One of the biggest complaints we hear about from photographers today is lack of innovation by DSLR manufacturers. Given how far mirrorless cameras have gotten in the last few years with the electronic viewfinder (EVF) technology, it is a given that DSLRs are looking archaic in comparison, particularly when it comes to intelligent information overlays, manual focusing, focus peaking, EVF image playback and other important advancements that make mirrorless cameras not just joyful to use, but also very helpful in reducing focus issues. When using classic lenses such as the Noct 58mm f/1.2 on a DSLR, I personally find it quite frustrating that I have to switch to live view to try to nail focus with the camera at my arm’s length. Not only does that result in potential instability and undesired camera shake, but it takes me away from the optical viewfinder (OVF) and slows down the whole process. But what if there was a solution to the problem? What if DSLR manufacturers came up with a way to integrate an EVF into DSLRs and make both OVF and EVF possible? Sort of a “transitional DSLR” with both OVF and EVF capabilities. How cool would it be, if you could switch from an OVF to an EVF with just a single button? I have been thinking about this concept for a while and I think there is a way to implement this, if camera manufacturers are willing to be flexible and put some R&D resources towards such a project. It would certainly reduce the potential of mirrorless cameras taking a huge market share away from DSLR sales, which have only been declining in the past few years.
The Mirror
When it comes to mirrorless vs DSLR, we know that DSLRs have a physical limitation in terms of the flange distance (which is the distance between the mount and the sensor) – due to the presence of a mirror and the lenses which have been specifically designed for such flange distance. Therefore, DSLRs will always have the additional bulk, at least in terms of camera width, when compared to mirrorless cameras. Although at some point in the future the mechanical mirror and the pentaprism most likely will have to be abandoned completely (once EVF refresh rates and overall responsiveness get as good as OVF), providing both OVF and EVF capabilities at this point would be an ideal solution in my opinion.
DSLRs still reign supreme when it comes to fast phase detection autofocus, start up time, shutter response and the choice of native lenses available at the moment, particularly super telephoto lenses with exceptionally fast focus motors. If you don’t shoot sports and wildlife, you might have talked to friends who do, and you know they will laugh every time they hear the words “mirrorless” and “action” together – despite all the efforts to make mirrorless cameras fast in AF speed, we know that mirrorless has a long way to go not only in terms of improving AF speed and accuracy, but also in providing solid native-mount lens choices for professional needs. As of today, not a single mirrorless manufacturer offers anything professional-grade above 300mm without use of messy adapters.
So if DSLRs were modified to be able to switch between OVF and EVF, they would give the best of the two worlds in a single package. Sports, wildlife photographers and those who prefer OVF would continue enjoying the benefits of classic DSLRs, while everyone else would have the choice to switch to EVF if they desire. But how would it be possible to achieve such a task?
The first answer lies in the mirror mechanism. All current-generation DSLRs already have the capability to switch to live view mode, where the image is projected on the LCD directly from the image sensor. In this mode, the mirror goes up and stays locked up until the photographer leaves the live view mode. Leaving the mirror raised does not consume a lot of battery life – what drains the battery are the sensor and the LCD actively capturing the live data. So there is no concern with leaving the mirror locked up in this position – having been doing a lot of videography lately, I can say with confidence that practically every DSLR today can easily do this already!
Here is a diagram of a DSLR in Live View mode:
As you can see, light rays are passed right onto the sensor in this mode. Note that the pentaprism is blocked in this mode, as explained below.
The Pentaprism
The second answer lies in the pentaprism, which is what flips and mirrors what you see through the lens into the viewfinder. The moment the camera mirror is raised, the pentaprism goes dead, as the light is completely blocked by the mirror (as illustrated above). This is why OVF is only available for us before or after the capture – you cannot see a thing when the camera is in the process of capturing an image, or when the camera is used in live view mode. The below diagram shows the normal operation of a DSLR, where the mirror optically projects the image into the pentaprism:
Now the biggest issue lies in the implementation of an EVF with the pentaprism in place. In mirrorless cameras, there is no pentaprism, since there is nothing to optically project into a viewfinder. Instead, there is a small digital screen (similar to an LCD screen on the back of the camera) that sits inside the viewfinder. So how can a DSLR integrate a digital screen inside the same area where there is an optical viewfinder? This is where the biggest challenge lies – engineers will have to think of a way where to best put the digital screen. Personally, I would propose to put the screen on the opposite side of the pentaprism, as illustrated below:
When the pentaprism is blocked by the mirror, the OVF goes completely black. Putting an EVF on the opposite side of the pentaprism would project the image just like it is projected normally, except the screen would only turn on in live view mode, when the mirror is raised. In normal mode with the mirror down, the screen would go black, essentially serving as the back side of the mirror. Considering how thin and tiny OLED screens are today, adding one right behind that area should not be an issue and should not result in a bulkier top of DSLRs. If putting an OLED screen where I indicated has space or other constraints, it could also be placed on the top of the pentaprism. The image would have to be turned upside down, but it would technically work.
I thought about other ideas on where to put the EVF, but they are going to be much more difficult and technically challenging to implement. For example, another idea would be to place the OLED screen right in the focus screen under the pentaprism, but since the OLED screen cannot be made semi-translucent, it would have to be mechanically inserted in live view mode and taken out in normal mode. Not a good idea at all, since it would only increase the complexity and result in another mechanical component that might fail at some point.
The Results: No More Focusing Issues!
The idea of a “transitional” DSLR sounds really good to me personally. It would give us both OVF and EVF in a single package and provide innovative features that DSLR users are craving when they are looking at mirrorless cameras. It would allow us to use our native-mount lenses that we have acquired over the years. It would make manual focusing a breeze and not keep us away from other technological advancements we see today. In the meantime, DSLR manufacturers could take this concept a step further – add phase detection pixels on sensors for faster focusing in EVF mode (this technology is already available) and further work on increasing AF speed in such mode. In addition, it would be wonderful if DSLR cameras had the capability to self-calibrate the phase detection sensor – now that would be a game changer! If phase detection sensors are on the sensor, the camera could probe for focus in live view / EVF mode and when a subject is in focus, calibrate the phase detection sensor so that it focuses exactly the same way. This would address any focus issues that we presently see on DSLR cameras. And we could take this a step further in terms of lens calibration too – have the phase detection sensor automatically adjust focus on each lens too! Since the camera would know exactly where focus needs to be, as it is already projected on the phase detection sensors on the image sensor, all focus issues could be completely addressed with such a system.
Does this sound too good to be true? Would love to hear the thoughts of our readers!