Glasseye Snapper

This one is from the same general area (right side of Marsa Shagra bay) and again less than 2m depth. I have only seen it inside tube holes and it strongly reminds me of the Caribbean tube blennies in behavior and head shape. I haven't come across anything like it for the Red Sea or general Pacific area.

 

Bart

 

 RhinocerosBlenny1.JPG   96.36K   7 downloads

 

 RhinocerosBlenny2.JPG   73.99K   6 downloads

This one was found in less than 2m depth on an algae-covered limestone slab in the midst of a sandy bay (near boat docking site of Marsa Shagra dive camp). It somewhat resembles a rockskipper but I can't find any images in books or fishbase with such pronounced "rabbit ears". Any ideas?

 

Bart

 

 RabbitBlenny1.JPG   172.14K   6 downloads

 

 RabbitBlenny2.JPG   64.64K   5 downloads

This image was taken on a night dive with the intended subject being a Cook's cardinalfish (cropped out to highlight the 2-3cm fish of interest here). I only now, two years later, spotted this pale goby-like fish but was puzzled by its wedge-shaped head. I have only seen that in jawfish but according to my book (Lieske & Meyers) there is only one jawfish in the Red Sea, the blotched jawfish (Stalix davidsheni), and it is listed as Gulf of Aqaba only while the image is from the Marsa Alam area. Is there an alternative ID or is a juvenile jawfish the only one with this head shape.

 

Bart

 

 TentativeJawfish.JPG   70.14K   6 downloads

A little while ago I asked about GoPro file sizes to judge how much memory is needed to record all dives on a trip in their entirety. I couldn't find any real numbers online so when my GoPro hero 3 black came in yesterday I decided to do the experiment for most formats and frame rates. The somewhat surprising results are listed below.

 

format frame rate fov time (sec) size (MB) size/hr(GB) sizeM (MB) size/hr(GB)

720   60 w 60 150   9.0    0.0    0.0

720 120 w 60 226 13.6 1288  77.3  

960   48 w 60 224 13.4    0.0    0.0

960 100 w 60 224 13.4    0.0    0.0

1080 24 w 60 221 13.3   501  30.1  

1080 30 w 60 149   8.9    0.0    0.0

1080 48 w 60 223 13.4   582  34.9  

1080 60 w 78 289 13.3 1416  65.4  

1080 30 m 60 149   8.9    0.0    0.0

1080 30 n 60 149    8.9    0.0    0.0

1440 24 w 60 223 13.4   599  35.9  

1440 30 w 60 224 13.4   742  44.5  

1440 48 w 60 223 13.4 1148  68.9  

1524 30 w 60 334 20.0    0.0    0.0 2.7K

2160 15 w 60 334 20.0    0.0    0.0 4K

1524 24 w 60 334 20.0    0.0    0.0 2.7K cine

2160 12 w 60 334 20.0    0.0    0.0 4K cine

 

Only 3 different file sizes were observed at approximately 9, 13.5, and 20GB/hr. For instance all frame rates at 1920x1440 resolution yield 13.5GB/hr and 1920x1080 at 30 frames/sec actually gave a smaller file than at 24 frames/sec. I can't say I understand this, especially the latter, but it suggests that compression rates are adjusted to make each recording mode fit into one of those three data rates. After I convert the GoPro files to .avi with the GoPro software the file sizes do start to become different and in line with expectations based on resolution and frame rate (last column, but I didn't convert all of them and on first try the 2.7K and 4K modes didn't want to convert at all).

 

The good news is that my intended 1080p @ 30frames/sec gives the smallest file and with 9GB/hr even my long shallow dives should fit on the 16GB card I bought. Even the 13.5GB/hr data rate will capture at least most of any typical dive. I also looked at clips using the wide/medium/narrow FOV settings and I thought the quality of all of them looked good (I read somewhere the narrow FOV modes looked poor).

 

I will look at image quality, actual FOV of the narrower modes, and closest focus distance in more detail later but so far I am very impressed. I also got my new Oly OMD EM-5 this weekend so they are fighting for my attention. Lots to read and experiment with before my May 22-June 5 Red Sea trip.

 

I expect to log about 50 dives and some 60hrs under water so the current plan is to get a second 16GB card and a 2TB Western Digitial 2.5" MyBook drive (about 200gram and it is powered through the USB cable). That should give ample space for video records of all dives as long as I keep them in GoPro format. If the winter next year lasts as long as this one I will at least have lots of footage to look at.

 

Bart

 

PS: I got my 16GB Sandisk class 10 micro SD card from "The Source" for just 20 bucks. The normal price was $60 and the camera store tried to sell me a 8GB no-brand card for $25. Seems to be a good deal!

Hi all,

I just checked in to see what people thought about the Metabones "speedbooster", announced with some fanfare a few days ago, and am surprised that it hasn't come up yet. I had for a long time thought this was such an obvious interesting tool that the fact it didn't exist must imply it can't be done. Now apparently it has been done. So why not earlier? There was some suggestion that it can only be done with mirrorless but I don't get that.

Anyway, if you haven't heard about it just check dpreview or google it. It is basically a reverse teleconverter which demagnifies the image. The result is a larger FOV (you no longer need to apply the APS-C crop factor to the focal length) and a gain in apparent aperture.

The first adapter will allow you to use Canon EF lenses for use on Sony APS-C NEX bodies, by applying a 0.71x demagnification, yielding a 1 stop speed gain. A version for m43 olympus and panasonic bodies should come later. These could have up to a 0.5x demagnification and 2 stop light gain. So my cheap but good 35mm F2 would become a 35mm F1 on m43. It don't think you get the shallow depth of field of a true F1 lens but the two stops of light will help negate some of the drawbacks of the smaller m43 sensor under low light.
A potential counter argument for UW use is that without adapter you would use a shorter focal length m43 lens to get the same FOV as a FF lens, and shorter focal length normally translates to closer minimum focus (an UW advantage of m43 that is not often mentioned). But for lenses that can already focus close, like the 35mm F2 or 100mm macro, it should be interesting.

If image quality is not affected, and that is the claim/expectation, then I would be very interested. Both to keep using some of my Canon lenses after a switch to m43 and to see what the extra light can do. The question is, will FF lens diameters fit into mirrorless camera ports?

Bart