The ASUS ZenPad S (Z580CA) Review
by Brandon Chester on August 31, 2015 8:00 AM ESTCamera
While most people will use either their smartphone or a dedicated camera for taking photos, a tablet can be used in a pinch. Some people even make their tablet their primary camera, whether it be because it's their only device, or because they prefer the larger viewfinder that a tablet offers. While many may still find the idea of taking photos with a tablet to be absurd, one need only look at the people around them to see that for one reason or another tablet photography has become a way that some users choose take photos.
The ZenPad S Z580C sports a 5MP rear-facing camera, and the Z580CA bumps that to an 8MP sensor. Since resolution is only one of many aspects of a device's camera system, I've included some more information about the ZenPad S Z580CA's cameras in the chart below
| ZenPad S (Z580CA) Camera Specifications | |
| Front Camera | 5MP (2592x1944) |
| Front Camera - Sensor | Omnivision OV5670 (1.12 µm, 1/5") |
| Front Camera - Max Aperture | F/2.4 |
| Rear Camera | 8MP (3280x2464) |
| Rear Camera - Sensor | Toshiba T4K35 (1.12 µm, 1/4") |
| Rear Camera - Focal Length | 3.0mm (28mm eff) |
| Rear Camera - Max Aperture | F/2.0 |
The ZenPad has a similar camera stack to the ZenFone 2. Toshiba's T4K35 sensor has a resolution of 8MP with 1.12 micron pixels, while the ZenFone 2 used T4K37 which had the same pixel size but a higher 13MP resolution. Lens aperture and focal length end up being the same as the ZenFone 2 as well.
To evaluate the still image quality of the ZenPad S I've taken photos of my standard photo scene during the day and at night, and compared the results to the other tablets that I have available for testing which includes the Nexus 9, the iPad Air 2, and the Dell Venue 10 7040.
It's clear that the ZenPad S suffers from the exact same processing issues as the ZenFone 2. There's far too much sharpening of the image as well aggressive noise reduction. This can be easily seen in any of the foliage in the frame, and in the lines separating the bricks of the school walls. There's also noise across the entire sky, despite this photo being taken with enough light for the camera to shoot at the base ISO of 50. The still image section of my ZenFone 2 review goes into more detail on these issues, and it's disappointing to see that none of them have been resolved. Relative to the other tablets in my comparison, I would have to say that the ZenPad S takes the lowest quality photos. The exposure and color accuracy is much higher than the Dell Venue 10, but the extreme oversharpening and heavy noise reduction makes the image look more like a painting than a photo.
In low light the ZenPad S continues to perform poorly. Low light scenes really make it clear how much of a photo's quality has to do with the quality of the image processing performed. Both the Nexus 9 and iPad Air 2 share a sensor size and resolution with the ZenPad S, and both actually have smaller apertures. Despite this, they both have a better exposure and a much greater level of detail than the ZenPad S. Unlike the day photo test, I would say that the ZenPad S did take a better photo than the Dell Venue 10, but only because I can't even begin to describe the problems with the Venue 10's photo.
Ultimately, the ZenPad S suffers from the exact same issue as the ZenFone 2, which is poor image processing. The color rendition and exposure of images taken during the day makes it clear that the camera has potential, but the numerous issues with the processing produces poor quality images.
WiFi Performance
Like the ZenFone 2, the ZenPad S Z580CA uses Broadcom's BCM4339 WiFi + Bluetooth solution for wireless connectivity. The implementation in the ZenPad S supports two spatial streams on 802.11ac, which allows for a peak theoretical link speed of 867Mbps. However, the ZenPad S has a software problem that makes real world speeds significantly lower than that.
You may be wondering why the ZenPad S can only get a maximum speed of 173Mbps over UDP when the ZenFone 2 with its 1x1 802.11ac goes as fast as 293Mbps. You may have also noticed that a speed around 150Mbps is very similar to devices with 2x2 802.11n WiFi, and that's exactly the problem. The ZenPad S only works in 802.11n mode, a software problem that should have been found in testing long before the tablet actually shipped. I have tested the ZenPad S with an Apple Airport Extreme 6th gen and a TP-Link Archer C7, and the max link speed remains at 200Mbps in both cases. ASUS has confirmed the issue on their end and is aware of it, and so a software fix should arrive for it at some point. Users are, at the moment, just going to have to live with WiFi that isn't even half as fast as it would be if it was working properly.
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PixyMisa - Monday, August 31, 2015 - link
I have two Nexus 7 2013s (one died and wouldn't charge any more, but a wireless charging pad brought it back to life).Still holding on and waiting for something better that doesn't cost three arms and a leg.
I also have an Xperia Z Ultra that I picked up cheap. That's not bad, but a little on the small side for tablet use.
Sunburn74 - Monday, August 31, 2015 - link
Does Anandtech plan to update the review once a stylus is available? For some of us, the stylus input would be a real deal maker (or breaker if it is subpar).Brandon Chester - Monday, August 31, 2015 - link
I specifically asked ASUS to send the stylus and cover if they could, but all I got was the tablet. I have to send this back so I doubt I'll ever be able to look at the stylus. I really wanted to.vladx - Monday, August 31, 2015 - link
What nonsense is this about the camera? The day photo definitely looks the best along with S6 Edge one. Saying the iPad one looks better is a joke.The rumours are true, this site is more and more biased by each day passed.
Brandon Chester - Monday, August 31, 2015 - link
I don't know if you viewed them at full size or not but ASUS's camera processing has been widely panned by pretty much every site that looked at the Zenfone 2, and it is literally unchanged here. If there's some level of bias there then it must exist at every tech site ever.The image quality is not even remotely comparable to the shot from the S6 Edge. A good area to examine is the walls of the school, they're completely destroyed by heavy noise reduction to the point where the lines start curving and shifting. It's just not a good image.
DanNeely - Tuesday, September 1, 2015 - link
It's really that the problems are only obvious in the full size image. The resized images in the gallery aren't large enough to see the problems.This's a sitewide comment, and not directed at you personally; but people who look at the full size images as well as the ones in the gallery are probably in the minority. I think a set of 1:1 crops of a detail area or two that make things like the destructive processing the Asus does readily apparent would really make problems more apparent.
eek2121 - Tuesday, September 1, 2015 - link
I didn't even finish reading the first page of this article and I thought to myself...ASUS made the nexus 7. Why the hate?Michael REMY - Tuesday, September 1, 2015 - link
as Anandtech still continue to ignore sony xperia tablet, i can not consider seriously this review of the asus zenpad. i trust all the review of Anandtech else the tablets ones! I hope one day you could try or review the xperia z3 compact tablet or even the xperia z4 tablet because it changes all the done and the way to judge the other tablets on the market.DanNeely - Tuesday, September 1, 2015 - link
It's not AT ignoring the Sony Tablet. It's Sony ignoring the tech press. AT (among others) have regularly asked for review samples of various products. Sony's almost never willing to provide them. As a result they get next to no press coverage beyond demos at big shows and product release announcements. That's entirely on them.MrSavage - Tuesday, September 1, 2015 - link
People running big websites aren't capable of buying a review unit off a store shelf? Imagine that. Having to pay for a review unit? Perhaps giving it away later as a giveaway contest? Nobody knows about tax write offs? Sure, if it's not free then we don't review it. If it's the best tablet on the market who cares. We won't inform our site visitors of that great product because there was no freebie sent out. Credibility wise, I would not be saying this is great or the best because I chose not to review other top tablets because I didn't get a free one in the mail to review. I wish sites were open about the bias or friendly handshake agreements. The best tablet of the free ones sent out to big websites. Not the best, but just the best from the ass kissing companies who sent out review units. Sad excuse in my books. I call it a disservice to my visitors if that's my mentality.