Glasseye Snapper

Hi Mark,

Regarding point 1, with m43 having half the diagonal length of FF you get the same FOV at the same distance when using half the focal length. So a 90mm macro on FF at its minimum focus distance will give you the same image as the 45mm macro at that same distance. When you only care about FOV then there really is no major difference except for FF having more and larger pixels. Of course with the m43 lens you have the option to go even closer until it reaches its 1:1 imaging point where the frame is filled by an object halve the size of what you can capture with the FF macro lens. Some consider this as a gain of apparent magnification others as a loss of effective FOV (capturing a smaller piece of what's out there). In the end people are taking great macro images with both types of camera and I decided that finding subjects and selecting the shooting/lighting conditions is what matters more than sensor size. 

Bart

Hi Jason,

Apologies for not following up on this thread, you will normally find me in the critter ID and DSLR gear forums. I've been interested in anything living in water, well especially fish, from as long as I can remember. Got into diving in the 80s while a student in the Netherlands but lost touch when graduate studies and then work at the UofA in Canada took over. However, from 2000 on I've been back and got into UW photography around 2003 or so. Edmonton is a nice city but if you ask what is at the top of the list of my dislikes it is that there is no Ocean within driving distance. So the bad news is that it is mostly one 2-week scuba/photography trip a year, the good news is that I am now sitting in the airport and my flight to Europe leaves in 60 minutes. The trip includes 2 weeks of diving in the Red Sea and very much looking forward to it, especially with a bag full of new camera gear to explore.

What is your connection to Cebu/Philippines. I went to Batangas last year and expect that I will be back to that region on a future trip.

Cheers,  Bart

I think I finally found this one on fishbase: Hirculops cornifer

According to fishbase its distribution is "Western Indian Ocean: Red Sea south to Pondoland, South Africa. Likely at Seychelles."

Here is the best matching image from fishbase.

Although the drawing above is a very good match, there are a bunch of images that are very different, some with crest, some without, and some with rather different shape and size of cirri. Not sure if that is sexual or other dimorphism or more than one species is shown on fishbase.

Bart

I had my first stab at mounting the GoPro directly on the Nauticam port for the Olympus 60mm Macro lens. It isn't pretty but it seems quite sturdy and, my main concern, should not interfere with stills photography. I may end up putting the iTorch on a short arm using the housing mounting ball and put a Nano focus light in the hot shoe. I also have the ball-to-GoPro adapter and several other odds and ends to experiment with when I get the system underwater in 10 days, 3hours and 17 minutes from now

Here is the overview image

 GoPro1.JPG   64.02K   3 downloads

And a close-up from the mount point

 GoPro2.JPG   124.97K   3 downloads

The foam is to make the flat GoPro mounting clip that comes with the camera fit the round port barrel. I also image it gives a bit of extra grip compared to hard plastic on aluminum, but perhaps it isn't necessary. It is held in place with cable ties. I tried a hose-clamp first which worked but I realized that it probably isn't made of marine grade steel so would end up a rusty mess.

Bart

I measured the gopro field of view in water it is around 90 degrees diagonal and 80 degrees horizontal out of the standard dive housing. That is equivalent to 22mm focal length. Now when you put a close up lens that has a focal length of 100mm on its own assuming it does not vignette is like shooting with a 22mm equivalent small sensor camera from 10cm away. Things are still tiny as usually at that distance a compact can step to 50mm. What I am saying is that the gopro already gets focus around 8". If you put a lens in front of it you can take it down to 4" and it will probably focus between 4" and 12" but then further away it will be blurred. Am not sure this is worth doing unless you want to use the camera as a POV spycam in a fixed position close to a fish like garden eels or similar

That 22mm is probably the full-frame equivalent value. To get the same FOV for a much smaller sensor the actual, not FF equivalent, lens focal length is much smaller (just like the m43 fish-eye is 8mm whereas the FF fisheye is 15mm). For diopters the ratio of real focal length of lens and diopter is what matters for magnification. For a short focal length lens you would need a very short focal length diopter, preferably approaching the lens focal length. For the GoPro that would leave you with millimeters of working space if you could find a +50 diopter to start with. It will allow you to focus closer than the 8" which can be beneficial in murky water but not being able to focus on any thing beyond the focal length of the diopter is a pain for continuous use. For an 100mm, aka +10 diopter, a point 100mm in front of the diopter is in the focal plane which means it will appear at infinity to the camera lens, so you can't focus beyond that.

Bart