[kadajawi]

Hello there,
question: Can a hybrid viewfinder be done. One that lets you have an optical viewfinder with a full color overlay of informations, as well as the ability to display the live view feed?

This whole thing started in the What should Pentax do? thread, but got a bit out of hand. I first quote from those threads, but below that there'll be a quicker summary and additional thoughts.

Hmm... I'm worried a hybrid viewfinder might compromise both the EVF and OVF parts (or just the OVF, that would be equally unacceptable).
But it depends on the implementation. If it's a contraption similar to what Sony used - some mechanism for switching between the optical and electronic image - it would be bad, probably very bad. Imaging splitting devices would steal light. However, if they can replace the matte screen with a transparent see-through display it could work pretty well - assuming they can find a panel (OLED?) with high transmittance and no color cast.
I'm no camera engineer though, so I'm waiting to be amazed.

I don't think it would. Maybe the EVF part, but certainly not the OVF part. Basically my suggestion is... you know these red squares inside the viewfinder that light up when a point is in focus? You can't see them otherwise. You can see the location of this here, the article points out where it sits: Pentax K-30 vs K-5 IIs Cross Sections - Photokina 2012 | PentaxForums.com

I used to think it's some kind of etched glass perhaps with LEDs that can shine on them, or something like that, but really it's that thing between the Pentax logo and one of the sides of the pentaprism, the last before it goes straight to your eyes. Could be like those old LCD screens on watches that glow red. In any case, the pentaprism seems to act like a one way mirror/glass... like they'd use in interrogation rooms. As long as it's dark in the room behind the mirror, you can't see what's there. Turn on the lights, and you see what's behind. So you can overlay data with a screen that sits outside the pentaprism as long as that image is brighter than what comes from the sensor. You can't darken anything. Over dark/black parts however that screen is able to display data or an image. Fold up the mirror and it's black in there, all you'd see is the screen. If you want to display additional data you'd have to make the screen bigger, and you can use the areas surrounding the image from the mirror to display that data... like for example more detailed information coming from the multi segment light meter.

I don't see any problems with this idea, as all our cameras already feature a display in that position, all that's needed is a much finer multi color display, and those exist. The red squares are in focus, so I suppose the screen should be too? The only thing that worries me is that they seem to use a prism to redirect the light from the little screen to the pentaprism, instead of directly making it touch it. Perhaps something related to having the same distance so the eye doesn't have to refocus? In that case the area between pentaprism and Pentax logo would need to be extended in order to fit the screen, but that seems to be a rather small trade off, and none that should influence the camera size too much. With a lens mounted it will always be much bigger anyway.

Fuji btw. also uses a prism for their hybrid screen. That way you don't need to have a transparent screen as I thought you'd need to have. The transparent OLED screens I have seen are sort of transparent, not properly transparent. When not displaying anything they seem to be rather grey, and that with not so high resolutions. I imagine it gets worse with higher pixel densities.

I hope Ricoh has some serious OVF technology coming. The EVF doesn't provide the experience that the OVF offers, but the advantages with AF accuracy, metering, color/WB are bigger than the experience. Its the IQ that ultimately matters the most.

Can Ricoh design an OVF system that eliminates front/back focus or focus shift?

Take shooting in the snow as an example. With the OVF and a DSLR you have to manually increase exposure because the sensors are fooled by the white scene, but with mirrorless I can see what the sensor sees. The EVF doesn't have the DR of an OVF, but neither do my prints or the digital sensor.

Ideally if you have a proper RGB histogram coming from the light meter in the viewfinder, under the OVF image, you're able to judge how your exposure is going to turn out even without seeing the actual EVF image.

I'm wary of being told "all that's needed is..."; it's usually some boss actually telling you "I want it done fast, don't care if it's hard or not".
Of course, it's not a "just put a better display in there". It's never that simple. First, EVF panels don't fit in there - a projecting system would have to be larger, and where do you fit it? Two solutions: extend the pentaprism housing forward (but can you? It's shaped that way to leave room for the lens), or use smaller OVF components. Second, the LEDs are projected only on the center of the viewfinder image, we'd need a system using all of it. Which means space.
Good point about the possible need for optics. Without the small prism, the LEDs and their focusing optics would have to be perpendicular to the prism's surface, hitting the lens mount.

Fuji is another story, a completely different viewfinder arrangement (no large glass pentaprism, more freedom in design, more space available).
I mentioned transmittance being a problem - and I'm not aware of any current transparent LCD having a transmittance higher than 30%. Obviously that won't work. Perhaps some one could solve this issue, or perhaps the solution is to project the image on a side of the pentaprism.

I think the idea of a hybrid viewfinder should be pursued (if only for video); but it won't be easy, some ingenuity and new technology would be needed. So I'm not expecting a working version soon.
Or perhaps we'll see something else, which would make the idea of a hybrid viewfinder look like an useless kludge. Who knows...

That's why I was asking, I'm sure there are smarter people able to tell my why this idea won't work. Do lenses exist that are huge right around the mount? The screen size needed for APS-C isn't as big as that for FF, so maybe this may only work for APS-C. Bezels around screens have become pretty small. I'd love to see how the light exactly travels inside the camera, and what exactly the components are. I guess the confirmation lights are directly behind the Pentax logo, then go through a mirror, a lens, a prism and then into the sensor. I suspect these many bounces around could be because the distance to the focusing screen, which is what the eye focuses on, is pretty big at this point. In that case, how about under the flash shoe? If the space is increased... Speaking of flash, the FF doesn't have an internal flash, which means the space that uses up is now clear. At least orientation wouldn't be a problem with a proper display, that can be fixed in software.

Btw., it looks like this camera doesn't have an AF confirmation light? http://upload.wikimedia.org/wikipedia/commons/8/8e/E-30-Cutmodel.jpg But it does have those lights. There are no lenses or mirrors or prisms around that pentaprism (apart from the status bar underneath the OVF, which is a very similar design to Pentax), and only one thing that seems to touch it that isn't part of the body. Looks like that part has some wires going into, so perhaps that's where the overlay is? It's on the top most side of the pentaprism.

It seems like there are plenty of different ways of placing the screen, http://www.ephotozine.com/articles/nikon-at-photokina-2012-20300/images/high...1348653961.jpg for example. Where did they place their screen in that beast? What is the thing touching the top most side of the pentaprism? Looks like there are these flat cables going there...

And Canon uses a transparent LCD... _1-12.jpg Photo by msowsun | Photobucket Maybe that's the difference between the cameras where you constantly see the location of the focusing points, with a couple of black squares, that are lit up when there is focus, and what we have in our Pentaxes, where you only see the points when they are lit up.

Sadly ifixit doesn't disassemble the whole top half of the cameras they disassemble, they only care about the sensor.

The idea of having an EVF is that you can use it during video shoots or when you would rather have live view. You can also have additional information displayed in the viewfinder, for example a RGB histogram (that may be fed by the RGB light meter Pentax uses?). You could much better see how the photo is going to turn out if you have that histogram, and if you understand how to read it. Another thing is that you could keep the mirror flipped up after a shot in order to review the photo, right inside the viewfinder. No need to take the camera from your eye, struggling to make a cup over the LCD screen trying to figure out what it displays because it's too sunny.

My idea is then to have the AF confirmation display replaced with an actual OLED or full color high res LCD screen. It seems to me that Canon does it in a boring way that we can't really apply for this purpose, they just use a transparent LCD screen with segments than can light up and, I think, are constantly overlaid. While it would be possible to install a LCD screen without the backlighting, and it should be trivial, I worry that it makes the viewfinder darker. And where do you get the backlight from?

The D4 shows how little space there is once you fit a FF sized pentaprism, I don't know where the AF confirmation screen is, and how it works. Could be Canon style, could come from somewhere else. Notice the huge lens above the extended pentaprism. http://www.ephotozine.com/articles/nikon-at-photokina-2012-20300/images/high...1348653961.jpg

However the K-5 (and K-50) is where it gets really interesting. It's quite obvious that the AF confirmation display is outside the pentaprism. http://gallery.falklumo.com/Photography/Camera-Tests/Pentax-K-5/IMGP7387/101...5_FvKA7-X3.jpg
The thing underneath the flash, right next to the Pentax logo, that's the AF confirmation indicator. The screen is right under the kink below the Pentax branding. It goes to a mirror, then an optical element, and finally a little prism that again redirects the light to the big pentaprism. It's beautiful!

A few things to note: The indicator goes through a lens and a small prism to go to the exterior of the pentaprism, the last reflection before it goes straight to your eye. It's taking up quite a bit of space, and consider that in the K-5 the focus points are pretty much in the center. Imagine how much bulkier it would be if they had the focus points spread all over the sensor? And this is APS-C. I am not sure Pentax can offer you a bigger focus point spread without dropping this beautiful bit of engineering and design (a focus point that is only visible when it's confirmed!). There may not be space for bigger lenses around the lens mount. This could end up being a problem with the FF camera, I'm curious to see how they will fix that (hopefully not by using a very center focused AF sensor).

At this point we run into problems. While putting in a small display should be possible, there seems to be no space for one that has at least the size of the OVF. You would have to make the camera thicker around the lens mount, which might give problems with certain lenses (not sure about that). Maybe with APS-C it can be done... There is also the part above the pentaprism, maybe that could be used with some rearrangements and a bigger housing. Seems like it is impossible to make the screen touch the exterior of the pentaprism, otherwise it should be pretty simple. But if they do that your eyes have to refocus to see what is displayed by it.

I wonder if getting the right distance is easier with the first point at which light is reflected in the pentaprism or at the second point (notice how the status display below the image you're getting from the lens is much simpler. There is a display that sits in the right distance, then a little prism that reflects it into the big pentaprism and you're done. No fancy optics.) I would say it's the first point, where the flash sits. It sits closer to the focusing screen. It also seems to have a bit more space, all that's there is a microphone, and that could be relocated. And one of those flat cables, I wonder what that is for.

I imagine this whole thing makes more sense in an APS-C camera, especially if you are able to have a bigger monitor in there than the mirror can offer. Not to say that a FF camera couldn't benefit either, and Pentax said they wanted to offer more than just the same that Canikon offer. No one else apart from Fuji has this kind of technology, and their cameras are very different. For me personally it'd be quite useful, I would really love to have this. And for those who couldn't care less... a similar camera that drops the optics and display could be sold for less, like the K-50 and K-500 brothers.

It seems like Nikon and Canon are working on this, having a couple of patents.
http://nikonrumors.com/2013/01/12/nikons-patent-for-a-hybrid-viewfinder-ovf-evf.aspx/
No clue how that is supposed to work though.

And http://gizmodo.com/389733/new-nikon-patent-brings-in-viewfinder-display-to-dslrs
Which looks similar to what I suggest, though for different (weird) purposes, and I wonder how that is supposed to fit. Plus the refocusing issues I think still apply. They also want to use a smaller screen...

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Last edited by kadajawi; 03-21-2015 at 08:38 AM.

[Winder]

I think the hybrid OVF is possible with today's technology.

1. COST - How much does it add? The high quality penta-prism OVF is already an expensive element. 100% coverage and calibrating the AF points in the OVF to the actual AF points has to be done by hand.
2. Size/Weight - How much more will it add to the size and weight of camera?
3. Accuracy - will it solve front/back focus issues or focus shifts? Will it accurately show changes in exposure as I adjust aperture/shutter speed/ISO?

All of these are important because the EVF provides all of these things for less money, in a smaller package, and with greater accuracy. Like most people I prefer to work with an OVF, but advantages of the EVF are very real and for many people important.

[kadajawi]

I think the hybrid OVF is possible with today's technology.

1. COST - How much does it add? The high quality penta-prism OVF is already an expensive element. 100% coverage and calibrating the AF points in the OVF to the actual AF points has to be done by hand.
2. Size/Weight - How much more will it add to the size and weight of camera?
3. Accuracy - will it solve front/back focus issues or focus shifts? Will it accurately show changes in exposure as I adjust aperture/shutter speed/ISO?

All of these are important because the EVF provides all of these things for less money, in a smaller package, and with greater accuracy. Like most people I prefer to work with an OVF, but advantages of the EVF are very real and for many people important.

1. Cost is a good question. Good screens aren't that expensive, but the additional optics, the engineering etc. add to the cost, plus of course if Pentax has such a stand out feature they may want to charge for it.

2. Good question. Not too much, I hope? Fortunately Pentax DSLRs are pretty light, so they may still be lighter and smaller than the competitors. But heavier and bigger? Probably.

3. In EVF mode, why shouldn't it? And if you have the histogram I think it'd be possible to do it in OVF mode too.

[Winder]

3. In EVF mode, why shouldn't it? And if you have the histogram I think it'd be possible to do it in OVF mode too.

I'm not sure you could have an EVF mode. I think you can project information into the OVF. Canon 7DII Canon DLC: Article: New Intelligent Viewfinder feature on EOS 7D Mark II but I don't think they have the technology to actually switch to an EVF and then back to an OVF. Can they project a histogram into the OVF that show changes to aperture/shutter/ISO in real time?

[kadajawi]

I'm not sure you could have an EVF mode. I think you can project information into the OVF. Canon 7DII Canon DLC: Article: New Intelligent Viewfinder feature on EOS 7D Mark II but I don't think they have the technology to actually switch to an EVF and then back to an OVF. Can they project a histogram into the OVF that show changes to aperture/shutter/ISO in real time?

What Canon does is have a black and white, non lit up (?) display sitting for example above the focusing screen. It's close to what they did so far, and nowhere near as sophisticated as what I suggest. I want them to have a big full color and backlit/self illuminated screen that is able to shine into the pentaprism to overlay the display. As a result if you stop the light coming in through the mirror (i.e. you fold it up) you have a monitor in there that can display anything you want, including what the sensor is getting. It's live view, but with a second monitor inside the camera.

I think doing a histogram should be possible. I mean the light meter is constantly reading the exposure, and Pentax claims the K-3 has a 86000 segment light meter.

You Tube

You Tube

The software just (?) needs to translate the reading into a histogram and apply the exposure settings... and it might even take into account the dynamic range of the sensor (raw image) and mark it down... drawing two lines. So you have a big histogram that displays the entire scene, and two lines that show where the camera will clip. If this works it would be pretty awesome. When you set it to exposure bracketing it could show which range is covered, and you can see if the scene fits in. Or perhaps an automatic mode that choses the amount of photos and their exposure to fit the whole scene into a bracketing, without having to take unnecessary shots.

Btw. it would be possible to drop the rear LCD if you have a screen inside the OVF, you could save a few mm and $ that way and make it look more like a classical SLR. If you need a big screen you can still use a smartphone/tablet for that.

[schneider]

The possibilties are limited compared to a liveview camera. The problem is that the mirror is in the way of the sensor, so the information can't be collected off of the imaging sensor. Therefore one would need to use something like the metering sensor, which can never be as exact as the actual imaging sensor. And obviously the camera should re-calculate the histogram to match the aperture that is chosen. A good optical viewfinder is beautiful, but it comes at a cost.

[Kunzite]

For the record, I'm not saying it can't be done - it probably can, but there are some technological challenges to be solved/worked around (space being only one of them). So we should not expect/demand Ricoh to make it work asap.
What can't be done is to extend the pentaprism housing forward; see the following image of a K-20D with a 16-50 (?), cut in half.
Booth Report: Pentax Corp.
The new D FA lenses are a bit fatter (see the next image).
http://i.ytimg.com/vi/Y6G10IN7CII/maxresdefault.jpg

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Last edited by Kunzite; 03-21-2015 at 10:53 AM.

[romay]

You could put a OLED screen in the optical path of the viewfinder without much hassle, but I don't think that's the biggest problem.
Using EVF, the mirror needs to go up which means you loose autofocus and metering.
So, you have to add PDAF and metering to the sensor, but then you have to remove both from the mirror path, as it's not economical to double them.
What you will end up with is a K-01 with an added mirror and viewfinder. Maybe that's not even a bad idea!
Problem will be the same as with all EVILs: sensor heat. Constant sensor readouts increase thermal noise. So your camera will suck at high iso no matter what.

[kadajawi]

The possibilties are limited compared to a liveview camera. The problem is that the mirror is in the way of the sensor, so the information can't be collected off of the imaging sensor. Therefore one would need to use something like the metering sensor, which can never be as exact as the actual imaging sensor. And obviously the camera should re-calculate the histogram to match the aperture that is chosen. A good optical viewfinder is beautiful, but it comes at a cost.

They are not. You can always fold the mirror up and use it like in live view. Like a mirrorless camera, with an EVF. This system should be ablr to enable both. The only downside is that you don't save weight or space like with mirrorless cameras. Otherwise it should give you mirrorless functionality and DSLR functionality... either or, and in DSLR mode even more.

The dedicated light meter is capable of sensing a bigger range, which can be useful, as I described. I trust Pentax that they can pull it off.

@Kunzite: I agree. I mean there is a tiny bit of space, but given that the screen right now is only 1/3rd the size that is needed (at least) and that the prism inside right now is covering 2/3rd of what is needed I have to doubt they can fit it. However if they move up the prism they have much more wiggle room.
It would be a larger camera for sure, but maybe not as bad as a 7D. A pro DSLR above the K-3.

---------- Post added 21-03-15 at 19:40 ----------

You could put a OLED screen in the optical path of the viewfinder without much hassle, but I don't think that's the biggest problem.
Using EVF, the mirror needs to go up which means you loose autofocus and metering.
So, you have to add PDAF and metering to the sensor, but then you have to remove both from the mirror path, as it's not economical to double them.
What you will end up with is a K-01 with an added mirror and viewfinder. Maybe that's not even a bad idea!
Problem will be the same as with all EVILs: sensor heat. Constant sensor readouts increase thermal noise. So your camera will suck at high iso no matter what.

It'd mostly be a DSLR, the EVF mode would be more like live view. However Pentax can use a sensor meant for mirrorless cameras. With PDAF and lower heat dispersion. I'm much more worried about getting a high quality screen in there that can stay all the time (i.e. overlay). The problem is IMHO keeping it in the right distance so the eye doesn't have to refocus.

Though I suppose the Fuji system could work. Have a display somewhere and redirect it via mirrors and prisms, then have it join the OVF light path via a prism.

[Winder]

They are not. You can always fold the mirror up and use it like in live view. Like a mirrorless camera, with an EVF. This system should be ablr to enable both. The only downside is that you don't save weight or space like with mirrorless cameras. Otherwise it should give you mirrorless functionality and DSLR functionality... either or, and in DSLR mode even more.

The dedicated light meter is capable of sensing a bigger range, which can be useful, as I described. I trust Pentax that they can pull it off.

@Kunzite: I agree. I mean there is a tiny bit of space, but given that the screen right now is only 1/3rd the size that is needed (at least) and that the prism inside right now is covering 2/3rd of what is needed I have to doubt they can fit it. However if they move up the prism they have much more wiggle room.
It would be a larger camera for sure, but maybe not as bad as a 7D. A pro DSLR above the K-3.

If what you are talking about were possible, then I think Sony would have done that instead of the SLT technology. Sony ended up with a bad compromise.

[kadajawi]

If what you are talking about were possible, then I think Sony would have done that instead of the SLT technology. Sony ended up with a bad compromise.

I disagree with that. Sony wanted to produce mirrorless camera with a live view feed that has PDAF. Since back then PDAF meant having a separate sensor, they kept the mirror.

However what I am talking about is having an OVF camera first and foremost. Fully OVF, but with more information being displayed, and a more flexible display. With the option of reviewing photos in the viewfinder, which allows you to keep the eye at the viewfinder, and which works much better on a sunny day.

In addition, sometimes EVFs have advantages, for example for manual focusing, for video shooting, in low light situations perhaps (depending on the sensor). In those situations you push a button and you get an EVF with those advantages.

The goal with these different technologies is entirely different.

The SLT technology has become obsolete, since you can put the PDAF sensor onto the imaging sensor these days. It was temporary technology, which is... bad for consumers. I want something that I know will exist in 10 years.

[Winder]

The SLT technology has become obsolete, since you can put the PDAF sensor onto the imaging sensor these days. It was temporary technology, which is... bad for consumers. I want something that I know will exist in 10 years

Its not obsolete yet. Having a separate PDAF sensor and processor gives you faster AF. With on sensor PDAF the image processor has to do everything. One reason mirrorless bodies are a typically slower than OVF bodies is that the image processor has to handle the AF, metering, focus & tracking, WB, & EVF. They are require a lot of horsepower and that sucks battery life. The new Samsung NX-1 is the first of the next generation of camera that will have massive processing power. It's possible that Sony can take SLT to the next level and make it a viable platform. The 24-70 F/2.8 Zeiss with new AF motor is set to be announced in the next few weeks and it will work with the Sony AF-D mode which has a lot of potential.

[rawr]

Just for info, a related Pentax patent from 2007. But it seems everyone - Panasonic, Nikon etc - has patents on this sort of stuff.

[kadajawi]

Just for info, a related Pentax patent from 2007. But it seems everyone - Panasonic, Nikon etc - has patents on this sort of stuff.

Do I get that right? A focusing screen that is also a display? And the display needs to be self illuminated? I think the main problem is such a display doesn't exist. OLED displays that are transparent aren't fully transparent. Plenty of light is getting lost, making it useless for this application.

[rawr]

OLED displays that are transparent aren't fully transparent. Plenty of light is getting lost

That's the basic problem with any 'super OVF' with EVF elements. Essentially they need to merge two viewscreens (digital and optical) without any IQ or other compromises. No one has got it completely right yet, I think.