Tube Lens Test Final Results

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Lou Jost
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Post by Lou Jost »

Adalbert, yes, it is good to focus on one magnification at a time, but it is also important to realize that there is nothing special about 200mm except that this is the tube focal length that gives the rated magnification. Since you are also already considering other magnifications, I just want to remind you that there are other (possibly better) ways to get sharper corners. Note that using a longer focal length does not take the objective away from its designed optimum, whereas as Rik says, changing the infinity design point can cause problems. Robert has shown that sometimes it works fine, but in cases that haven't been tested, nothing is certain. On the other hand, if the corners are bad and the center is sharp, using a slightly longer focal length is virtually guaranteed to sharpen the corners.

Edit: Of course this will also slightly reduce the overall sharpness; you'll need to experiment to see what balance you want to reach in your application.
Last edited by Lou Jost on Wed Oct 24, 2018 12:05 pm, edited 1 time in total.

RobertOToole
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Post by RobertOToole »

Adalbert wrote:Hi Robert,

Your test: https://www.closeuphotography.com/tube-lens-test under: “Tube Lenses shorter than 200mm
Thorlabs ITL200
https://www.closeuphotography.com/thorlabs-itl200/
Set-up:
• Short focus, 144 mm extension from sensor to lens
• Reverse mount
• 75mm from tube lens to objective
Image Quality:
• Overall: 9.6 out of 10
• Center: 8.5
• Corner: 8.5
• Chromatic Aberration Control: 10
.
.
.

RAYNOX 208MM (43mm x 0.50 mount)

Also know as: DCR-150, Macroscopic Lens Model M-150, Model CM-2000 1.5X, +4.8 diopter

Closeuphotography.com/raynox-tube-lens
Set-up:
• Short focus, 144 mm extension from sensor to lens
• Normal mount
• 50mm extenstion from tube lens to objective
Image Quality:
• Overall: 9.6 out of 10
• Center: 9.5
• Corner: 10
• Chromatic Aberration Control: 9.5
So, at 144mm is the quality in the corner for Raynox = 10 and for ITL200 = 8.5.
Independent of the typo at ITL, Raynox has achieved the full 10 points in any case.
The image quality in the corner is very important for me, therefore I’m asking for that :-)

BR, ADi
Yes, you are correct.

I don't know how Raynox did those designs. As closeup filters they are ok but as a tube lens they are just about impossible to beat in IQ.

RobertOToole
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Post by RobertOToole »

Also in my recent post about my findings with the Mitutoyo 10x M Plan,

http://www.photomacrography.net/forum/v ... hp?t=38289

Short focus did not improve image quality with the ITL200 but thankfully with infinity and in reverse mount the ITL200 performance was excellent.

FYI, I'm finishing up the 10x test now over the next couple of days. The results are very interesting so far :o

Robert

Adalbert
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Post by Adalbert »

Hi Robert,
I’ m looking forward to seeing the results of your test (and comparing them with my assumption)!
So, if I had to guess I would say for the TL focused to the infinity first the ITL200,
then the DCR-150 and for the shorter length of the tube the both on the same place :-)
DCR-150 is really not bad and a good and cheap alternative to the ITL200.
I’m reassembling my Harley rail.
BR, ADi

JohnyM
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Post by JohnyM »

Great test Robert, thank you for doing that

Sorry for digging up, but i just now started to think about making univerasal tube lens system (no bellows) and sticking to ~100mm tube would make it really eazy for me.

Could this phenomenon that Robert discovered be explained by this:

1) Tube lens like Raynox is heavily stopped down by microscope objective. So it's not responding to extension change as much as to be expected.
2) Shorter tube lenses are less stopped down, so they do not respond to this "short focusing" as well as longer ones.
3) Since path between objective and lens is no longer 00 , changing distance between objective and lens serves as spherical abberation compensation. And could possibly serve to introduce "cover glass" correction.
4) Perceived improvement is result of larger effective aperture?
5) This result is possible due to moderate objective aperture and will not carry to higher NA objectives, and will eventually bring worse results, unless distance between tube lens and objective will be "nailed". Eventually (with increasing NA and decreasing extension) that "nailed" spot will be inside the tube lens or past it.

Sadly, due to 3,4,5 this is not a good solution for a system with multiple objectives and single tube lens?

Offtopic:
Anyone tested Raynox 250 +1.7 TC vs Raynox 150? Robert :D ?

Georg
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Tubes

Post by Georg »

Hey Robert
May I ask u which extensions u use for the raynox 150 setup? For both settings
This should also work fine with a full frame camera?
Will use a sony A7R4
Thanks for your help

Lou Jost
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Post by Lou Jost »

I've founmd in my tube lens tests that best full frame settings are not generally the same as best APS settings, and that was true of the Raynox. The arrangement that gave the best central sharpness also gave worse FF corners. That arrangement would look like the best arrangement on APS, but on FF it was worthwhile to sacrifice a bit of central sharpness to get decent corners.

Georg
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Post by Georg »

Lou Jost wrote:I've founmd in my tube lens tests that best full frame settings are not generally the same as best APS settings, and that was true of the Raynox. The arrangement that gave the best central sharpness also gave worse FF corners. That arrangement would look like the best arrangement on APS, but on FF it was worthwhile to sacrifice a bit of central sharpness to get decent corners.
You‘re right Lou

The more I‘m doing my research for the best system to use the mitus on FF the more I get confused ... Dozens of ways to mount and tweak every combination of tubes extensions ...
I will go for the 200mm/180mm camera lens and in front the mitu
And the bellows raynox 150/250 system - think the bellow is quite useful in stepping down the magnification and otherwise I can also revers the raynox lenses to step down...

This forum is really useful but can make u crazy in the next second :D

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