Pleuro_Swift40x_NikonFluor_40x.jpg (61.33 KiB) Viewed 1466 times



Both images cropped to 50%. I was pleased to see there was a difference! The Nikon cost me $295 which is about the same as the Swift380T cost me last year! Still, I think the Nikon has potential. Not sure if I'm getting increased resolution here but there's certainly less CA. I still think the Swift achromat is very good. I will try the new fluor out in brightfield/oblique soon.

There is a paper with data and SEM for the Pleurosigma here:https://www.researchgate.net/publicatio ... lariophyta if anyone is interested (you can download the .pdf).

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Hobbyst46
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Re: Swift Achromat vs Nikon Fluor

#2 Post by Hobbyst46 » Fri Mar 26, 2021 3:58 pm

Very nice comparison. Here the Nikon shows a slight advantage but probably in BF it will be more prominent.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

viktor j nilsson
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Re: Swift Achromat vs Nikon Fluor

#3 Post by viktor j nilsson » Fri Mar 26, 2021 4:56 pm

Clear advantage for the Fluor. However, it does looks a little hazy, which looks a lot like spherical aberration to me. How carefully did you optimize the correction collar setting? At 0.85 it needs to be set quite precisely to minimize spherical aberrations. It's a very nice objective, and pretty easy to use. I think you'll like it a lot.

It could also just be that darkfield is really finicky at these NAs. Would be interesting to see a brightfield comparison.

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Re: Swift Achromat vs Nikon Fluor

#4 Post by LouiseScot » Fri Mar 26, 2021 5:41 pm

viktor j nilsson wrote:
Fri Mar 26, 2021 4:56 pm
Clear advantage for the Fluor. However, it does looks a little hazy, which looks a lot like spherical aberration to me. How carefully did you optimize the correction collar setting? At 0.85 it needs to be set quite precisely to minimize spherical aberrations. It's a very nice objective, and pretty easy to use. I think you'll like it a lot.

It could also just be that darkfield is really finicky at these NAs. Would be interesting to see a brightfield comparison.
Hi Viktor

I didn't actually adjust the collar at all! I did think about it but was in a rush. Being a vintage slide, I had no idea how thick the coverslip might be? I should have just tried some settings either side of the nominal 0.17 .
I've switched over to brightfield but it's tricky trying to get decent contrast even with oblique illumination. I may need to fine tune the condenser. The fluor does show a lot of what I call 'flaring'. Again, I probably need to adjust the illumination. I'll have another go tomorrow and with other diatom slides :)

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#5 Post by viktor j nilsson » Fri Mar 26, 2021 6:34 pm

LouiseScot wrote:
Fri Mar 26, 2021 5:41 pm
viktor j nilsson wrote:
Fri Mar 26, 2021 4:56 pm
Clear advantage for the Fluor. However, it does looks a little hazy, which looks a lot like spherical aberration to me. How carefully did you optimize the correction collar setting? At 0.85 it needs to be set quite precisely to minimize spherical aberrations. It's a very nice objective, and pretty easy to use. I think you'll like it a lot.

It could also just be that darkfield is really finicky at these NAs. Would be interesting to see a brightfield comparison.
Hi Viktor

I didn't actually adjust the collar at all! I did think about it but was in a rush. Being a vintage slide, I had no idea how thick the coverslip might be? I should have just tried some settings either side of the nominal 0.17 .
I've switched over to brightfield but it's tricky trying to get decent contrast even with oblique illumination. I may need to fine tune the condenser. The fluor does show a lot of what I call 'flaring'. Again, I probably need to adjust the illumination. I'll have another go tomorrow and with other diatom slides :)

Thanks

Louise
I never really bother reading the scale, you always need to find the best setting based on what you see through the eyepieces anyway. I just rotate it back and forth until I find the sweet spot, then try small changes in either direction to find the ideal setting. For me there's usually a small span that visually looks almost as good, but if you really focus on some minute detail you can usually find the exact spot that gives you a little bit of extra detail. Well, at least with be 40x 0.95, the 40x.85 is a little more forgiving. It's worth practicing, it took me a while before I felt I could reliably find the best setting.

LouiseScot
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Re: Swift Achromat vs Nikon Fluor

#6 Post by LouiseScot » Fri Mar 26, 2021 6:44 pm

viktor j nilsson wrote:
Fri Mar 26, 2021 6:34 pm
LouiseScot wrote:
Fri Mar 26, 2021 5:41 pm
viktor j nilsson wrote:
Fri Mar 26, 2021 4:56 pm
Clear advantage for the Fluor. However, it does looks a little hazy, which looks a lot like spherical aberration to me. How carefully did you optimize the correction collar setting? At 0.85 it needs to be set quite precisely to minimize spherical aberrations. It's a very nice objective, and pretty easy to use. I think you'll like it a lot.

It could also just be that darkfield is really finicky at these NAs. Would be interesting to see a brightfield comparison.
Hi Viktor

I didn't actually adjust the collar at all! I did think about it but was in a rush. Being a vintage slide, I had no idea how thick the coverslip might be? I should have just tried some settings either side of the nominal 0.17 .
I've switched over to brightfield but it's tricky trying to get decent contrast even with oblique illumination. I may need to fine tune the condenser. The fluor does show a lot of what I call 'flaring'. Again, I probably need to adjust the illumination. I'll have another go tomorrow and with other diatom slides :)

Thanks

Louise
I never really bother reading the scale, you always need to find the best setting based on what you see through the eyepieces anyway. I just rotate it back and forth until I find the sweet spot, then try small changes in either direction to find the ideal setting. For me there's usually a small span that visually looks almost as good, but if you really focus on some minute detail you can usually find the exact spot that gives you a little bit of extra detail. Well, at least with be 40x 0.95, the 40x.85 is a little more forgiving. It's worth practicing, it took me a while before I felt I could reliably find the best setting.
Thanks for the advice and the pointers! I'll have a go tomorrow. I'll probably find it easier with the Mediterranean diatom slide I have :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#7 Post by viktor j nilsson » Fri Mar 26, 2021 6:54 pm

LouiseScot wrote: Thanks for the advice and the pointers! I'll have a go tomorrow. I'll probably find it easier with the Mediterranean diatom slide I have :)

Louise
Good luck!
And yes, even with the collar I think it's better to judge its performance on a modern slide with a cover slip that's close to 0.17

Sir
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Re: Swift Achromat vs Nikon Fluor

#8 Post by Sir » Sat Mar 27, 2021 5:33 am

When considering the performance between these objectives, how much influence does the microscope itself have on the image quality?

E.g. if you did this comparison in reverse by putting both objectives on a Nikon microscope, would the differences be similar?

LouiseScot
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Re: Swift Achromat vs Nikon Fluor

#9 Post by LouiseScot » Sat Mar 27, 2021 10:21 am

Sir wrote:
Sat Mar 27, 2021 5:33 am
When considering the performance between these objectives, how much influence does the microscope itself have on the image quality?

E.g. if you did this comparison in reverse by putting both objectives on a Nikon microscope, would the differences be similar?
I suppose a different/better DF condenser might make a difference (I'm using a retrofitted AmScope dry one here). Perhaps similarly with a different light source. The cf objective doesn't require any correction. A different operator could make a world of difference - especially one with better eyesight!
As pointed out by Viktor, adjusting the Nikon collar would probably improve the Nikon objective result. I'll be trying that over the weekend :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#10 Post by viktor j nilsson » Sat Mar 27, 2021 10:30 am

One other thing that's really critical with a dry NA 0.85 objective is to get the tube length exactly right. You're not using this with your astronomical eyepiece, are you? Did you manage to get that to be perfectly parfocal with your viewing eyepieces? If your photo eyepiece is off even by 2mm, image quality of going to suffer dramatically at NA 0.85.

This objective would likely work really well with the cheap 10x/22 eyepieces Scarodactyl has tested, btw.

LouiseScot
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Re: Swift Achromat vs Nikon Fluor

#11 Post by LouiseScot » Sat Mar 27, 2021 10:38 am

viktor j nilsson wrote:
Sat Mar 27, 2021 10:30 am
One other thing that's really critical with a dry NA 0.85 objective is to get the tube length exactly right. You're not using this with your astronomical eyepiece, are you? Did you manage to get that to be perfectly parfocal with your viewing eyepieces? If your photo eyepiece is off even by 2mm, image quality of going to suffer dramatically at NA 0.85.

This objective would likely work really well with the cheap 10x/22 eyepieces Scarodactyl has tested, btw.
Yes, am using the astro EP but everything is parfocal - why does the tube length make such a difference? Surely, if it's in focus... ?

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#12 Post by viktor j nilsson » Sat Mar 27, 2021 10:49 am

If your regular eyepieces are seated exactly where they are supposed to be, and your photo eyepiece and camera setup is parfocal with the viewing eyepieces, then you are very close to the correct tube length.

Tolerance to tube length deviations is highly dependent on NA. At low NA, you can change the tube length by several cm. But as you approach NA 1.00, the acceptable deviation is on the scale of a single mm.

See this graph:
Image

And this recent discussion:
https://www.photomacrography.net/forum/ ... =8&t=43222

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Re: Swift Achromat vs Nikon Fluor

#13 Post by LouiseScot » Sat Mar 27, 2021 11:07 am

I don't pretend to understand the optics... However, I'm imaging afocally. So, currently, I have the same eyepieces as oculars and as projection. Camera is a Canon 1100d with the 18-55 kit lens set to 35mm. It's not a great camera lens but, as it happens, I'm expecting a Canon 50mm f1.8 to be delivered today, so looking forward to seeing whether that makes any difference. Image fov will be smaller at 50mm. Also, I'm using the camera tethered, and I'm fine tuning the focus via the computer screen, if needed. As mentioned, my eyes and my judgement aren't the best either... The fluor doesn't have as much depth of focus as the achromat so focusing gets critical and one part of the Pleurosigma may be in focus whilst the edge, for example, is not.
I just did some adjustments of the Nikon collar. I could obviously tell where it went a bit crazy but subtle differences and changes I'm not so good at.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#14 Post by viktor j nilsson » Sat Mar 27, 2021 1:20 pm

Oh, but if you are using the same eyepieces for viewing and photographing, then it's very possible that you're picking up the image at a different focal plane than where it should be. Do you have any "real" eyepieces to compare with? They don't need to be optically matched to the Nikon objectives, almost any 160mm finite eyepiece will work as almost all of them are designed to pick up the image 10mm down the tube (the DIN standard).

If you switch back and forth between the astro eyepiece and a regular DIN microscope eyepiece, are they perfectly parfocal? If they are not, then you have changed the tube length, and will get a much poorer image with the 40x 0.85 objective than what it's capable of producing.

Edit: and if your tube length is off by more than a mm or two, I expect that the aberrations caused by the tube length mismatch will be so pronounced that it will be difficult to find the best collar setting.

Now that you have such nice glass, I think it would be wise to get some of those 10x/22 eyepieces that have been found to work well with Nikon optics.

LouiseScot
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Re: Swift Achromat vs Nikon Fluor

#15 Post by LouiseScot » Sat Mar 27, 2021 2:28 pm

viktor j nilsson wrote:
Sat Mar 27, 2021 1:20 pm
Oh, but if you are using the same eyepieces for viewing and photographing, then it's very possible that you're picking up the image at a different focal plane than where it should be. Do you have any "real" eyepieces to compare with? They don't need to be optically matched to the Nikon objectives, almost any 160mm finite eyepiece will work as almost all of them are designed to pick up the image 10mm down the tube (the DIN standard).

If you switch back and forth between the astro eyepiece and a regular DIN microscope eyepiece, are they perfectly parfocal? If they are not, then you have changed the tube length, and will get a much poorer image with the 40x 0.85 objective than what it's capable of producing.

Edit: and if your tube length is off by more than a mm or two, I expect that the aberrations caused by the tube length mismatch will be so pronounced that it will be difficult to find the best collar setting.

Now that you have such nice glass, I think it would be wise to get some of those 10x/22 eyepieces that have been found to work well with Nikon optics.
Ah, I think I'm beginning to understand what you're getting at. If I'm correct, you're saying that it's not enough that all three eyepieces are parfocal, but they have to be parfocal at exactly 160mm? I didn't think the tube length was that critical - I thought it only influenced magnification? So if you used, say, a tube length of 180mm everything would be fine but you'd just get a relatively higher magnification i.e. (180/160)x = 1.125x = 40x1.125 = 45x for a nominal 40x objective? It's difficult to check a standard 10x EP in my modified trinocular tube which has been changed to hold an 1.25" astro EP. What I can do is put a standard 10x EP in the microscope EP holder, focus, then adjust the trinocular astro EP to be parfocal by eye (as best as I can!). Would that be sufficient? If not, I'll have to re-engineer things a bit :)

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#16 Post by viktor j nilsson » Sat Mar 27, 2021 2:49 pm

LouiseScot wrote: Ah, I think I'm beginning to understand what you're getting at. If I'm correct, you're saying that it's not enough that all three eyepieces are parfocal, but they have to be parfocal at exactly 160mm? I didn't think the tube length was that critical - I thought it only influenced magnification? So if you used, say, a tube length of 180mm everything would be fine but you'd just get a relatively higher magnification i.e. (180/160)x = 1.125x = 40x1.125 = 45x for a nominal 40x objective? It's difficult to check a standard 10x EP in my modified trinocular tube which has been changed to hold an 1.25" astro EP. What I can do is put a standard 10x EP in the microscope EP holder, focus, then adjust the trinocular astro EP to be parfocal by eye (as best as I can!). Would that be sufficient? If not, I'll have to re-engineer things a bit :)

Thanks

Louise
When you're using a 4x or 10x objective on a bellows, you can do just that: change the extension (tube length) to change magnification. Image quality will deteriorate a bit, but at such low NAs it usually holds up pretty well if you stay within a few cm.

At NA 0.85, it's a whole different situation. You really can't be off by much at all.

When you say "put a standard 10x EP in the microscope EP holder", do you mean in one of the regular eyepiece tube that is used for viewing? (I am not sure what type of head you have - a trinocular with two viewing tubes and one phototube?). Or do you have different heads for viewing and photographing?

Anyway, I would do what you said. Put a regular eyepiece in a place where a regular eyepiece should go. Focus on a subject. Change to the eyepiece you want to use for your afocal setup. Look through the eyepiece with your eye. Do not move the focus wheel! Instead, move the eyepiece it up or down until the same feature is in focus when you look through it. There's your intermediate image plane. Remove your eye and place a camera lens focused at infinity where your eye was.

Edit: and do this with a 10x objective. Counterintuitively, the depth of focus at the intermediate image plane is shallower with low magnification objectives, so you'll be able to find the location of the intermediate image with higher precision with a 10x. But the consequences of being off is greater with the 40x 0.85.

LouiseScot
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Re: Swift Achromat vs Nikon Fluor

#17 Post by LouiseScot » Sat Mar 27, 2021 3:09 pm

viktor j nilsson wrote:
Sat Mar 27, 2021 2:49 pm
LouiseScot wrote: Ah, I think I'm beginning to understand what you're getting at. If I'm correct, you're saying that it's not enough that all three eyepieces are parfocal, but they have to be parfocal at exactly 160mm? I didn't think the tube length was that critical - I thought it only influenced magnification? So if you used, say, a tube length of 180mm everything would be fine but you'd just get a relatively higher magnification i.e. (180/160)x = 1.125x = 40x1.125 = 45x for a nominal 40x objective? It's difficult to check a standard 10x EP in my modified trinocular tube which has been changed to hold an 1.25" astro EP. What I can do is put a standard 10x EP in the microscope EP holder, focus, then adjust the trinocular astro EP to be parfocal by eye (as best as I can!). Would that be sufficient? If not, I'll have to re-engineer things a bit :)

Thanks

Louise
When you're using a 4x or 10x objective on a bellows, you can do just that: change the extension (tube length) to change magnification. Image quality will deteriorate a bit, but at such low NAs it usually holds up pretty well if you stay within a few cm.

At NA 0.85, it's a whole different situation. You really can't be off by much at all.

When you say "put a standard 10x EP in the microscope EP holder", do you mean in one of the regular eyepiece tube that is used for viewing? (I am not sure what type of head you have - a trinocular with two viewing tubes and one phototube?). Or do you have different heads for viewing and photographing?

Anyway, I would do what you said. Put a regular eyepiece in a place where a regular eyepiece should go. Focus on a subject. Change to the eyepiece you want to use for your afocal setup. Look through the eyepiece with your eye. Do not move the focus wheel! Instead, move the eyepiece it up or down until the same feature is in focus when you look through it. There's your intermediate image plane. Remove your eye and place a camera lens focused at infinity where your eye was.

Edit: and do this with a 10x objective. Counterintuitively, the depth of focus at the intermediate image plane is shallower with low magnification objectives, so you'll be able to find the location of the intermediate image with higher precision with a 10x. But the consequences of being off is greater with the 40x 0.85.
Hi again, Viktor

Yes, I can put a standard Swift 10x EP in the Swift EP tube. Astro EP in the modified trinocular tube and height adjusted (not focus adjusted!) to be in focus with the viewing EP. With both in focus I can't see any difference in the image as seen by eye (except the trinocular is much brighter). I'll then need to check that the viewing astro EPs fitted to the Swift EP tubes are still in focus. If not, I'll have to re-engineer their adapters but it's not a big deal to do that.
Anyway, I'll post results when I get them.
Many thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#18 Post by LouiseScot » Mon Mar 29, 2021 3:13 pm

Well, try as I might, I couldn't seem to improve the Pleurosigma images. I did my best to make the trinocular pathway parfocal to the Swift eyepieces. I can't say I could discern any improvement with the Nikon Fluor. I moved onto the Mediterranean diatom slide and also compared images between those taken by my Canon1100d afocally via the trinocular tube, and images taken with a Toupcam eyepiece camera. They may actually be slightly better but it could just be the smaller pixels rather then just being via the eyepiece path. There are so many bits that could influence image quality!

Anyway, here is trinocular Swift 40x vs Nikon Fluor 40x:

Swift_40x_Med_1420_crop100pc.jpg
Swift_40x_Med_1420_crop100pc.jpg (60.78 KiB) Viewed 1232 times
Nikon_40x_Med_1419Crop87.jpg
Nikon_40x_Med_1419Crop87.jpg (60.99 KiB) Viewed 1232 times



And Toupcam Swift 40x vs the Nikon Fluor 40x:

Swift_40x_Med_ToupCrop65pc.jpg
Swift_40x_Med_ToupCrop65pc.jpg (49.35 KiB) Viewed 1232 times
Med_Nikon_40xToupCrop69pc.jpg
Med_Nikon_40xToupCrop69pc.jpg (57.37 KiB) Viewed 1232 times


There are variations with the slight contrast/brightness adjustments I made, but, hopefully, they shouldn't make a big difference. I adjusted the Nikon collar either side of 0.17 but it seemed best at 0.17. I did my best to get the focus the same between objectives and cameras but my judgement and eyesight aren't great...

I look forward to any comments/suggestions :)

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#19 Post by Hobbyst46 » Mon Mar 29, 2021 3:45 pm

To me, in each of the two comparisons, the Nikon objective yields a better image.
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Re: Swift Achromat vs Nikon Fluor

#20 Post by LouiseScot » Mon Mar 29, 2021 3:53 pm

Hobbyst46 wrote:
Mon Mar 29, 2021 3:45 pm
To me, in each of the two comparisons, the Nikon objective yields a better image.
Well I'd like to think so! But I'm not sure the images are quite as good as I hoped for... Maybe I expect too much? The current Canon EFS 18-55mm lens I'm using for the afocal may not be good enough though I'm not sure how much camera lenses contribute to the image quality. I just bought a Canon 50mm f1.8 but I've yet to try it. The Swift stand also has some lenses in it and which might have a bearing.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#21 Post by apochronaut » Mon Mar 29, 2021 4:09 pm

I think you should put a micrometer on the slide and see just how thick the sample/cover slip complex is. Many older slides were made for demonstration or educational use and they made them thick so they could sustain abuse. A .65 objective would still work as well with them as a .65 objective could but a .85 fluorite could easily be degraded enough to not seem that much better than a .65. They were never intended to be used with a .85 fluorite objective. The slide might be as thick as .22 or even thicker. I've seen some really nice slides be as thick as .30. A .85 objective wouldn't even focus on them.

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Re: Swift Achromat vs Nikon Fluor

#22 Post by LouiseScot » Mon Mar 29, 2021 4:35 pm

apochronaut wrote:
Mon Mar 29, 2021 4:09 pm
I think you should put a micrometer on the slide and see just how thick the sample/cover slip complex is. Many older slides were made for demonstration or educational use and they made them thick so they could sustain abuse. A .65 objective would still work as well with them as a .65 objective could but a .85 fluorite could easily be degraded enough to not seem that much better than a .65. They were never intended to be used with a .85 fluorite objective. The slide might be as thick as .22 or even thicker. I've seen some really nice slides be as thick as .30. A .85 objective wouldn't even focus on them.
Today's images just above are from a contemporary slide. The previous vintage slides seem to work best with the collar set to .17 anyway but the slide itself may be thicker than normal. I really only used the vintage slide because it has the Pleurosigma formosa. I Measured the thickness of the slide itself with a digital caliper and it gives 1.85mm compared to 1.1mm for one of my blank slides. I can't really measure just the vintage coverslip thickness because of the mountant. As you say, it may well be thicker than normal but I'm not certain. I'll, er, focus on comparing with contemporary slides :)

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

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Re: Swift Achromat vs Nikon Fluor

#23 Post by apochronaut » Mon Mar 29, 2021 5:55 pm

Of course you can measure the cover slip/sample thickness. You measure the total and subtract the slide.

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Re: Swift Achromat vs Nikon Fluor

#24 Post by LouiseScot » Mon Mar 29, 2021 6:27 pm

apochronaut wrote:
Mon Mar 29, 2021 5:55 pm
Of course you can measure the cover slip/sample thickness. You measure the total and subtract the slide.
Yes, but the difference will be the sample + coverslip so I can't know the coverslip thickness alone. The total is 2.2 and the difference is 0.35mm.

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

apochronaut
Posts: 4221
Joined: Fri May 15, 2015 12:15 am

Re: Swift Achromat vs Nikon Fluor

#25 Post by apochronaut » Mon Mar 29, 2021 8:27 pm

The cover slip thickness recommendation is intended to include the sample thickness. If you use a .17 coverslip, you need a very thin sample such as a smear. For thicker samples you would reduce the thickness of your cover slip. That's why you mic. and grade your cover slips if you have not purchased sized and graded ones. That way with experience you can choose an appropriate thickness cover slip in order to keep your sample thickness within spec. Purchase #1 and 1 1/2. It doesn't matter as much with dry achromat objectives up to .65 N.A. but if you want the kind of imaging from higher N.A. objectives that they are capable of, then the cover slip/sample specification needs to be attended to with some precision.
You are basically trying to test an objective using a sample thickness of twice what the objective was intended to be used for.

LouiseScot
Posts: 558
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: Swift Achromat vs Nikon Fluor

#26 Post by LouiseScot » Mon Mar 29, 2021 8:52 pm

apochronaut wrote:
Mon Mar 29, 2021 8:27 pm
The cover slip thickness recommendation is intended to include the sample thickness. If you use a .17 coverslip, you need a very thin sample such as a smear. For thicker samples you would reduce the thickness of your cover slip. That's why you mic. and grade your cover slips if you have not purchased sized and graded ones. That way with experience you can choose an appropriate thickness cover slip in order to keep your sample thickness within spec. Purchase #1 and 1 1/2. It doesn't matter as much with dry achromat objectives up to .65 N.A. but if you want the kind of imaging from higher N.A. objectives that they are capable of, then the cover slip/sample specification needs to be attended to with some precision.
You are basically trying to test an objective using a sample thickness of twice what the objective was intended to be used for.
Ah, I didn't realise that the sample thickness needs to be added to the coverslip thickness! Of course, I've never had such a high NA dry objective before so these finer points are all new to me. I only have common coverslips and have never had to consider alternatives before either. I don't know where to buy different ones in the UK. I'll just stick to contemporary prepared slides for the critical stuff!

Many thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

apochronaut
Posts: 4221
Joined: Fri May 15, 2015 12:15 am

Re: Swift Achromat vs Nikon Fluor

#27 Post by apochronaut » Tue Mar 30, 2021 1:52 am

There is no guarantee that contemporary prepared slides are not thick either. If you are using higher N.A. objectives and are expecting to be able to interpret the results , you need to be sure of your sample thickness.

Buy a cheap micrometer on ebay and mic. your cover slips, then organize them in their containers , thickest first, separated by pieces of paper or tissue with the thickness marked on it for the covers below.
# 1 covers will be as thin as .12 and as thick as .16 #1 1/2 will be .15 to possibly .18. For most fresh aqueous samples I start with a .12 or .13 if there is a lot of debris. .14 if not. .17 is only useful if the sample is very uncomplicated , even and easy to make a thin sample.

LouiseScot
Posts: 558
Joined: Tue Jul 07, 2020 1:51 pm
Location: Scotland

Re: Swift Achromat vs Nikon Fluor

#28 Post by LouiseScot » Tue Mar 30, 2021 2:10 am

apochronaut wrote:
Tue Mar 30, 2021 1:52 am
There is no guarantee that contemporary prepared slides are not thick either. If you are using higher N.A. objectives and are expecting to be able to interpret the results , you need to be sure of your sample thickness.

Buy a cheap micrometer on ebay and mic. your cover slips, then organize them in their containers , thickest first, separated by pieces of paper or tissue with the thickness marked on it for the covers below.
# 1 covers will be as thin as .12 and as thick as .16 #1 1/2 will be .15 to possibly .18. For most fresh aqueous samples I start with a .12 or .13 if there is a lot of debris. .14 if not. .17 is only useful if the sample is very uncomplicated , even and easy to make a thin sample.
Hi again

The two contemporary diatom slides I have both use 0.17 coverslips and their sample thicknesses are not significant. The digital calipers I have, have a resolution of 0.01mm with an accuracy of +/- 0.02mm so they will probably do for taking measurements. I don't have any different grades of coverslips - only the nominal 0.17 ones. As I mentioned, I don't even know where to buy different grades of coverslips in the UK. I can always switch to 100x oil if there's any doubt. I'm sure, with experience, I'll learn how best to handle the fluor :)

Thanks

Louise
A Nikon CF plan 20x; A Swift 380T; A DIY infinity corrected focus rail system with a 40x/0.65 Olympus Plan, a 10x/0.30 Amscope Plan Fluor, and a 20x/0.75 Nikon Plan Apo

Scarodactyl
Posts: 1350
Joined: Sat Mar 03, 2018 9:09 pm

Re: Swift Achromat vs Nikon Fluor

#29 Post by Scarodactyl » Tue Mar 30, 2021 4:40 am

To me the improvement in color correction looks pretty dramatic, and definitely makes for much nicer photos. I suppose that suggests the swift system is neither non-correcting or at least weakly correcting, at least on CA.

Hobbyst46
Posts: 3416
Joined: Mon Aug 21, 2017 9:02 pm

Re: Swift Achromat vs Nikon Fluor

#30 Post by Hobbyst46 » Tue Mar 30, 2021 5:34 am

I find it fairly difficult to achieve affordable perfect diatom slides that conform with the specifications of the optics.

Affordable slides and coverslips are less expensive than research-grade ones by an order of magnitude. I buy the cheap stuff from China.

Very thin coverslips are more fragile, both during the preparation and afterwards. I use #1.5 coverslips.

When mounting diatoms in resin, it is difficult to achieve a very thin layer of the resin. Too little resin, and air bubbles form. Too much resin, and the coverslip shatters or is blown off by the bubbling resin (during the mounting heating).

The diatoms are initially attached to the coverslip rather than the slide, before the resin is added and heated. Hence, ideally, if during the mounting heating they stayed attached, the thickness of the sample (not counting the slide) is practically the thickness of the coverslip, plus the thickness of the diatom itself.

It just happens that most of my high NA objectives are marked 160/- so coverslip thickness is not an issue - maybe. Still, all that said - it might be tempting to try and mount on the thinnest possible coverslips. Lets see...
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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