Distance between the sensor and Raynox for the best quality

Adalbert · Post by **Adalbert** » Tue Oct 23, 2018 8:29 am

Hello everybody,

As far as I can see the results of the tests show that the lenses from Raynox perform better as the tube lenses if the length of the tube is shorter then the standard one (focused to the infinity).

e.g. at 144mm the DCR-150 with the Mitu M Plan Apo 5x is quite as good as the ITL200 and in the corner even better! Robert gave 9.6 points!
https://www.closeuphotography.com/tube-lens-test

Does anybody know the best distances between the Raynox 150/250 and the sensor for the Mitutoyo (5, 7.5, 10, 20, 50) ?

Thank you in advance.
BR, ADi

Macro_Cosmos · Post by **Macro_Cosmos** » Thu Oct 25, 2018 7:45 am

Distance between the raynox tube lens and objective?
Reversed, as close as possible.

Robert quotes 50mm for non-reversed. I can't recommend for or against that. I don't use a Raynox myself.

Adalbert · Post by **Adalbert** » Thu Oct 25, 2018 8:59 am

Hi Macro_Cosmos,
Thank you for the hint!
This was a typo, of course (I have just corrected :-)
I would like to know the distance between the sensor and the tube lens.
The Raynox DCR-150 has reached the best results at 144mm, better than at 200mm (focused to infinity).
BR, ADi

RobertOToole · Post by **RobertOToole** » Sun Oct 28, 2018 3:24 pm

Hi Adi,

I just posted some results for the 10x M Plan with the Raynox but I have to admit that I did not note the sensor to subject distances with the Raynox 125

http://www.photomacrography.net/forum/v ... hp?t=38363

I promise to take better notes next time I have one on the test setup.

Robert

Macro_Cosmos · Post by **Macro_Cosmos** » Mon Oct 29, 2018 2:23 am

About 204mm if reversed.
Reversed means the text is upside down with respect to the camera.

Don't know about ordinary mounting.

It's simple, just find a distance subject to focus on, put the lens on a bellows or variable tube of some kind. Total extension required = extension length+camera's flange distance.

ChrisR · Post by **ChrisR** » Mon Oct 29, 2018 4:59 am

IS IT that simple?

I realise I'm not clear.
Sure some lenses are asymmetric, or a bit "telephoto" so to focus at infinity, the distance from the sensor will alter when you reverse them.

We'd expect "infinite" optics to work best when focused an infinity, but it ain't necessarily so. In some cases we could be adjusting to minimise aberrations.

I'm not sure if some combination tests have reported non-infinity focusing, working best.

Adalbert · Post by **Adalbert** » Mon Oct 29, 2018 8:36 am

Hi Robert,
I would like to ask you what is the most important advantage of the pushing down of the Mitty 10x ? And, is it better to use a TL with a shorter focal length or to use the normal TL but with the shorter length of the tube (TL<->sensor)?
BR, ADi

Adalbert · Post by **Adalbert** » Mon Oct 29, 2018 8:40 am

Hi Macro_Cosmos,

About 204mm if reversed.

This is the standard distance for the TL focused to the infinity.
The last Robert’s test of the tube-lenses shows that DCR-150 manages CA better at 144mm.
BR, ADi

Adalbert · Post by **Adalbert** » Mon Oct 29, 2018 8:42 am

Hi Chris,
Yes, pushing down is not simple :-)
BR, ADi

RobertOToole · Post by **RobertOToole** » Mon Oct 29, 2018 9:58 am

Adalbert wrote:Hi Robert,
I would like to ask you what is the most important advantage of the pushing down of the Mitty 10x ? And, is it better to use a TL with a shorter focal length or to use the normal TL but with the shorter length of the tube (TL<->sensor)?
BR, ADi

The Mitutoyo 10x image was just about perfect with the ITL200 at 10x. I should post the full size image and share it, its really good looking from edge to edge. So with the 10x pushing down was not 100% as good.

Honestly I don't push down lenses other than for testing but when I was working on that big tube lens test the image quality of the ITL200 with short focus on the Mity 5x really surprised me. It looked better to my eye than the infinity focus image. That makes me think about using lenses pushed down for my own shooting in the future.

The question is of course is the IQ better really? I tried to find out and its very close but I still think pushing down looks slightly better than a 200 FL image re-sized to match.

Hope this answers your question.

Robert

Macro_Cosmos · Post by **Macro_Cosmos** » Mon Oct 29, 2018 10:07 am

ChrisR wrote:IS IT that simple?

I realise I'm not clear.
Sure some lenses are asymmetric, or a bit "telephoto" so to focus at infinity, the distance from the sensor will alter when you reverse them.

We'd expect "infinite" optics to work best when focused an infinity, but it ain't necessarily so. In some cases we could be adjusting to minimise aberrations.

I'm not sure if some combination tests have reported non-infinity focusing, working best.

I think I was way too inconcise with the wording, I was in a rush to do some other things; I will reword it:

The DCR-150 is effectively a 208mm lens.

About 204mm from sensor to the DCR-150 for focus to infinity, if it is to be reversed.

I don't know about ordinary mounting as I've only used mine reversed once, but finding infinity is simple. Simply put the lens on some sort of variable extension device such as a bellows, and find a far object to focus on. Turn on live view and adjust the extension to a sweetspot.

The above method gives infinity focus, which sometimes isn't optimal to minimise aberrations. The extension can be varied to produce different magnifications.

The most common method to mount the Raynox is by using extension tubes. M42 and 58mm types are commonly available on the market. Please note that flocking is essential to minimise annoying stray light. I usually roll up some telescope flocking material and simply insert it into the tubes rather than sticking it on, making it almost permanent.

Adalbert · Post by **Adalbert** » Mon Oct 29, 2018 10:34 am

Hello Robert,
OK, there is no general, simple rule defining the relationship between the TL and CA.
CA depends on the combination of the microscope-lens, focal length of the TL, length of the tube, distance between the TL and the microscope-lens and finally on the quality of the TL :-)
BR, ADi