I've owned the original A7s before upgrading to the A7sii. The A7s was already one of the most amazing cameras to shoot in low light and the A7sii makes it an even more competent camera with better processing and IBIS.I shot the A7s for photography stills. I understand it's mainly made for a video shooter however I needed something for natural light photos (no flash) in low light. Flash can be amazing if used right, however there is a certain loveliness to natural light photos without artificial light - natural shadows and purposeful darkness can help enhance the moody look of photos that feels genuine. Plus it's not always convenient to walk around several pounds of lighting equipment - off camera flash, flash stand, diffusers, reflectors, etc. For this purpose there's no better camera than the Sony A7s series. I loved my A7s as it could capture photos that other cameras simply weren't capable of capturing. A7s photos had a unique look because they were taken in a situation that no other camera could produce.The A7sii upgrade was an immensely helpful refinement of the original A7s:1. THE SENSOR - the sensor has remained the same. There's no new silicon for image quality capture, but additional image processing sorcery by Sony has made it slightly more competent at low light. Most online reviews and tests agree that noise improved about one stop over the predecessor. So ISO 12800 shots look like ISO 6400 shots which is a great improvement!2. AUTOFOCUS - the autofocus of the A7sii feels slightly snappier and better and finding focus in the dark. The A7s and A7sii are contrast detection focus cameras. While this might seem like a hindrance, my experience with the AF of these cameras is that they do surprisingly well because the camera's low light performance is so good. It would acquire focus in areas to dark for any other camera to acquire focus. The A7sii improves on this with slightly more consistent AF. Again, I think this is due to better processing of the camera rather than a sensor redesign. (AF points are on the sensor itself). Despite the improvements in AF, contrast detection AF does have its limitations. CD AF simply can't do tracking and continuous AF as well as PDAF. While my A7riii and A7iii can do continuous eye AF tracking, the A7sii simply can't continuously track subjects if they move. Using continuous AF gives you a constant jittery AF shake. This has to do with how CDAF works, it needs to move the focus above and past the target AF and measure the best contrast creating "AF shake" and it simply won't work with continuous AF. The A7sii is strictly an AF-S lock -and-recompose camera.3. Speaking of Eye AF, contrary to what many may believe, Eye-AF IS POSSIBLE with this camera. However it does not function like, or is as well refined as the eye AF in the A7r/A7/A9 series. You can do eye AF in AF-S where the camera simply finds the eye and locks focus on it. If the subject moves or if your hands move then the focus is thrown off as you're already locked. You would have to recompose and find the eye again. The behavior is more akin to DSLRs where you press the shutter down at the location of your desired focus, lock, and recompose for proper framing. To combat hand shake or subject movement, you will have to use your body to rock back and forth while burst shooting to ensure you will get a shot with the best focus. It's not as efficient as the newer A7 series but most DSLR shooters will be familiar with this method.4. SHUTTER - the A7sii has a redesigned shutter that feels softer and less violent than the previous gen 1 shutter. The original A7s shutter was never bad but the A7sii is more dampened with less sliding shock which may contribute to camera shake during hand-held shoots. In addition I've read at many review sites that the new shutter mechanism should also prolong the life of the shutter so less shutter replacements in the future.5. BODY AND ERGNOMICS. The body is significantly better than the original A7s body. The gen 1 cameras were very small and slim but were generally barebones. The grip of the gen 1 bodies were often to small and uncomfortable and many complained about comfort. The gen 2 bodies have a wider girth in the grip and is more comfortable to hold. Furthermore there are extra programmable buttons that you can assign to your needs. The body is slightly larger, however it makes the camera seem more like a serious professional camera than a hobby camera. The new magnesium body and matte paint finish is also less prone to chipping like the older gen 1 A7 series and less resistant to the ugly finger oils smudges.6. IBIS. IBIS is by far the best improvement for the A7sii and all of the gen 2 bodies. IBIS was added to the A7ii, A7rii, and A7sii and it is an amazing killer feature. The secret of the A7s's low light shooting is clean ISO noise even at ridiculously high ISOs. However no matter how high your ISO is, shutter speed makes the difference between a grainy high ISO shot and a highly detail rich high ISO shot. The addition of IBIS makes hand held shooting at speeds of 1/30 (usually my limit for handheld) clean and sharp. I can even get handheld shots of 1/15 or slower. The IBIS also have the added benefit for smoother video shooting. Normally video shooters need a gimbal which are normally huge, heavy, and the electronic ones can be quite expensive. While no replacement for a real gimbal, the IBIS makes smooth handheld video shooting a possibility. Used alongside a gimbal or weighted stabilizer, the two systems work together for smooth beautifully stabilized video.7. BATTERY LIFE. Battery life in all of the the A7 series are not great. Compared to DSLRs, the batteries drain many times quicker. The A7sii doesn't seem to change much either. However this can be easily alleviated by getting extra batteries. The W series batteries for the A7 series are quiet cheap these days and there's lots of third party brands from Wasabi that are much cheaper and operate well enough for the price. Bringing an extra 2-3 batteries doesn't add too much space or weight. Additionally you can charge these cameras while shooting with a simple battery bank and a micro USB cable.8. Image quality. Overall the sensor is super sensitive. The only downside to the camera is the low resolution. Again, I realize this is mainly geared towards video and not made for photography and the resolution is good enough for 1080p and 4k recording. However for photography 12mp is not enough to pick up fine details, textures, and cropping. While shooting you can crop maybe 10% but any more and you get a super low resolution photo which for professional shoots may not be suitable. If you don't nail the composition in your shot, you don't have much leeway in post processing to make it better. It really requires an experienced photographer as the resolution is not forgiving for mistakes.Overall this camera is the real deal. Even though it's an older camera, in 2019 there's still no challenger for a low light king. The only thing that may come close would be an A7siii which is supposed to be releasing soon. This camera allowed me to take shots simply not possible with other setups. When went to Iceland, I brought an A7sii and A7rii. When trying to capture the northern lights with the A7rii I had to do a lot of post processing trickery in order to make the green northern lights visible. With the A7sii, every shot of the northern lights had bright green lights! No editing was needed to make the lights visible. The camera can see the northern lights even when my eyes could not. It was there that I realized just how sensitive the A7sii sensor was, it could see spectrum that were not visible to human eyes. That's the best compliment I can make.***If this was helpful for you, please give me a helpful vote! Thanks!***