Samsung R&D head talks chokepoints in Z Fold 3 and Z Flip 3 development

With the third iteration of Samsung's foldable unveiled, Samsung hopes they will provide the 'sustainable growth' for making the new category mainstream.
Written by Cho Mu-Hyun, Contributing Writer

(Image: CNET)

Samsung's three mains goals behind developing the new Galaxy Z Fold 3 and Galaxy Z Flip 3 foldable smartphones were to offer meaningful experiences, durability and reasonable pricing, a company executive said.

Samsung Mobile executive vice president and head of flagship product R&D team Won-Joon Choi told ZDNet that the company believes these three factors for its latest devices will be what takes foldable smartphones mainstream

"We are confident that the foldable smartphone category will grow. And that growth needs to be sustainable," Choi said. "So for us, the big question was how can we offer a new value that is worth what our customers are paying for these devices. That cannot be the novelty factor of folding alone."

According to the executive, Samsung conducted lots of consumer research prior to and during the development of the Z Fold 3 and Z Flip 3, and one important part of that was finding out customers' willingness to repurchase a foldable smartphone. Many of the new functions and experiences on the devices were a direct result of that research, Choi said.


According to Choi, the Z Fold 3 and Z Flip 3 are not about showing off the company's folding technology, but the experience they offer. Samsung collaborated with Google to integrate the Android operating system into the folding devices. It also reached out to hundreds of third-party app developers to convince them to join the foldable ecosystem, the EVP said.

Choi also talked up Samsung's Good Lock feature -- an app that allows customisation across themes and user interface for Samsung devices -- and how it can be used in foldable devices to boost user experience. Some of the app's features in the Labs menu can be used to customise certain apps such as Instagram to reduce black spaces and integrate better with the folding screen, he said.

"We think we've reached a certain completeness when it comes to the folding form factor experience. We've reflected on customer feedback a lot. But we can't do it alone. We need third-party developers to join us in developing apps that support flex mode, large screens, and multi-window setups," Choi said.

Adding in S Pen support for the Z Fold 3 was also part of Samsung's efforts to offer a meaningful experience on the device, he said, but that was extremely difficult. 

"There were times we wanted to give up on the feature. The technology to support the stylus for the foldable form factor wasn't done in a year, but it was years in the making."

The rectangle-shaped digitiser sheet under the display, which finds the location of the pen's tip through resonance sensing, is made with hard material and is not flexible like the display panel. Samsung initially intended to have the digitiser as one sheet under the panel, but after repeated failures to make this functional, the company came up with the simple solution of cutting it in half and putting one digitiser on each side of the fold, Choi said. 

"We made sure the two digitisers shared their signals and also applied our writing pattern prediction algorithm to make the stylus work between the gap."

For the tip of the S Pen, Samsung also collected data on how much force could be generated when customers pressed it strongly against the display panel to protect them for scratches.

On whether the company thought about housing the S Pen inside the Z Fold 3 as it did for the Note series, the executive said the company considered lots of options on how to incorporate the stylus for its folding devices.

When deciding to not house the S Pen in the Z Fold 3, Choi said the new foldable is 6.4mm in thickness when unfolded, thinner than the Note series' around 8mm, which meant if the pen was housed inside, it would be too thin. 

"If the pen is too thin, it ruins the feeling of writing. We thought a lot about benefits and trade-offs when it came to how we wanted to present the S Pen on the Z Fold 3."

However, Choi did acknowledge the benefits of housing the stylus inside a phone and said the company would continue to "think outside the box" to come up with the best solutions for the S Pen.


Samsung Mobile executive vice president and head of flagship product R&D team Won-Joon Choi gave the lowdown on Galaxy Z Fold 3 and Galaxy Z Flip 3's development process. 

Image: Samsung


According to the executive, durability was one of the top priorities for the Z Fold 3 and Z Flip 3 as consumer feedback showed that one of their biggest concerns was around the durability of the devices.

"The display panel and the hinge are the most important factors in terms of durability," Choi said. "For the display panel, we observed all the defects such as scratches that have happened in the prior iterations. These display panels have very complex layers and we have to make these layers flexible and robust at the same time.

"We mulled over the right thickness of these layers, the materials we use for them, adhesives, and the cover film."

For the hinge, the most important component in both devices for achieving the IPX8 water resistance rating, Samsung focused on making the structure simpler. The Z Fold 2's hinge had over 100 components but for its successor, this number has been halved, Choi said.

"We tried to reduce the process steps to manufacture the Z Fold 3 and Z Flip 3 as well as their components all around. We also optimised the materials so that they are strong, water resistant, and cost-competitive."

This innovation in design and materials also allowed Samsung to achieve a lower price tag for the devices to make mass producing them simpler, the EVP added.


The screens of the Z Fold 3 and Z Flip 3 both mark the first time a foldable has supported a 120Hz refresh rate, and the Z Fold 3 is the first time Samsung has implemented an under-display camera. Samsung touted both features heavily in its Unpacked event, but Choi noted that the development processes for both features were not without hurdles.

"A 120Hz refresh rate on the foldable screens was a challenge because of their higher power consumption as the screens are generally larger than conventional phones. Scrolling through them also needs to feel natural. We have tons of experience in software tuning optimisation, which allowed us to over this challenge," Choi explained when touting the new feature.

While energy efficiency was the challenge for upping refresh rates, the under-display camera posed a problem for Samsung regarding how to make the image sensor properly absorb light, which meant the company needed to complement the new hardware with software to produce images it was happy with. 

Unlike conventional front cameras that don't have a panel covering them, under-display cameras are unable to fully absorb light due to being blocked by a display.

"Since now there is a display panel above the camera, we had to find ways to minimise the loss of light when it passes through the display panel to reach the image sensor," Choi said.

"The key to achieving the under-display camera feature was the image restoration algorithm we used. The software will work to recover the image or video to their full content if it detect shortcomings."

In talking about the new under-display tech, Choi also said the Z Fold 3 complemented the other camera options available on the device, such as using the main camera to take selfies in flex mode.

Image: CNET


The Z Fold 3 and Z Flip 3 each sport a triple 12MP camera and double 12MP camera, respectively, as their main shooters.

Strictly in terms of pixels, this is behind the specs of cameras put in conventional flagship smartphones. The Galaxy S21 Ultra, for example, packs a 108MP main shooter.

On whether Samsung plans to boost the hardware specs of the cameras for foldables, Choi said: "How many cameras there are and what pixels they have is of course important, but we felt the overall experience of how the cameras are used is more important. So we are focusing on putting on our resources in camera software right now."

Addressing the two form factors presented in the Z Fold 3 and Z Flip 3, the EVP said Samsung is still continuing to review other form factors but will only launch them if they add something new and useful.

"The important questions is whether a new form factor can provide an experience that wasn't available before. We do feel however that down the road there will be a time when we can introduce a completely new experience in the foldable space," he added.

Updated at 11:12am AEST, 16 August 2021: clarified Samsung Good Lock feature's capabilities and the Z Fold 3's measurements.

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