The age of smartphones has seen Japanese veterans like Sony lose ground. Between Korean companies like Samsung and the rising might of Chinese, the old giants have lost some of their sheen. Sony still manages to release some interesting products, such as the flagship Sony Xperia Z3 (Review) and Sony Xperia Z3 Compact (Review).

Some of the engineers from the Z3 team were recently visiting India, and met up with NDTV Gadgets to talk about the creation of their leading products, and share some of the insights that emerged from the design process.

We spoke to Yoshikazu Sakamoto, Senior Project Manager, Product Program Office; Hiroshi Takano, Deputy Head of Research Tokyo; Shimpei Yamaguchi, Mechanical Engineer - Concept and Technology Advanced Design Department; and Yasutaka Kashiwagi, Base Band engineer, PD5 Product design, Hardware. Sakamoto, who has worked with Sony for nearly 10 years now, tells us that the total Sony Xperia Z3 team has 300 engineers.

Takano was the most precise of the four engineers, and carefully corrected his co-workers on percentages and other details, while talking about his speciality - the camera technology. He started off the discussion with a small presentation showing off the camera improvements that the Sony Xperia Z3 has over the previous version.

"We were able to use more of the expertise of the Cybershot team at the parent company," says Takano. "One of the biggest benefits, from Sony [parent company], is the software. A good picture is a combination of good hardware and good software."

Sakamoto also added that the camera modes that Sony comes with also make it simpler for anyone to take a good photo. "There is the Auto mode, and there is the Superior Auto. Superior Auto, the camera analyses the scene, and then the software can decide what type of photo you are taking," explains Takano. The object recognition software can then fine tune the camera settings to get the image that it believes you are trying to capture, balancing the exposure, the focus and the colour settings automatically behind the scenes.

There are some drawbacks to Sony's approach - if you choose to stick to Superior Auto, then you don't have too much control over the shots you take. But when you change the modes, you see a bewildering plethora of options. Unfortunately, these are all variations of automatic settings, with certain presets, which means you can't directly take control of the camera's settings - that's one of the key differences between using a real camera (for which these modes were designed) and a smartphone.

Takano then showed us a cross-section of the phone so we could look at the camera module, and compared it to the camera module used in the Sony Xperia Z1. He showed us how the module was fitted in the phone, and said that the company had managed to shave 0.7mm off from the size of the new phone partly by making this module thinner.

When asked if this came at the cost of the camera performance, Takano said that there was some sacrifice made - that an even bigger camera could be even better in terms of image quality. We asked if a small bulge - similar to the new iPhone models - would have led to better images, but Takano and Sakamoto did not comment on that.

Sakamoto only says, "We kept pushing them, to make it fit, without giving up on quality. The results are stunning, and the camera is flush with the body," a clear reference to Sony's tweet last year during the iPhone 6 launch, which took a dig at the protruding iPhone camera.

Yamaguchi, the mechanical engineer, says that the smaller camera module was essential in allowing the sleek design of the two flagship phones.

"Earlier, the camera module was bigger, so we kept it next to the display module. It was almost as thick as the phone," Yamaguchi explains. "Now, the module is much smaller, and we were able to sandwich it between the display module and the case of the phone, saving more space and making the phone smaller without sacrificing on quality."

Yamaguchi looked the youngest of the four engineers, and kept glancing at his Sony Smartband Talk since the engineers had a flight to catch after the meeting - but not before giving us a good look at the inside of both the Sony Xperia Z3 and the Z3 Compact.

Yamaguchi says that waterproofing the phones was not too challenging, and did not require compromise from a design perspective. As Sakamoto points out though, the IP65/68 rating that shows how resistant the phone is to dust and water also makes the Sony Xperia Z3 more expensive for the company to produce.

"We have to test everything to make sure that it is actually water proof and dust resistant," Sakamoto says, "We [have to] stress test all the models before we sell them."

Yamaguchi gave us a little more detail.

"We use a special vacuum test, to confirm that the phone is actually waterproof," he says. "There is a special hole, it's an invisible hole [here, all four engineers conferred in Japanese for a few moments, as if trying to find a simplified explanation we could follow in English] like a grill."

He then showed us a small mesh on one corner of the inner body of the phone.

"We immerse the phone, and then we place it under a vacuum," Yamaguchi explains. "The mesh is specially designed, so air can come through, but water cannot. So by doing this, we can vacuum the phone and see if any water comes out." If no water comes out, that shows that none entered the phone during the immersion test.

The actual waterproofing technology is one where Sony has made some important advances. Yamaguchi showed us a clear sheet of plastic that is embedded around the body of the Z series phones. This layer seals in the phone, and protects it from water - Yamaguchi tells us that this is fitted in the phones using laser technology.

"Earlier [we] did not use laser to attach," Sakamoto explains. "It used to press the two parts together."

The seal would be heated and bonded using a mechanical process, which led to a slightly bigger phone. Using a laser to burn away the excess material while bonding the seal, Sony was able to reduce the size of the bezel, Sakamoto tells us.

So what comes next? Can the miniaturisation of parts continue, and what impact will it have on the design of the phone? Sakamoto tells us that Sony's flagships are unlikely to change in their basic design anytime soon.

"We are always looking, and will update the design when it is needed," he says, "but we don't want to abandon our identity either." He predicts that Sony's design language (called Omnibalance) will stay for a whlie.

Yamaguchi however tells us that the company is continuing to study new materials and experimenting with how different substances could be used to make phones.

"We can't do much to the basic design. Because the customer wants the biggest screen with the smallest body possible," he says. "With new materials, we could make some changes to the feel of your phone."