The Tech Zone => Gadgets => Topic started by: RBEmerson on September 30, 2016, 09:03:28 pm

Title: Sena Prism tips?
Post by: RBEmerson on September 30, 2016, 09:03:28 pm
I just pulled the trigger on a Sena Prism found on eBay. I'm presently in Maine (hint: the best damn lobster roll in the known universe comes from Lunch on the Wharf in Corea - Schoodic Penninsula) and the Prism is in the post office back home. So we haven't officially met yet.

I'm looking for "works for me" or "don't even think about..." tips. I'll be pairing the Prism with my 20S, so expect full functionality.

Title: Re: Sena Prism tips?
Post by: RBEmerson on October 09, 2016, 01:34:55 pm
I've been playing with the Prism. Here are two examples - they're ZIP files because YouTube and Dropbox compress video files to save space. Images in their files are miserable. So here's the real deal. Download them to view them. I swear they're virus and malware free. Honest. Short demo ( -  Crossing Chesapeake Bay Bridge. (

I like the HD imagery. Whether the 60 FPS images are better than the Prism's 30 FPS is an open question. IMHO it's a "so what".

The manual sucks. It has two major omissions and a number of "say what?" items.

Omission 1: The manual shows how to open the back of the camera and insert the battery and microSD (32G max according to the manual). But it shows exactly nothing about extracting the battery. There is a small orange tab (or dohicky) that holds the battery in place. There's a black plastic tab on the battery, clearly meant to extract the battery. Except the orange whatsit holds the battery and tab is useless. It turns out the orange whatever must be rotated clockwise, as far as possible, to release battery. Plan on using a small pusher (e.g., unbent paperclip) to shove the orange thingamabob out of the way. Tilt the camera lens up and the battery will probably slide out, at least to the point where the tab can used to pull battery out. Slide a battery back in and the orange twisty thing will pop back into place. Practice this move a lot. The camera eats batteries like popcorn at a movie.

Omission 2: The manual goes on at great length about Bluetooth connections. A lot. Pairing a Sena product (or some non-Sena product) with the camera, via what most people think of as Bluetooth pairing (e.g., pairing with a car, wireless headphones, etc. but not, not, not with a smartphone) appears to work. And it should. Sorta. But BT pairing will not give full control of the Prism. In some instances, the one thing that works - starting and stopping recording - goes away. And doesn't come back. What always works is audio via an intercom mic - as it should.

The solution is not in the manual except for a brief, ambiguous footnote early in Section 10 of the manual. The proper procedure: put the intercom in intercom pairing mode. Put the Prism Set mode - Device settings. Scroll to bluetooth HEADPHONE pairing (their upper & lower case). Click the S button (makes sense when you have a camera to play with) and Prism will go into its hunt for anything that uses Bluetooth technology. Such as an intercom. Once the intercom is satisfied intercom pairing has happened, the Prism will show "Complete". Get out of Set mode and back to Video mode (first option after Set mode). After a short pause you'll hear "Prism connected". Push the jog knob (20S or SMH-10) and you'll hear "recording" - press again and it stops. Yea! Power down the intercom and Prism. Power up the intercom, and then the Prism. Everything still works. Yea! Turn while pressing the jog knob and the Prism scrolls through Single Shot, Burst shots, Time lapse, and back to Video (Set must be done with the camera buttons). Push the intercom's phone button three times and the Prism goes into "Deep Sleep" mode (somewhat like "sleep" on a Mac or PC). Three taps and... wakey wakey. But nowhere does the manual say the bit about pairing with the intercom in "intercom pairing" mode - nowhere.  :crazy:

This mess hinges on semantics. Intercom connections between other intercoms or the Prism use Bluetooth technology. But... pairing with a smartphone or GPS is not done with intercom pairing. Ever. Even though that pairing uses Bluetooth technology, too. The only way to connect an intercom to a smartphone or GPS is with "phone pairing". (See the intercom manual for details) Do a Bluetooth pairing with a smartphone and pairing will happen. And that's it. The phone can't access the Prism, and the Prism won't do anything through the phone. A Sena tech confirmed pairing the Prism with a phone is useless. I do not know what happens with pairing a GPS to the Prism. Maybe the Prism records GPS audio, maybe not. I'll try this sometime.

"Say what?" items are mostly about various mode options. Usually it comes down to does or that option hammer the battery. In some cases it's unclear how (usually mic) options interact, if at all. They don't spell out that if a smartphone is paired to an intercom, with the Prism, it's no longer able to interact with the intercom. No music or GPS when the Prism is powered up and connected to the intercom. There's a reason for this, but it's out of the scope of this review (see the intercom manual for a hint as to why).

Other gripes center on firmware. As with any Sena product's firmware, it can be updated in the field. It requires a Mac or PC (no Linux support) and a USB connection. Well, that's the claim. In the two years the product has been on the market, there has been no update. Not to fix things, not to add or revise functionality. The camera is still FW Ver. Does updating work? Dunno... :shrug:

What works? The jog knob and phone button controls work well and make controlling the camera, while riding, very easy. As I said, the imagery certainly works for me. As the demos show, the intercom mic works well, even if the rider is babbling like an idiot - um, yes, well... Wind noise and motor noise depend on the mic's placement. There is an external mic (which Sena calls an internal mic - more semantics). It's really great for making videos with lots of rushing wind and maybe a little motor noise. Production values, people, production values. Videos with wind noise are annoying and suck!!! Disable the internal/external mic and go with the helmet mic. Please!

The lens field of vision can be set to fisheye or 90 degrees. The resolution can be 1080, 750 (or is it 760?), or four hundred-whatever. Tapping the phone button while recording takes a .JPG frame from the video. I haven't tried burst or time lapse. Yet.

Using a 32G chip... haven't gotten anywhere near filling one yet.

The battery... oohhh, here comes bad news. The claim is 1 hour of recording. 30-45 minutes is probably closer to the truth. In-camera charging takes 3-4 hours (via USB). The best way to beat this is buy Sena's external charger and a spare battery. The charger comes with a battery and has space for two batteries. Buy a battery and you now have have three batteries. The charger is also powered via USB. AFAIK, it's not a "fast" charger. Power can come from a computer, wall wart, or plug-in 12V adapter.

There are two buttons on the camera: mode and "S". Mode shifts through modes (Video, Single Shot, etc.) or options in Set mode. The "S" button (if it has a name, I forget what) is the "do it" button. Push it in any camera mode and something happens. In Set mode. whatever option is shown on the camera happens. The "do it" button.

There is no video playback. Connect a USB cable to the camera (a neat Sena microUSB plug can go through an opening in the back of the camera, or you can open the back and use a not so cool plug) or a microHDMI plug to TV cable. Either that will show playback from the camera.

The screen shows mode icons, setting titles, etc. It informs but doesn't show video. Meh - not really a gripe.

The camera comes with a  bunch of mounts. There are three options for helmet mounts: clamp to the side of the helmet, stick a mount somewhere on the helmet (chin, top, side... you get the idea), or a goggle strap mount. There are two articulated mounts (put the camera on the gas tank, wind screen, saddle bag... on and on). There's a handlebar (or crash bar) mount.

The camera, on its own, is water-resistant. It can get wet, but don't take it swimming. Put it in the included watertight case, use the top buttons (no BT intercom does well swimming or diving), and impress the socks of anyone who likes underwater video.

Bottom line: Yes, I'd buy it again. Intercom control of the camera is very good. Bike helmet mounts are clearly the camera's focus. But... Sena customer communications range between near incomprehensibly and none at all. Call them up and (anything else may be considered racist - save tech support is clearly English as a second language - from other than Spanish). Sena replies on their corporate forums are very rare. Battery use time is, IMHO, too short, charging too long. The manual sucks. But, knowing what I know now, I'd buy the camera again, and be glad of it.

Recommended with the caveats listed above.  :thumbsup:

Title: Re: Sena Prism tips?
Post by: RBEmerson on October 16, 2016, 05:06:40 pm
A while later...

The biggest gripe is aiming the camera. Clamping the ball going into the camera mount socket is a serious PITA. My worry is over-stressing the plastic bits in the mount. See the Shotcut thread for a fix for being tilted off being horizontal. There is no good fix if the camera is point down too low (lots of road and bike) or too high (lots of leaves or sky).

Connecting a 20S to the camera is actually very easy. Too bad the manual doesn't spell out how to do it.

(The manual does explain moving around in the menu options) The best starting point is to clear out the Prism's pairing list. Go to headphone pairing and start headphone pairing. On the 20S, go to intercom pairing. Eventually the Prism and 20S will connect to each other. Power down the 20S and Prism (not needed but this is the more reliable way to go). Power up the 20S and let it get to its idle state. Power up the Prism. It may take 5-15 seconds to announce it's connected to the 20S ("Prism Connected" or something like it). Press the jog dial and turn it to step through the video modes. Press the jog dial for a second and some video event (filming, single shot, burst, time lapse) will happen. Press again to stop recording. Press the phone button three times quickly (blip-blip-blip) and the Prism will drop into sleep mode. Three phone button blips and the Prism wakes up. (The Prism does not power up if it's completely powered down by pressing the top buttons - no intercom connection).

Set mode cannot be accessed by the 20S (or any intercom).

Title: Re: Sena Prism tips?
Post by: RBEmerson on October 25, 2016, 11:24:28 pm
After a few of hours of bike "filming", I still like the Prism. I did one continuous 25 minute run (see my RR on PA 125 - this time with video. And the car from hell blocking the best part of the ride). At the end of the "scene", there was no "your battery is dying" warning. I carried a pair of spare batteries in a USB powered charger. I swapped the batteries before starting up 125. After leaving Shamokin (the north end of 125), I shot a few minutes of video on another stretch of road, again without complaint and with no warning. I still recommend planning to swap batteries fairly frequently if shooting a lot. When I knew I was in a place I wouldn't be shooting, I used the 20S to put the camera into "deep sleep" mode (three taps of the phone button) which means far less draw than in idle-not shooting mode. Another three taps of the phone button and the camera is awake and ready to go. Assume about 15-30 seconds from tap-tap-tap to "ready to shoot". In general, using the 20S (or SMH-10) to control the camera works as expected.

I still can't get the camera exactly vertical. Again it was tilted 2-3 degrees off vertical. And that shows up when running on straight road that disappears off an edge on the road. It's enough to be fairly obvious. This time I stood in front of a mirror, looking at the camera sitting on my helmet. I thought I had the "lean" sorted out. Guess not, huh. Since the camera lens is about even with a horizontal line across my eyes, I first got tilted the camera until I was sighting across the top of the camera, and then tilted the lens up a bit. That worked.

I shot some footage right about sunset two thirds of the shot before sunset, the remaining third at and after sunset. The camera produced a clear, usable image. Oncoming headlights, and very bright taillights produce a "bloom" around the light source. You either mind or don't mind about the effect. However, any CCD sensor will do the same thing.

Again, overall, I like the Prism.

Title: Re: Sena Prism tips?
Post by: RBEmerson on January 07, 2017, 01:38:01 pm
I posted the following on the Sena user forum. I'm interested to see if it lasts.
Quote from: RBEmerson


                  STOP NOW! DO NOT CONTINUE!


For anyone who wants to use a 64 Gb microSD, here's how it's done.

First, the Prism uses FAT32 file system, and that's limited to 32Gb. But...there's a way around that. I've found two programs that will format to almost any desired device or partition size. Once that is done, the Prism will use that device (microSD) without a problem. Sort of.

First, how to format the microSD. This cannot be done using the camera. This must be done on a PC. AFAIK, there is no Mac version of these programs.

I recommend going to

www dot ridgecrop dot demon dot co dot uk forward slash index dot htm question fat32format dot htm

If this makes no sense to you, STOP NOW!

On the first line of the page, where it says Note:, at the end of that line is the word "here", treated as a link. Use it to d/l the GUI version of the formatter. If you're good with cmd, use that version. It's all the same.

Unzip the program into any convenient folder. Connect the microSD. Run the formatter. It will default to 32 Gb, but offer the actual size of the microSD. Pick that, of course. Do a quick format. Using the file explorer of your choice, add the folder DCIM at the root, and 100MEDIA one level down. Use all caps. At the root level, create a file called prism.bin. I used a simple text editor to create an empty file, and renamed it to prism.bin.

Eject the microSD from the PC and put it into the Prism - power off, of course. Power up the Prism. The microSD level icon will show an empty microSD (filled icon) - this is as it should be. Start using the Prism as usual. If done correctly, the control panel will show time advancing (video or time lapse) or increasing file count for single and burst modes. If none of this happens, try reformatting the microSD 32Gb. That works, try the formatter again, doing a slow format (very, very slow - it's 64Gb on an microSD, after all). If the microSD works in your PC, it should be fine in the camera.

Do not format your microSD in the Prism. It can't format a microSD larger than 32 Gb. It won't create 32 Gb partition or anything else. You must format on a PC. Got that?

If you've gotten to this point and are still confused about the above, killed your microSD, or bricked your Prism, don't blame me. I told you to stop if the instructions aren't clear to you. You're on your own, sport.

At the moment I'm doing a time lapse of a snowfall. Works like a charm.

As I said above, if something goes wrong, don't blame me.  :p

Title: Re: Sena Prism tips?
Post by: RBEmerson on January 09, 2017, 12:19:19 pm
The microSD hack continues to work - yea. The external battery? Not so much. The problem is the Prism's USB micro plug/socket. Keeping the plug in place is frustrating, even with the camera on a tripod, doing nothing. I  suspect the connection will be even less cooperative on a bike. I'm trying to think of a way to be certain the plug doesn't wiggle around enough to become a problem. Most likely I'll try running a band (cable tie? Wide rubber band?) around the camera, just below the lens, put a strain relief loop (360deg. loop)in the cable, and hope for the best. There's no need, on the road, to open the camera up for a battery change or microSD change, so there is some hope here...

Title: Re: Sena Prism tips?
Post by: RBEmerson on January 18, 2017, 09:57:16 pm
Lessons learned after a four hour video (not time-lapse) run with a 64G microSD:
  • Multi-hour continuous videos don't happen
  • The camera creates a "chapter" lasting +/- 50 minutes before closing the file and opening a new file
  • The camera takes +/- 30 seconds to cycle from the old chapter to a new chapter
  • A chapter of video takes up about 3.8G
  • If the camera loses power, the chapter in progress will be unreadable
  • Securing a microSD plug in the camera is still a challenge to one's patience

Title: Re: Sena Prism tips?
Post by: RBEmerson on March 12, 2017, 02:58:12 pm
I've resolved the "loose USB cable" issue. The cables supplied by Sena fit into the camera back tightly, as well as making reliable electrical contacts. The cable is too short to reach a battery pack unless a) you have a should pocket and b) the pocket will hold the battery. Plan B is simple: buy a short (1.5 meters seems to be the common "shorty" cable sold by China Inc.) USB extension cord. The male connector on the Sena cable plugs into the extension cord female connector and the male connector goes to the battery pack's female socket. The remaining challenge, keeping the cable from flapping about, is left as an exercise for the student.  :p

This arrangement was worked extremely well for a full day's riding. Admittedly, most of the content is of no enduring interest, but it might just earn its keep as a dashcam. Although it doesn't recirculate after some amount of recording, the 64G capacity isn't filled at the end of the day. After recording a potential discussion with a BMW car trying to push into me, I might just consider the matter further...

Title: Re: Sena Prism tips?
Post by: RBEmerson on March 27, 2017, 09:04:07 pm
The Prism continues to work with the tricked out 64G microSD and external battery pack. Sorta...

Good news: Initially I thought there was a gap between the end of one file and the start of the next when doing hours long rides/video. In fact, there's no discernible break from one file to the next. If you start a curve at the end of file 1, hit the apex, and the camera starts file 2, splice the end and start together and everything's great.

Good/Bad (Bad/Good) news: I discovered I'd lost most of the control of the camera when using my 20S intercom. I rebuilt and repaired BT pairings, updated the 20S firmware, and... no change. Bad news...
At some point it dawned on me that the Prism and 20S use an intercom connection, not a BT sharing of some sort. With headphone pairing (same process a 20S rider would use to talk to another 20S user), the 20S takes over control again. It's in the Prism manual, BTW.

Bad news: 1080 @ 30 fps is proving to be a near waste of time if shooting while moving. The resolution just isn't there, the camera is busy filling parts of scenes, and... with some analysis and experimentation, the problems become obvious. The fix, for now, is to shoot 720 @ 60 fps. Naturally, resolution suffers, but at 60 fps many of the artifacts seen at 1080 @ 30 fps aren't there, which gives a somewhat better result.

Sena hasn't said diddly about a Prism 2.0, the Prism 1.0 becoming 1080 @ 60 fps capable, or even a firmware update. Based on an exchange, earlier today, with a Sena support person, basically nobody knows nothin'. No rumors, no heads-up about a new product, no heads-up about an update.

The camera has a lot of good things going for it at $200 (bare minimum kit with a helmet clamp). The 20S control is good. The ability to turn the camera into start it and forget it. That's all very good. But in the end it's all about the image. Despite claiming to be a 1080 camera, it's really a 720 camera. And I think we all want all the resolution we can get.

I'll keep the camera for now (I have to, given the effort I put into it), but I'll watch the market for a successor without having to drink the GoPro Kool-Aid.

Title: Re: Sena Prism tips?
Post by: RBEmerson on July 20, 2017, 10:53:15 am
Eff it. The case started to come apart. Sena replaced it (took over a month!) but I won't even open the box. 1080p at 30 fps compared to 1080p at 60 fps is simply too lame. I've moved to an SJCam SJ7 that will shoot up to 4K (30 fps - forget canyon carving shot at 30 fps).

Here's a 1080p sample uploaded as a 4K video to keep YouTube compression from making a mess of the video:

If your connection can stand it, view at 4K. Pause and check out the grass on the right side of the road. Much of the time it's almost artifact-free.  :thumbsup: :thumbsup:

Title: Re: Sena Prism tips?
Post by: Daboo on July 20, 2017, 03:30:56 pm
Your feedback is great.  Looks like the replacement camera will work fine for you.  I like how the price isn't outlandish either.

I experienced a similar quandary.  I have a Sena 10C, which is a combination BT and camera.  Not much different in size than the Sena 20S by itself.  I did two trips in the past month.  One down from Seattle to Utah to go through the five national parks there, then another a week and a half later to go to a rally in South Dakota, then back home through Canada.  The Sena 10C when it works, is great.  I hit times though during the trips, where I had to do the paperclip reset several times a day.  My guess is that it has an internal memory error and using it all day long for several days, ends up writing code into that space that makes it get more and more corrupted till it finally won't restart.

I bought the Sena 10C on a bit of a whim.  I wanted a 20S originally and found them on sale a couple years ago.  That's unheard of to find any Sena products on sale.  So I picked up the 10C with the camera.  I had visions of posting my rides on forums...but soon gave that up when I realized the effort to trim out the boring parts was too time and computer intensive to be worthwhile. I read about the 10C on some Sena forums, I found that many people were using them as a "dash" cam.  Except on those trips, that's exactly how I use mine all the time.

When the Sena 10C started acting up, I did some searching online for an alternative.  I ended up coming right back to it in the end.  I want a BT headset to hear the instructions on my GPS, so that's a given and one thing hanging off my helmet.  I've come to like the ability to capture a still photo while shooting the video while riding.  There's times when I see something off to the side, but there isn't a good place to pull over, or the other person I'm riding with may not want to stop either.  I can turn my head and capture that still photo.  It isn't as good of quality as when I use my SLR...but I wouldn't stop if I only had the SLR as an option.  Plus, even if the still shot isn't captured just right, I have the video frames before and after that I can use.

I could buy something like a Contour that is a stand alone camera, but then if mounted on my helmet, I have an extra thing hanging off it.  That just bothers me.  And I really do not like the look of a Go Pro sticking up on top of my helmet.  IMHO, it looks dorky.  No offense meant to anyone on that.  It's just a personal opinion.  If I used a bike mounted camera, that works great...but leaves me without that ability to take video and still shots of things I see on the side of the road that are interesting.

One thing I found that works great for me, and might for you, is to take my videos using the "loop" recording mode.  I set my camera to take 5 minute file sizes.  It's much much easier to edit in that size and you can splice segments together easily that way too.

Here's an example of the still image I can get on the fly.


Not sure how to share video on this forum.

This September, Sena is coming out with an updated Sena 10C.  Upgraded video capabilities, etc.  I may buy one of those for Christmas.


Title: Re: Sena Prism tips?
Post by: RBEmerson on July 21, 2017, 04:50:53 pm
Sena's Prism is generally the best choice for a 20S, SMH10, etc. owner. The voice reports are a win. There are some other details (external power, water resistance w/out the dive case) that are wins, too. I'm ambivalent about the status screen and menu process. While I used to think the lack of at least real time imagery was just whinging, but once it's demonstrated, it's hard to give it up. Playback is less of a priority, mostly immediate gratification (all those happy post-millennials high-fiving and generally acting like they're on some sort of upper).

Where the Prism and 10C utterly fail is the lack of 1080p at 60 fps.

Freeze this video and check out the detail along the side of the road, or freeze at 00:57 and check out the rocks on the right. No detail, just slabs of grey.

With an external power supply (and a little ingenuity to come up with a strain relief to keep the plug in place) and a 64G chip, the Prism will basically cover most of a day's riding. At 30 fps. 720 @ 60 fps is, in some ways, better(!). The DSP (digital signal processor) isn't all that great. Even raw video has problems that show up with a little effort. Enlarge the image to "full screen" on a large screen and it's all too obvious.

In short, nice package, nice BT interface, OK UI on the camera, but the part it's all about, the image, is... fail.

Here's a screen capture from the SJ7. I used VLC to run the video, froze the playback, and captured what was on the screen. Check out the detail in the rock wall, the strata on the side of the mountain, and the power line towers on the ridge. The sky is over-exposed (the clouds in the left center have bleached out). For a $200 camera, that's not too bad.

There really are near suicides that pull off passes like that. It's not uncommon. It's effin' scary to watch. Check out where the car on the right's right tires are.  :eek:

Being a GP clone, it hangs out in the breeze and the mounting arms are quaint. A top mount isn't just visually silly, the POV (point of view) doesn't match what riders see. At least the side mount's POV is quite close. With a little tweaking, the FOV can be almost free of the helmet, giving a better "you are there" experience.

The SJ7 isn't perfect. It'll drown in a heavy dew, and on occasion it freezes up. Unlike the 10C and Prism, there's no way to check the camera while rolling. But most of the time, it gobbles up photons and writes them down, which is what it's all about.

(Embedding YouTube video: start the video, tap sharing, and click on "Embed". Ctl-C / copy the blue stuff in the address window and paste it into your post. You will not see it in Preview. You'll see it when you've posted.)

Title: Re: Sena Prism tips?
Post by: RBEmerson on August 04, 2017, 08:19:29 pm
This about as good a representation of the SJ7, on YouTube, short of access to the raw video. Not too shabby, eh?

Here's the full video, but it wasn't uploaded as 4K (long, boring story about that), so the imagery isn't as good as the sample.

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