On 10/11/2025 at 2:48 PM, CaolIla said:

  On 10/11/2025 at 2:33 PM, Luko said:

  On 10/11/2025 at 1:13 PM, CaolIla said:

The idea is putting some reduction in the tube and why not some extension with lens in it.
BUT there is a BUT with a lens when the distance is the focus length the light is like a donut because the tube of the retra a circular.
I need to but a diffusor on the retra side...

More than a diffusor that you need but rather a fresnel lens of something equivalent, the problem without any converging lens is that all the power will be lost. (That's what happens with the crappy Scubalamp snoot which is only equiped with a diffusor device, used it on one trip, never again, back to Retra snoot now) .This is why the Retra snoot is for me the most efficient one : you see for instance there is a sweet spot according to the distance you aim at your subject, the "halo" of the snoot will get sharper whenever you're on the ideal distance.

Diffusor or fresnel lens it is more or less the same... I'm using a fresnel on my other snoot.

Hi @Luko

I made a test to explain the donut

No lens no difusor only a small output

14 hours ago, CaolIla said:

No lens no difusor only a small output

Disclaimer : I am replying to you but am afraid that we are completely out of the OP topic, sorry for that.

So far I can notice you have 2 problems : one is the black hole inside the light which I guess is the signature of the circular bulb, the other one is that you have a light "fall off" spilling outside of the snoot hole (the outer ring of subdued light around the main light).

For me, it's due to the absence of a condenser lens that would both diffuse the circular light into a flat light and make the light converge to a focus point this avoiding spill off. We (my guide and myself) usually take continuous torch lights when we do macro, that we use when I need precise lighting other than the main snoot light or when two snooted lights are needed.

All of these small torches are equiped first with a lens like this one https://www.uwcamerastore.com/weefine-optical-collector-with-m52-for-smart-focus-6000?gad_source=1&gad_campaignid=21961101493&gbraid=0AAAAAD6tS_h9daR4-OxoqiVVd9_zdO1Lf&gclid=CjwKCAjwr8LHBhBKEiwAy47uUpyg-mpCh6yNn1-WSBCsL9CNJP9mI_UhLEkk2WRtWjKc90Kuc_xbshoCXKoQAvD_BwE

then screwed onto the condenser a plain metallic black funnel to reduce the light spot. However it wouldn't work without the condenser, which is the most important piece.

Just to show you the difference, I snapped 4 images of my mousepad with a tirch light, the condenser and a funnel.

A= full mousepad image lit by the torchlight, B= condenser on, the beam is reduced and condensed, C= condenser and funnel on, exactly what you expect from a snoot, even though I was not aiming at the sweet spot distance, not much light loss, same distance as withe condenser only D= funnel but NO condenser, I had to put the light much closer because of the loss of light, light spills outside of the main focus point, you cannot clearly see it but when I put the light close there are distinctly patterns of the LED light inside the main focus point.

@Luko


With a torchlight it is easy to visualize the result... and it is easy to achieve the goal: have a small spot

It works also good with the LED in the center of the Retra strobes... but a flash from the circular light is not as easier.

1) the need of a longer tube is necessary

2) a lens /fresnel or a concentrator as you name it is important to concentrate the light

3) with a lens with circular or only a LED you will have good "picture" of the light sources when you are at the focal length... that is the main problem. With a circular flash light you will have a bright disk with the dark center.

I made several test "Difussor" with frosted glas or such glasses

I made folowing construct
Light/strobe -> Diffussor --> 1 or more lenses with different focal --> tube with special internal shape to avoid the parasite reflexion --> and why not a lens for a last light concentration

It is not easy to make a compact solution I still exploring in different direction.
Target: Light, easy to (re)build, compact and not expensive.

In the tube a try with good results this shape

important printed with a black mat filament to avoid a maximum of the reflexion and have a nice boundery beetween the black and white zone on the picture.

Small update of my test.

The idea is to have a snoot where the water can go in --> no problems with water coming in ... it is build for that.
Perhaps in an other step I'll try to have air in the snoot but it is not the subject now

The bottom part will be "fix" and the top can be print again and again to try different size length and/or diameter of the opening in the top.

It is also possible to try different type of glas, lens, fresnel to test the result

In the midle it is possible to insert some additional lense to focus the light an put some part in to avoid the reflexion.

Edited 23 hours ago23 hr by CaolIla

a first picture 

You see, no you don't see the donut... I reach the target.

It is not with the "big aperture" but I hold a small cap with a small hole of 9 mm

The idea is to make some cap with different hole size and change it during the dive, Probably printed in TPU

Edited 23 hours ago23 hr by CaolIla

Did you use a fresnel lens?

23 minutes ago, Davide DB said:

Did you use a fresnel lens?

no in this example only a matte glass (like you can find on the Retra snoot.

I have some fresnel lenses from different diameter and focal length. I will probably combine different lenses.

My ultime idea, (result of my precedent test) is to have a part I can put on the top of more or less this solution, with a diaphragme in it.

Why on the end of the snoot... because if the diaphragme is on the begining to much light is lost. I I can focus a maximum of light on a small point (in my case with the smal diaphragme I have from Aliexpress, 25 mm diameter)

The hole will be possible to be adjust from 2 on 25 mm and that with a maximum of power light comming out.

2mm is probaly not usefull but will be possible. (if the guide is good and understand what the photograph want... why not. but this no the scope of the model I show you today

Have you tried this snoot in water? I did similar snoot with couple glasses and didn't seal the tube to allow water coming in, even with support by GPT to setup the right focal length with multiple glasses to reduce the light output angle, it could be only 8mm spot at 10cm distance from the snoot, considering the impact of sea water. Everything looks perfect in the air but when I tried it in the real dive, it didn't work as expected, the spot is much bigger and the brightness was also much more lower as what I tested in air.

@flowdesign

Thanks for your remark. Yes I know under water it is different.
That is exactly the reason I want to optimize the light coming out of the strobe.
My past experience wasn't like I imagined it...
I want to have near 100% of the light output from the strobe coming out on the top.

This time I'll make a "lowtec" snoot (I haven't enough time to do a complex solution.)
I change the design of this snoot.. but at the end I want to seal it to have air in it.

After the coming trip I'll make changes to adapt this solution and I'll make some dive with a modified version of it. (if i'm happy of the base design)

It is allways the same problem not enough time to test before the trip.

a point more is to have a light snoot for travelling I'm at the limite... with the weight.


a big problem I had in the past was the sealing of the lenses to avoiding water coming in the snoot. I'm planing to test some construction without silicon sealing but with TPU

I also want to be able to open it and close it again and again to make some changes in the parts in the snoot.

Change lenses, focal length also type of lense.
Add some fresnel or normal lenses ..

When I found the good combination (the one I like) I'll build a lighter snoot optimized for the lens combination/position/number I chose