RAYNOX DCR 250 and 150

pedroalves · Post by **pedroalves** » Tue Jan 23, 2018 1:15 pm

Hello all,

as many of you (i guess) i'm using the Raynox DCR 250 as a tube lens.
For the 250, i'm working with a distance of 125 mm between the camera sensor and the raynox.
A friend of mine is using a different distance, achieved moving the raynox naked (without the microscope objective) from the camera until 'he can focus on the building across the street'. Thus focused on infinity.

My question
- is that a good practice or do we must use the standard distance for the raynox, i.e. 125 mm ?

Many thanks in advance.

Pedro

rjlittlefield · Post by **rjlittlefield** » Tue Jan 23, 2018 1:22 pm

Your friend's approach is more correct.

If you measure 125 mm, that should be with reference to a special point inside the lens, called the "image principal plane" or "rear principal plane". Unfortunately that special point is not marked on the lens or specified in any of the literature. The simplest way to find it is to focus at infinity, then measure from the sensor!

--Rik

pedroalves · Post by **pedroalves** » Tue Jan 23, 2018 1:39 pm

Thanks Rik,

that's what i thought, reason why i post the question here.
I don't know how much 10 mm (more or less) can affect the image quality.
Right now i'm using a Sony A7rII, with the DCR 250 (maybe the 150 is more suitable for FF camera??) and i'm not happy with the image quality (astigmatism it seems).

P.S. i forgot to mention that i'm using the raynox reversed, dunno if this changes anything.

Cheers,
Pedro

jojm · Post by **jojm** » Tue Jan 23, 2018 2:49 pm

Salut Pedro, content de te voir ici.

Please could you tell us what did decide you to change your camera to Sony A7RII from yours OM-D EM5 Mk II.
Your results seem very good to my eyes and I'm curious to understand what pushed you to move.

pedroalves · Post by **pedroalves** » Tue Jan 23, 2018 3:01 pm

Bonsoir Jean-Marc,

thank you very much for the compliment, coming from someone like you, it's something very special.
However, i must admit that i'm not happy with my results. I started micro photography about 2 years ago, so i have a world ahead of me to discover.
I cannot compare my photos with those od people who have been engaged in photography for years, decades.

I still keep my Olympus (a good camera, underappreciated in my hands), the Sony experience appears in an attempt to improve the definition and resolution of images. A better look overall.
For now i'm disappointed, the differences are not evident.

In my humble opinion, my problem (i mean, what I really have to improve) it is the field of lighting. Also the post processing.

I'm just trying to understand if/what i'm doing wrong.

If someone is curious about my pictures, take a look here:

https://www.mindat.org/user-13063.html

Thanks again both.

Pedro

ChrisR · Post by **ChrisR** » Tue Jan 23, 2018 5:26 pm

Olá Pedro
Yes, you would expect to have problems of coverage, with a full frame camera with a "tube" lens that short. I can't find what objective you're using, but bear in mind that many struggle to cover APS, at rated magnification. They cover less with reduced magnification.
I expect the biggest benefit you'd see from the Sony sensor would be a wider dynamic range. Maybe be a lower noise floor at base iso.
I also can't see anything wrong with your images! I wish we had minerals like those in the UK

rjlittlefield · Post by **rjlittlefield** » Tue Jan 23, 2018 7:29 pm

pedroalves wrote: i forgot to mention that i'm using the raynox reversed, dunno if this changes anything.

Not really. Reversed, the reference is to the lens's other principal plane. (It has two.) Other than that, all the same.

--Rik

pedroalves · Post by **pedroalves** » Wed Jan 24, 2018 1:44 pm

Hello Rik, Chris,

thank you both for the clarifications.

Chris, UK is full of pretty minerals, much more than Portugal

Cheers,
P.