Min/Max Focal Dist w/+10 Diopter

[SeahorseDeb]

Does anyone know what the minimum/maximum focal distance is using the Backscatter +10 diopter? I'm trying to get a minimum focal distance of roughly 8 inches. I understand I may need to stack them, but their specifications don't state. Also, any specs on the glass? At $19.95 I'm thinking that could be questionable. Thankyou!!

---------- Post added April 10th, 2014 at 11:10 PM ----------

NVM, found my own answer... 6-12"....

 

[EL Pistoffo]

Sometimes the min may not be 6". It depends on the quality of the diopter. With generic lenses, I could get maybe 7"-8". The max with a +10 can actually be a lot more than 12".

 

[SeahorseDeb]

Sometimes the min may not be 6". It depends on the quality of the diopter. With generic lenses, I could get maybe 7"-8". The max with a +10 can actually be a lot more than 12".

Thanks for commenting, every little bit helps! I use a tray, not a tripod, so finding stability to film a critter with a lens that has a 6" or less focal distance isn't a smart purchase for me. Lake algea isn't the most interesting thing to video either, even if it is static. 12" is reasonable for me, now where's that Ling Cod on a nest of eggs......

 

[EL Pistoffo]

When I tested my diopters in the pool I found that my +10 had a min of about 7"-8" and a max of about 2' or 3'. An easy way to test a diopter under water for the min focal distance (and max if using stronger diopters) is to fill an adequately sized container with water and submerge your GoPro and a ruler. Use something as a subject like a toy or whatever and move the camera back and forth over the ruler slowly, then watch the video. It will give you a ballpark idea of what your looking for.

 

[Interceptor121]

This sounds like the +10 diopter is not really +10 in water

Usually a +10 in water will have a 100mm focal lenght and working distance around 4 inches or 10 cm.

Something at 7 inches looks more like a +6 in water?!?

 

[EL Pistoffo]

This sounds like the +10 diopter is not really +10 in water

Usually a +10 in water will have a 100mm focal lenght and working distance around 4 inches or 10 cm.

Something at 7 inches looks more like a +6 in water?!?

Apparently that's what happens when your dealing with cheap diopters intended for land use. That's what is popularly used with GoPros. To get to within 4 inches you'd need to stack 3 of them.

I watched a YouTube video of a SubSee +5 or +10 tested with a GoPro in a pool. They were able easily get within just a few inches of the subject. You get what you pay for.

 

[SeahorseDeb]

When I tested my diopters in the pool I found that my +10 had a min of about 7"-8" and a max of about 2' or 3'. An easy way to test a diopter under water for the min focal distance (and max if using stronger diopters) is to fill an adequately sized container with water and submerge your GoPro and a ruler. Use something as a subject like a toy or whatever and move the camera back and forth over the ruler slowly, then watch the video. It will give you a ballpark idea of what your looking for.

Does the particulate matter from cloudy lakes and the green water/low visibility further reduce the power of the diopter or am I correct in thinking that when I'm only a foot away it isn't going to have an effect? Thank you!!!

---------- Post added April 11th, 2014 at 07:17 PM ----------

Usually a +10 in water will have a 100mm focal lenght and working distance around 4 inches or 10 cm

Okay, maybe I am getting a handle on the mathematics of the diopters....therefore what you're teaching is that this means that a +10 equals 10cm of focal distance? And then if I add more +10's I'm dividing in half the length if each lens behind it, so 2 of the +10 diopters stacked would be 10cm/-1/2=5cm?

 

[EL Pistoffo]

Does the particulate matter from cloudy lakes and the green water/low visibility further reduce the power of the diopter or am I correct in thinking that when I'm only a foot away it isn't going to have an effect? Thank you!!!

The particulate won't have any different effect on the diopter as it would with any other lens or bare port. Cloudy water will reduce visibility naturally but wont reduce the power of the diopter. These diopters have very little magnification effect UW as opposed to on land. What they in essence provide UW is the ability to get closer to your subject will remaining in focus. With a +10 if you are anywhere in between 24" to 8" of your subject, it will be in focus. The GoPro with a bare port can come as close as 12" to the subject and retain focus.

What helps a great deal in giving you a much closer effect when using a diopter paired with a GoPro is setting the camera to Narrow FOV. It enlarges the image, coupled with a closer proximity to the subject, resulting in a more macro looking image.

All this is what I have gathered in my experience using diopters with GoPros.

 

[SeahorseDeb]

Thank you El Pistoffo.....I'm getting closer to understanding how these lenses work in water. In the past, I was occasionally tempted to photograph a subject, only to find out I'm too close. That being in my past, and I'm no longer doing photography due to my limited access to critters, I turned to video. I know I'm going to be in a situation where I will want to attempt a close up video, hence the reason for all my questions. Your Blue Herron Bridge video is a good example of filling the frame with a close up, I liked it and seeing the GoPro's potential of good control coupled with good subject matter. In still photography there's the challenge for me to hold still and capture that moment, in video I've got a few seconds but I need to understand the optics. I'll attach a macro shot here, I was trying to capture the crossed eye look of the Buffalo Sculpins eyes,...I didn't quite get it; Puget Sound with Canon G-9, no filters used. Thanks for your experience and advice!

 

[Interceptor121]

Okay, maybe I am getting a handle on the mathematics of the diopters....therefore what you're teaching is that this means that a +10 equals 10cm of focal distance? And then if I add more +10's I'm dividing in half the length if each lens behind it, so 2 of the +10 diopters stacked would be 10cm/-1/2=5cm?

Pretty much

100/Diopter power= focal length this is in a way related to the working distance but not exactly the same

Close up lens for underwater use made of two elements glass with sealed air space have very little variation in water

For example an Inon UCL-165 is 7.37 in air and 6.06 in water

Single lens diopters will drop significantly in water to half or less of the power so 10 becomes 5 focal length 200mm or 8"