Advice on one-way films for studying fish

Tintguy1980 · January 5

14 minutes ago, Fish1 said:

Not sure I understand here - is DR the same as one-way, or something different? And wouldn't it be better to have the VLT as high as possible so the subject can see the groups as well as possible - e.g. 80%? Or is the VLT for 'looking the other way', so we want it as low as possible so we are sure the group can't see the subject?

Balancing act for sure. As long as the dark side is dark enough and the bright side is bright enough your subject will see the group. Then there's the trick of the group not seeing its reflection. I would be surprised, if what you're asking can be achieved using any film greater than 55-60% VLT. Not to mention VLR on the shiny side should be approaching 10 numerical points different than the VLR on the dark side to achieve a good one-way application (Pro opinion). The human eye detects reflectivity at 11-12%. Fish???

All I can say is you may have to do multiple installs on multiple glass and begin with the lighter DR's, which I failed to mention before, come in 40%, 50, possibly 60% VLT. I am unsure where the tech is these days, but I do know that when someone requests an interrogation room setting for security purposes, 30%, 25%, 20%, 15%, 10%, 05% are choices depending on how secure you want to interrupt viewing toward the darkened room.

Bham · January 5

Interested in this scenario but here is my :twocents from the "not so smart" section. I see problems with the enclosures being made of glass. I feel the reflective properties of glass itself combined with the reflective properties of water, both of these combined are going to be a problem with this experiment. I just feel like the multiple pieces of glass that will have to be used are going to create multiple reflection issues. i.e. - the way a fish tank looks at the corners.

Also the fact that film will change the environment much like putting film on a sunroom and killing all the plants in the room. Film is going to change the environmental conditions to where they are incorrect.

Water temp I would think would also be a factor in this experiment and is going to be difficult to get correct without some sort of heat lamp or water heater option. Using light to have one side brighter than the other is going to also hinder keeping the same temp in all areas of the test.

Fish generally group according to size and safety. Size being key because we all know big fish eat little fish so the grouping will need to be very consistent in that aspect. They also use the cover and currents to determine where they feel safest.

All in all I just think this test will be rather inconclusive because of the difficulties of recreating the "proper" situations for said testing and man made tanks with minimal environmental similarities will be the reason for it.

Again, just my two cents.

Tintguy1980 · January 6

On 1/5/2024 at 4:14 PM, Bham said:

Interested in this scenario but here is my from the "not so smart" section. I see problems with the enclosures being made of glass. I feel the reflective properties of glass itself combined with the reflective properties of water, both of these combined are going to be a problem with this experiment. I just feel like the multiple pieces of glass that will have to be used are going to create multiple reflection issues. i.e. - the way a fish tank looks at the corners.

Also the fact that film will change the environment much like putting film on a sunroom and killing all the plants in the room. Film is going to change the environmental conditions to where they are incorrect.

Water temp I would think would also be a factor in this experiment and is going to be difficult to get correct without some sort of heat lamp or water heater option. Using light to have one side brighter than the other is going to also hinder keeping the same temp in all areas of the test.

Fish generally group according to size and safety. Size being key because we all know big fish eat little fish so the grouping will need to be very consistent in that aspect. They also use the cover and currents to determine where they feel safest.

All in all I just think this test will be rather inconclusive because of the difficulties of recreating the "proper" situations for said testing and man made tanks with minimal environmental similarities will be the reason for it.

Again, just my two cents.

You're smarter than you give yourself credit for.

I thought I put a blurb about fish seeing themselves in the tank glass, however, I should have gone into it more so. Thanks for catching it and backing this discussion up. :thumb

Fish1 · January 10

Thanks both of you for your comments - all good points. Will write a longer reply when I get a chance. The fish are just in these tanks for the tests, so we can keep water temperature stable, and we will have artificial plants etc at the backs so that the fish are more comfortable in the space. We'll line the tanks with something non-reflective (we usually use beige shower curtain), and use diffuse light to avoid reflections, so hopefully that will solve the reflection problem, but we'll have to check with a camera in the water or something what it looks like from the fish point of view. Interesting what you say about when human eye can detect reflectivity - no idea what this is for other animals.

Bham · January 10

In my opinion, which of course could be way wrong :heh I don't think fish in general see well at all. Fish in an almost perfectly clear tank is one thing, but fish seeing thru murky, hazy, particle filled water; well that's totally different. Pretty sure we all know sharks smell way better than they see and I would assume it's about the same for say large mouth bass. I just don't think LMB see very well unless it is directly in from of them. Even then, I fell like it is limited distance. As far as stationary floating and looking around goes for bass; Most of the time I think bass are mainly using one eye, sideways; and down is not really in their field of view much at all.