JML 21mm and lighting

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 4:31 am

Hello to all,
I need your help please:

I took a JML 21mm and I'm starting to use it on my set for macro but the first results are unsatisfactory!

What's wrong?

I have a Pentax K5 (CMOS 16MP), a rail controlled by SW and 4 LEDs for lighting
thanks for any suggestions!
Roberto

The setup

the image withe JML21mm

another picture made only for test with the same system but with another lens ... the result is much better ...

ChrisR · Post by **ChrisR** » Mon Oct 14, 2013 5:32 am

Hi Roberto
Out of curiosity, what was the "other lens".

A common problem comes with those conical adapters. From the manufacturer, they're often quite shiny inside.

Assemble everything as you did, including the lights, and remove the camera. Look up the tube/bellows to see if you can see any reflections in there.
If you do, you have found the problem!

Solutions which can work:

use a flat adapter
line the inside of the cone with nonreflective material
cut a mat black disc with critically sized hole, to fit at the camera end of the adapter.

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 5:55 am

Hello Chris,
many thanks for the reply!

yes! I had already thought to internal reflections but there are none, for safety I put a perforated disc of black card, but did not improve anything!

the second photo is made with Vivitar 55mm and tubes

ChrisR · Post by **ChrisR** » Mon Oct 14, 2013 6:37 am

Do the individual frames in the stack all look similar? I mean to each other, and the output?

Have you used the lens successfully before?

Is it possible that a lot of light "spilled" into the front of the lens? Did the paper tube really go a long way behind the subject?

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 6:57 am

the JML is the first time you use it, this lens is always spoken very well ...
I could not believe my eyes after seeing the result.

I tried both with the paper tube long and one just short, but more or less always the same problem

it is better that I do conical?

rjlittlefield · Post by **rjlittlefield** » Mon Oct 14, 2013 7:29 am

ChrisR wrote:Do the individual frames in the stack all look similar? I mean to each other, and the output?

Be sure to check your individual frames as ChrisR suggested.

If the individual frames appear OK (high contrast details), then your problem may be in the stacking.

An effect like this occurs rarely when
1) the first or last frame in a stack is very out-of-focus and therefore low contrast, and
2) the software is set to do brightness correction.
What happens is that the software may choose that very low contrast image to use as a master, then it adjusts all the other images to have similarly low contrast.

If you are using Zerene Stacker, try running the stack again with Options > Preferences > Alignment > Brightness not selected.

--Rik

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 7:56 am

rjlittlefield wrote:
ChrisR wrote:Do the individual frames in the stack all look similar? I mean to each other, and the output?
Be sure to check your individual frames as ChrisR suggested.

If the individual frames appear OK (high contrast details), then your problem may be in the stacking.

.....

--Rik

this part is not clear to me, if you want the individual frames are OK before the stack with the SW?

individual shots already have this problem, there is something that escapes me and I think it resulted in lighting and / or parasitic light

for this was wondering if there is a special system for this lens

ChrisR · Post by **ChrisR** » Mon Oct 14, 2013 8:14 am

Do you have it the right way round? AS far as I can remember there isn't really an indication.
Groove nearest the sensor?

I'm still favouring internal reflections...

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 8:34 am

yes!! the direction is right ...

http://www.photomacrography.net/forum/v ... php?t=9597

rjlittlefield · Post by **rjlittlefield** » Mon Oct 14, 2013 10:42 am

ChrisR wrote:I'm still favouring internal reflections...

I agree.

My copy of the lens can give some reflections from one retaining ring at the back of the lens.

Try cutting a mask of black paper that fits inside the lens barrel, very close to the back surface of the glass.

--Rik

bert01980 · Post by **bert01980** » Mon Oct 14, 2013 11:56 pm

Hello to all,

good news ...
I solved by making the diffuser cone (see attachment) and things have improved a lot,
the test was done quickly without pretensions, but already you can see the improvements ...

I tried to cover the entire inside of the paper with matte black but does not improve the situation much ... Now I just have to find the right balance ...

thank you all for the precious help ...

P.S. but if there are other suggestions I would be happy to receive
Roberto

Pau · Post by **Pau** » Tue Oct 15, 2013 4:06 am

bert01980 wrote: P.S. but if there are other suggestions I would be happy to receive

If the issue -as its seems from your last post- is reflection on the front lens, a small light hood would effectively surpress that reflection. You can make it with a cilinder of black matte material

bert01980 · Post by **bert01980** » Tue Oct 15, 2013 7:42 am

Pau wrote:
bert01980 wrote: P.S. but if there are other suggestions I would be happy to receive
If the issue -as its seems from your last post- is reflection on the front lens, a small light hood would effectively surpress that reflection. You can make it with a cilinder of black matte material

Hi Pau,
thanks for the help!!!

like this:

Pau · Post by **Pau** » Tue Oct 15, 2013 10:46 am

Yes, but in order to not interfere with subjet illumination and to cut as less as possible the working distance a shorter and narrower one would be better (although a bit more difficult to make and mount)
I've cut the conic lens end because mine and all other JML 21mm I've seen are flat endend.

(if you don't want your image reworked please let me know and I'll remove it)

bert01980 · Post by **bert01980** » Tue Oct 15, 2013 12:19 pm

Hello Pau, Thanks again for the help ...
I figured it was better to smaller, Today and tomorrow are away for work but as soon as I try and I'll know ...