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I taught my annual Digital Master class in Key Largo last week, and having six days of local diving provided a bit of time to test new gear. One item of significance was the new Sigma 20mm F-1.4 prime wide angle. I shot it on a Canon 5Ds, SEACAM housing, Superdome, and 57.5mm port extension. This is the same one I use for my 16-35mm lens. I did not obsess over what port extension would put me in exact nodal point of the lens. Rather, this is simply plug and play with gear I had easily at hand. Here are the results: Sigma 20mm lens on Canon 5D3 for scale Normal perspective of 20mm lens underwater, chosen to illustrate primary subject on same plane of focus as background Test of near focus, with seafan lower left actually touching the Superdome and zone of AF on this portion of seafan screenshot at 100%, corner detail lower right screenshot at 100%, corner detail lower left screenshot at 100%, detail close focus on seafan lower left In that this lens is Sigma, it can work either Nikon or Canon. I find great potential here and bring it to your collective attention due to collective angst over poor corner resolution in many wide angle optics used UW.
GoPro video file sizes
Glasseye Snapper posted a topic in Video Gear and TechniqueA 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!