Latest revision as of 12:18, 10 May 2017

If you're looking for a watch for ultramarathons lasting for 20 to 30 hours, the Epson SF-510 is worth serious consideration. For everyone else it's best avoided as there's little to like about the SF-510. The Epson range feels like it's 5-10 years behind other companies which with the rapid advances we've seen in ergonomics and functionality is an age. The Epson looks rather clunky, with cheap feeling materials and a design that does not seem to have had a lot of effort. If the SF-510 were ultra-budget, it might be more viable, but they'd need to drop the price down much further to be value for money. (Update: the prices have dropped a long way now, so it's looking a little better.) Looking at the four basic questions I use to evaluate the foundational capabilities of a running watch, you can see the weaknesses.

• How far did I run? This is the most basic question, and Epson make a big deal about their "highly accurate GPS tracking." Epson created their own chipset to ensure accuracy, but my testing indicates that the SF-510 is one of the least accurate devices I've tested, even worse than the Epson SF-810. This is a major disappointment given how far behind the state-of-the-art Epson are in other areas. However, if you compare the accuracy of the SF-510 with other watches in extended battery mode, where they wake up and check the GPS signal periodically, then the SF-510 does much better.
• How fast am I running? Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Because GPS never really provides the level of accuracy you need for good pace information, the best watches support the display of current Pace From A Footpod while getting all other data from GPS. Sadly, the Epson does not have this feature, and doesn't even support the use of a Footpod at all.
• Where am I? The SF-510 has no navigation capabilities.
• What's my cadence? Cadence is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. The SF-510 has an internal accelerometer and will display cadence, but there is no option for a Footpod. Typically an internal accelerometer doesn't do a great job, and the SF-510 seems superficially rather poor. Unfortunately, it is not possible to get the Cadence data out in a format that can be analyzed for accuracy, so I can't be sure how bad this is. (For some reason, Epson call Cadence "pitch" which is a little unusual and slightly confusing.)

The only bright spot in an otherwise dismal device is the SF-510's battery life, which I tested at 30 hours, almost exactly what Epson claim. I think this makes it a worthy contender for your money if you need a watch that will give more than 24 hours of running without recharging and without crippling the GPS accuracy. See Watches for Ultrarunning for more details.

Please support this site This review was made possible by readers like you buying products via my links. I buy all the products I review through normal retail channels, which allows me to create unbiased reviews free from the influence of reciprocity, or the need to keep vendors happy. It also ensures I don't get "reviewer specials" that are better than the retail versions.

1 Epson SF-510 Pros

• The biggest advantage of the SF-510 is its long battery life, lasting for 30 hours. This is a chunk longer than other devices can provide with their GPS fully on. Other devices can go even longer, but they have to keep their GPS off most of the time, which can produce vastly inaccurate results.
• The SF-510 is fairly small and looks like a normal watch. Admittedly, that's a normal watch from the 1980s, but that's better than looking like a wrist mounted dive computer. I found the strap to be comfortable and easy to use, something I wish was true for more running watches.
• The SF-510 can support a Bluetooth Heart Rate Monitor. Normally this wouldn't be noted as a pro for a watch, but the Epson SF-810 lacks this support, so it's more the absence of a con than a pro.

2 Epson SF-510 Cons

• The GPS Accuracy is terrible; I'll add more details soon, but for now I'll just say that it's at the bottom of my GPS accuracy table.
• There's no support for a Footpod to give a more accurate Cadence. Of course, that also means no support for displaying your current Pace From A Footpod. The Cadence that is provided is from the internal accelerometer which does not seem great.
• The display is old-school LCD, which is a mixed blessing. It's rather low resolution, and not as nice as a new color display, but it's easier to read without needing a backlight.
• The charging dock for the SF-510 is enormous and would make challenging the watch on the run impractical even if it was supported. However, even if you are prepared to shove the watch, charging dock, and USB battery in your backpack it wouldn't work. Plugging the watch into its docking station terminates any activity.
• The smart phone to feels rather like something from a small startup rather than a major corporation. There is no ongoing communication, so you have to explicitly go through the watch menus to put the watch into Bluetooth listening mode. Using the app is a test of patience and reminds me of the days of recording computer programs on audio tape (a grim memory at best).
• It's theoretically possible to load a satellite pre-cache into the SF-510 for faster satellite acquisition. Unfortunately, this is rather impractical as you have to mess around connecting the watch to your smartphone via Bluetooth, updating the satellite pre-cache, which is then only valid for a few hours. You can't upload the pre-cache via the computer link either. Without the pre-cache, the time to lock onto the satellite signal is painfully long. This is made worse by relatively poor sensitivity; most modern Garmin watches will get a lock inside my house, but the Epson needs a clear view of the sky.
• The SF-510 can upload your workouts via a Bluetooth link to your smart phone, but yet again this proves rather impractical. The Bluetooth link takes so long to upload your workouts that this is unworkable for regular use. The upload via a PC is less painful, but still feels rather crude and unfinished.
• Epson will upload your workouts to their website, which is rather rudimentary. There are various options for syncing your data with other sites, but if you want to have your lap splits included then things get tricky. I had to sync my Epson data with Strava, download CSV data from Epson, download TCX data from a Strava, and then write code to combine the two. You can consider me thoroughly unimpressed.

3 GPS Accuracy

My previous test of the SF-810 was rather grim, so I didn't expect much from the SF-510. Imagine my surprise when the SF-510 managed to disappoint me in spite of rock bottom expectations! I would have thought that the SF-810 and SF-510 would have the same GPS system, but maybe it's tweaked in the SF-510 for greater battery life. The image below is from a small section of the trail I use for testing as I've found it highlights the strengths and weakness of the different devices nicely. In this case, it's just highlighting weaknesses:

• The blue lap markers are widely scattered, and are so bad it's not obvious where they are supposed to be. If you compare with the Suunto Ambit2 image below you can see that the markers are vaguely clustered either side of the true lap, almost like they're avoiding the correct spot.
• The section under the bridge shows some issues with occasional trouble re-acquiring the satellite lock, but like most devices, the SF-510 does better here than in other sections. This is most likely because this is a fairly straight section of trail so even if the satellite signal is lost there's not much overall error introduced. Even here the SF-510 does worse than most devices.
• In the twisty section in the middle the SF-510 does really badly, rarely recording a track that's close to the true distance, and often wandering off aimlessly.
• The sharp corner at the right side is a little better, and this also is common. Most watches nail this surprisingly well, but not the SF-510.

A diagram of the Epson SF-510's tracks, color coded with green indicating good accuracy through to red indicating poor accuracy, and the lap markers as blue dots.

For comparison, here's the tracks from the Suunto Ambit2, which does remarkably well. This is how the data should look.

(I've contacted Epson support and they are aware of the problem.)

4 What's Missing

While I don't consider these missing features as 'cons', it's worth understanding the features that are missing compared with other watches. You'll notice that the SF-510 has a rather long list of missing features.

• Altimeter. GPS is far less accurate vertically than horizontally, so a barometric altimeter can provide a much better idea of your ascent and descent. It can also be useful for navigation if you're ascending or descending a mountain. In some races I've been far more interested in how much ascent is left rather than the distance to the top.
• Extended battery life. Some watches can extend the battery life by turning the GPS reception off for short periods. This can dramatically reduce GPS accuracy, but it's a useful trade-off for some ultramarathons.
• WiFi Uploads. While the automatic upload of workouts via WiFi is nice, the upload will typically only go to the manufacturer's web site.
• Running Dynamics. Some of the newer Garmin watches support Running Dynamics that can show and record Vertical Oscillation (VO) and Ground Contact Time (GCT).
• Apps. I come to really appreciate the extensibility of the newer Garmin watches, and their ability to run custom applications. Suunto has a much simpler version of this capability, which is still better than nothing.
• Activity tracker. While I'm not convinced by the accuracy of most activity tracker's, they are a nice feature and can give additional motivation to keep moving.
• Smartphone Notifications. Having alerts like incoming calls or text messages on your watch is a rather nice, though far from a core feature of a running watch.
• Alerts. Some watches will alert you when a metric is out of range. The alert for Cadence is really useful and one of my favorite features on other watches. Of course, you need a decent measurement of cadence for this to be relevant.

5 Visual Comparison

Epson SF-510 top	Epson SF-510 side	Garmin 235 top	Garmin 235 side	Garmin 225 top	Garmin 225 side
Garmin 620 top	Garmin 620 side	Suunto Ambit3 top	Suunto Ambit3 side	Suunto Ambit2 top	Suunto Ambit2 side
Polar V800 top	Polar V800 side	Garmin Epix top	Garmin Epix side	Leikr 1 top	Leikr 1 side

6 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

1. The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..
2. How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.
3. The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.
4. The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.
5. I give 1-2 bonus points for application support, 1-2 bonus points for data upload, 1-2 bonus points for Optical Heart Rate Monitoring, and 0-1 bonus points for battery life.
6. Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.

6.1 Score Breakdown without a Footpod

6.2 Score Breakdown with a Standard Footpod

6.3 Score Breakdown with a Stryd Footpod

6.4 Basic Features

7 Navigation Features

For "navigation":

• Color Maps gives you full color maps, rather like a smart phone, with roads and paths marked out.
• Track Outline is a display of where you've run, rather like a breadcrumb trail. If there are maps, the outline is superimposed otherwise this is just the outline on its own without any context.
• Course Outline is an outline of a route that can be downloaded. I've found this useful during ultras or in unfamiliar cities where I've needed to know where to go.
• Back To Start is a simple arrow point to your starting point, so it won't help you backtrack.
• Back To Waypoint returns you to a previously marked location using a simple arrow to point.
• Compass. A magnetic compass can help you orient yourself or the map. Without a magnetic compass you have to be moving for the GPS to give you a sense of direction.

(Older Reviews: Polar RC3 GPS, Soleus 1.0, Motorola Motoactv.)