"mirrorless" with optical viewfinder

[Pawel Achtel]

Good post Jeff. Totally agree.

Here is my 2 South Pacific Peso (a.k.a. Australian cents at current exchange rate):

It is quite common that users, instead of giving Requirements, try to give Solutions. That's not productive because they usually have NFI about technology, physics or inner works of the camera.

An optical viewfiner is a Solution. It's not up to you to provide one. Instead, you should formulate your Problem or Requirement.

Red is not interested in Solutions. They have far better experts and capability than an average film maker.

What they like to hear are Requirements: the actual problems that you are trying to fix. For example:

I would like to be able to focus accurately to a single pixel using naked eye at 1 lux of ilumination.

or

It is mandatory that I be able to focus without power.

Then, of course, there is a matter of prioritising requirements and sorting valid onece from invalid or poorly defined.

[Lee Jay]

1. Focus. Since the critical relationship of lens to sensor plane is the primary determiner of focus, why introduce a physical mechanism that disrupts the pathway that light needs to travel to hit the picture plane?

Because phase-detection autofocus is so vastly superior to contrast-detection autofocus. And PD requires a mirror. That's why.

You are only introducing opportunities for the lens/sensor relationship to be compromised. Mirrors, spinning, fixed or otherwise moving will introduce vibration, possible loss of registration over time (heavy usage) or cause refractive artifacting that will affect image quality (fixed mirror/ beam splitter).

Indeed, that's the price to be paid for autofocus that actually gets the job done.

If we know for certain that an analog optical pathway to viewfinder will ultimately fail, why even bother to design it in? Why add the cost? Why needlessly bulk up the camera? Why would you intentionally shut off the instant feedback loop that the sensor provides you in order to judge focus, when that is the only critical focus information that means anything?

Because it's not needless. The zero latency, zero power usage, high resolution, and enabling of PD AF make it well worthwhile. You're exaggerating the difficulty here too - we now have a zillion *very* inexpensive dSLRs that have a mirror, an OVF, a secondary mirror and a PD AF system included in a camera that also has a pretty big sensor and all processing technology. If that system was so expensive, bulky, and difficult to produce, we would not have $500 camera bodies that include it. But we do.

Lee Jay

[reality]

Mechanical still camera shutters are not acceptable for a motion camera though as they will wear out very quickly.

A spinning shutter would be too bulky and too limiting for framerates/stills. They also have a limited life.

[Dan Hudgins]

Mechanical still camera shutters are not acceptable for a motion camera though as they will wear out very quickly.

A spinning shutter would be too bulky and too limiting for framerates/stills. They also have a limited life.

Not sure if this has been gone into but I had an idea for an optical finder that might work,

You make small holes near each pixel on the sensor that go through the dark parts to a clear base or all the way through the sensor chip, you can then view through the back of the sensor.

Yes there would be some light loss, but you get 100% duty cycle, and because the holes are always in the image plane you compensate for the OLPF focus shift issues and such to get true focus without any shifts in the optical finder. The small size of the holes make the focus more accurate and you can use a field lens to focus the light that goes through the holes into your eye piece.

So the sensor would be like a piece of "peg board" with viewing from its backside. You would not see the grid because at 4K the pitch is too small to see clearly with a full view optical viewfinder, at 2X zoom you might see the grid a little if you have good eyes, but that would be a help to focus the eyepiece on.

[Pawel Achtel]

Because phase-detection autofocus is so vastly superior to contrast-detection autofocus. And PD requires a mirror. That's why.

No, DP does not need a mirror. DP needs to focus accurately. And this is big difference.

[Dan Hudgins]

No, DP does not need a mirror. DP needs to focus accurately. And this is big difference.

No matter what kind of optical finder a camera uses, it can be very hard to focus well with the lens stopped down through the eyepiece with a ground glass.

My Brother says that DP for the most part should not focus through the eyepiece while the camera is running, anyone have thoughts on that subject?

What he means is that the follow focus is used for focus and the optical finder is used for framing while the camera is running, if that is the case then you should not need an optical finder for framing if you have an electronic one.

If the optical finder is just used to mark the follow focus when the camera is stopped, then you can make a rack over camera with optical finder like the Mitchell, that lets you view the image to focus and then use the electronic finder for framing with the lens stopped down since you cannot see much in an optical finder at f/22 anyway.

A rackover has problems since the OLPF on the sensor may change the focus point for fast lenses, so it is better to use a 1:1 electronic finder to find the follow focus marks anyway.

For documentary/sports use a reflex optical finder could be useful, maybe someone could make a PL mount optical finder with relay optics that would let you use any PL mount lens on any PL mount camera, and have a 10% or 50% tap off optical finder as an accessory since you would not need the optical finder all the time?

[Lee Jay]

I'll disagree with your wording... it is a bit more complicated/interesting than that but will wait to explain until after we announce.

Jim

Okay, I'm awaiting an explanation. From the specs, it looks like neither Scarlet nor Epic compete in the dSLR space.