For performance testing, I have been using the K57 for a few days including writing this review. I have been using a mechanical keyboard in some shape or form for the last 12 years so jumping back to a membrane keyboard was immediately noticeable. Thankfully the K57 using a mostly standard layout with the exception of the bottom row which has a shorter spacebar and larger control keys for some reason. Because of that adjusting over to the K57 went smoothly. Limiting the function layer to just the three connection options helps for simplicity as well. Now I do wish the media controls had a few things different. I would prefer a knob for the volume control like Corsair typically does. I would also like all of the media controls to be backlit like the rest of the keyboard. They may not see the same use as the rest of the keyboard, but being able to see them in low light, especially with all of the buttons having the same shape and size, lighting would make them easier to use.
So I mentioned that the membrane keyboard was noticeably different from the mechanical keyboards I’m used to using. There are two main fundamental differences. For starters, membrane keyboards activate at the bottom of their throw where a mechanical switch activates in the middle, so that does take some adjustment. But I do still bottom out my keys either way so it wasn’t too big of a difference. The main difference for me is just in the key feel. Keypresses are heavier and get heavier as you push the key down. There is a little bit of feedback, but it isn’t as smooth as a mechanical switch.
Wireless performance is always a concern but in my testing Corsair’s Slipstream tech did a great job at keeping latency low. In fact, in all the time I have been using the keyboard I hadn’t ever run into a situation where I could tell it was wireless at all. The range wasn’t an issue, even when I tested the keyboard across the room from my PC. The BlueTooth performance was similar as well. In fact, having the wireless dongle and then two Bluetooth options might be one of the best features of the K57. You can program it to three devices and hot-swap between them by holding the function key and pressing F5-F7. If you plan on using the K57 at your desk this might not be as useful, but in the living room, it did work with our Android TV based Shield TV, VR PC, and Xbox One. PS4 isn’t supported though.
So the backlighting and wireless battery life are tied to together. It also depends on if you use the wireless dongle or Bluetooth. You can expect a little better battery life when using Bluetooth, but this is because of the higher polling rate that Slipstream offers. So without lighting being turned on at all Corsair says you should expect 175 hours on a charge with Slipstream or 200 hours on Bluetooth. Turning the lighting on a medium brightness cuts that down significantly to 35 hours on slipstream and 40 hours on Bluetooth. That does, however, mean that you could potentially get close to a full work week on one charge if you only use it during work with the lighting on. For comparison Corsairs K63 which doesn’t use their new LEDs has a battery life of 25 hours with the lighting turned on low, not a standard lighting brightness.
As for the lighting itself, the membrane design which I would consider a downside for overall performance does have a big benefit with a backplate that is fully transparent. This allows the glow around each key to be more prominent. Unlike old school membrane keyboards with RGB lighting the K57 has fully individual LEDs, so each key has its own LED allowing for the same effects and customizability that mechanical keyboards have. All of the key legends are well lit and when you turn the lighting up to the brightest setting I would actually say that it is too bright. The medium setting that they did the battery tests on is what I would recommend for brightness unless you really want your entire desk area to glow. Lighting effects are smooth with no stuttering or issues as well.