Mirror/Periscope Style Top-Down Photobox

[Rosseau]

If you're reading this I'm sure you're aware of the sometimes dramatic differences in colour and perspective which become visible only from looking down on our tanks.

It can be awkward to work the camera from above for several reasons especially if you have a closed canopy.

-It is difficult to get the camera physically into the space
-It is difficult not to block out light
etc. etc.


Would something like this design work?



Already I forsee some problems with it and I pose a few of questions.

How much, if at all, will the mirror degrade and distort image quality?

Will focusing be too difficult? (I suspect it will not be especially for users of manual focus)

Will the box inherently block out the light of the subject underneat making it useless?
-Depending on the angle of the mirror I suspect this could be overcome, however this may generate distortion.


The box could even have black acrylic which extends partially through the surface of the water to stop surface reflective glare, unwanted noisey light and surficial water distortion caused by water movement.



Thoughts are very much appreciated.

Cheers,

Rosseau

[Rosseau]

I took a few quick shots using a cheap mirror I have laying around.

Focusing was easy.

Image quality appears high.

Distortion of shapes appears minimal to nil (pic of text).

There does however seem to be some sort of double reflection going on (look at the outside edges of the key). This may be due to the fact that most mirrors effectively have 2 reflecting surfaces? Changing the angles used may negate this?... hmm...






Bonus to anyone who reads the text

Ideas?

[Phyl]

...phytoplankton communities...

You're going to want to flatten the water surface in order to eliminate the ripple effect on the water surface, which is why most folks use a topdown box set in the surface of the water to take pictures from above. The mirror idea is interesting. The need to brace the camera to achieve a decent depth of field is one of the reasons that I haven't quite gotten that technique down yet.

Interesting approach though!

[jwedehase]

Shot in the dark:

Population Dynamics of Harmful Cyanobacteria - Jef Huisman and Florence D. Hulot

This looks like a potentially viable option. I'd imagine the light blockage would be even less than having the entire camera up there.

[Rosseau]

It's actually from my biological limnology textbook. Limnology:Lake and River Ecosystems. R.G. Wetzel. (exciting huh?) I have an exam in a few hours. It's amazing how much what I learn in school and in this hobby are somewhat interchangable.


I think that this will work and am going to go ahead and build something along these lines when I have a chance.

I may try to mount the mirror with the ability to adjust its pitch.

Also, there will be "baffles" (I'm not sure what to call them) that will extend from the mirror down into the water.

Does anybody know if the mirrors in our SLR's are anything special? I ask because I'm wondering about this double reflection seen in the key pic.

Thanks for the responses.

[BeanAnimal]

You will need a first surface front coated optical mirror. Try Edmund Scientific. That will prevent the double reflection and also improve your effective fstop compared to a back coated mirror.

[BeanAnimal]

As also mentioned you will need a "lens" on the end of the watertight extension so that the periscope can be partially submerged. The interior of the periscope should be flat black.

http://www.edmundoptics.com/onlineca...productID=1906

[BeanAnimal]

These are high quality mirrors... what you will need.
http://www.anchoroptics.com/catalog/product.cfm?id=286
http://www.anchoroptics.com/catalog/product.cfm?id=272

These are cheap mirrors and will likely show distortion but are MUCH cheaper and may be something to start with.
http://www.firstsurfacemirrors.com/
http://www.fsmirrors.com/