04.07.2017 FUJIFILM

GFX Technologies #7 - The Development of the Ultimate Finder

This story is about the GFX’s electronic viewfinder. The phrase “seeing is believing” is exactly what’s needed to be said about it. It has the world’s highest viewfinder magnification ratio of 0.85x. You will see the impact when you actually use it yourself.
So you can believe it when you see it, but how does this finder actually work? For photographers, all they can see is the eyepiece part of the finder, but certainly there is more than just an eyepiece.

1. The Finest Panel

To create the ultimate EVF, the finest panel should be used to display information. For the GFX 50S, we decided to go with a 0.5-inch approx. 3.69 millions dots OLED panel. The bigger the panel more advantageous it is to deliver higher image quality. For one, pixel counts can be increased. Secondly, there will be less reliance on the optical devices. However, increasing the size and pixel count do not simultaneously equate to an improvement in overall viewing performance of the EVF. In order to achieve the improved performance, the response, color range, and contrast also need to be fine-tuned to work with the bigger panel.

What you see is what you get with the EVF, so it is important that accurate information gets delivered. The change in color temperature, dynamic range, or exposure setting should be true to the final result. We use an OLED panel because it achieves the optimal balance of all things considered.

2. Luxurious Lens

As mentioned in the last paragraph, theoretically speaking, there should be less reliance on the optical parts when using a bigger panel. Unfortunately it does not work that way in reality. In order to achieve a 0.85x magnification view, higher reliance on optical parts was inevitable.
This is where the designers brought their craftmanship to the table with the latest technologies in hand. To compensate the higher reliance on the optical parts, they proposed a lens construction of 5 elements in 5 groups (all glass and including 2 aspherical elements), which is unheard of for a finder, in terms of both cost and size. This was only possible because it was designed for the GFX 50S.
The finder’s view is very pleasing to the photographer’s eye.  Generally speaking, if you go as high as 0.85x magnification ratio, aberrations will be very noticeable. Thanks to the luxurious lens construction, the EVF achieves minimal distortion and color aberration to deliver clear and sharp images.

3. Last Element

When talking about optics of a finder, it is important to know that we consider your eye as the final element. A finder is never complete without your eye.

Sure enough, photographers put their eyes to the best position to see through the finder, but the “last element” is never fixed in its position. This is the biggest difference between the finder’s optics vs photographic lenses.

How does the viewfinder look like when the eye is in the optimal position? And when it is not in its optimal position? The designers incorporate these assumptions into the lens design.

Here at Fujifilm, we refer this movement as “eye swing”. The optics are designed to make sure that viewing is least interrupted by the eye swing . We also design the optics so that the finder guides the photographers to settle on the optimal position. The designers take all these into consideration when creating the finder optics.

4. From the Length of 3cm to 20cm with 4 Connecting Parts

The charm of the GFX 50S’s finder is not just the view. The finder is detachable, and can be positioned in various ways by using the optional tilt-adapter. You can position the finder in many possible ways. How is this achieved?
As long as the finder is electrically connected, you should obviously be able to view the display. The problem arises when you try to connect a finder that is not built directly onto a camera body, like the GFX 50S. In addition, there is the challenge of creating an EVF that can also be connected to a tilt-adapter.
For the X-T2, the finder is built-in on the camera body, and its total transmission length is a mere 3cm. It will never be longer than 10cm in any case. But for GFX 50S, the length is extended up to 20cm, and there are four connecting areas. The length is longer; however we could not reduce the amount of the signals to deliver high image quality.
We worked out the problem by impedance control based on board pattern and contact design. We also installed a micro-computer on the finder. By doing this, although it is an external accessory, it becomes a part of the main body when attached, so the signals can be trasmitted efficiently with minimal information.
GFX 50S achieves a display time lag of 0.005sec, which is the same as the X-T2.

5. All Metal Parts

Lastly about its exterior.
Magnesium is highly durable. This material is used on the GFX 50S body, so it is only natural that the EVF also used the same material. The only problem is that the EVF has movable parts. The tilt adapter’s construction should also be considered.
We ended up using two types of metal. We created some of the parts by a Metal Injection Molding Method to create movable parts and hinges. This is the same technique as the X-Pro2’s ISO dial. It is costly, but the durability and processability is top notch. In addition to durability, the movable part is required to have a good feel during operation. This pleasant feeling comes from notches that have been engraved using the with M.I.M. method.
Another material used is ultra-duralumin. It is lightweight and robust. As a result, even if the part becomes thick and big, it can be surprisingly light.

These are the five points of developing the GFX 50S’s finder. As we said in the beginning “Seeing is believing”. Test it yourself, if you have not already done so.