[mst]

I just stumpled across the rumored specs of the (maybe) upcoming Sona a33 and a55 cameras, which are said do be pellicle cameras.



Which made me wonder: would it be possible to build a more compact digital camera for existing lenses by using a fixed mirror and moving the sensor and shutter (if still required) to where the viewfinder screen currently is? A high quality EVF could replace the actual viewfinder.



Could look like a normal camera, but would be slimmer, while still using existing glass.



Comments?



-- Markus

[Klaus]

[quote name='mst' timestamp='1282152495' post='1882']

I just stumpled across the rumored specs of the (maybe) upcoming Sona a33 and a55 cameras, which are said do be pellicle cameras.



Which made me wonder: would it be possible to build a more compact digital camera for existing lenses by using a fixed mirror and moving the sensor and shutter (if still required) to where the viewfinder screen currently is? A high quality EVF could replace the actual viewfinder.



Could look like a normal camera, but would be slimmer, while still using existing glass.



Comments?



-- Markus

[/quote]



The only value add would be the phase detection AF. I reckon many users can live without anyway.

[mst]

[quote name='Klaus' timestamp='1282153603' post='1885']

The only value add would be the phase detection AF. I reckon many users can live without anyway.

[/quote]



Hm, why not place micro phase detection AF sensors right into the image sensor? What works for compact cameras might work for DSLR size cameras, too.



-- Markus

[edge]

[quote name='mst' timestamp='1282154061' post='1887']

Hm, why not place micro phase detection AF sensors right into the image sensor? What works for compact cameras might work for DSLR size cameras, too.



-- Markus

[/quote]



I thought your idea was to make a camera capable of use existing lenses on a thinner system (use the mirror to move the distance requirement from lens to sensor from a horizontal one to a vertical one).

[Brightcolours]

[quote name='mst' timestamp='1282152495' post='1882']

I just stumpled across the rumored specs of the (maybe) upcoming Sona a33 and a55 cameras, which are said do be pellicle cameras.



Which made me wonder: would it be possible to build a more compact digital camera for existing lenses by using a fixed mirror and moving the sensor and shutter (if still required) to where the viewfinder screen currently is? A high quality EVF could replace the actual viewfinder.



Could look like a normal camera, but would be slimmer, while still using existing glass.



Comments?



-- Markus

[/quote]

The only gain you will make is the tickness of the board containing the image sensor, + sensor. The board containing the sensor has to be a bit wider than the sensor though, so how much less thick the camera can be will not be all that much.



You will have to have an EVF using the image sensor, though. That means using the image sensor continuously. Which means heat problems. And a reduced battery time.



Problem with EVF's: They suck. They lack the 3D look into the scene you get with a real viewfinder, and are a pain in certain light conditions too. And say farewell to exchangeable focus screens.



Problem with a pellicle mirror: AF sensor can not be housed in the bottom anymore.

So, AF needs to move up.

Oops, the sensor will be there. So AF will have to be done via image sensor. So... either slow contrast AF, or hoping a solution like the new Fuji patent on PD AF photo diodes on the image sensor actually can work precise and with low light.

Photodiodes are very small, though...



So you gain (lose) 2mm of camera thickness and permanent mirror lock up. In exchange you get a sucky EVF and possibly AF in its place, heat issues with the bigger sensors, no MF focus screen possibility, a hell of a time trying to clean the sensor. And metering has to be done evaluating the image data of course, but that should not have to be a minus.



And you should hope the camera system has in-lens IS, because in-body IS will make the needed sensor space a lot bigger.

[mst]

[quote name='edge' timestamp='1282154364' post='1889']

I thought your idea was to make a camera capable of use existing lenses on a thinner system (use the mirror to move the distance requirement from lens to sensor from a horizontal one to a vertical one).

[/quote]



Yep. However, a hybrid AF system, as it has been introduced by Fujifilm with the F300EXR for example, could help to further reduce the body size.



If you rely on classic phase detection, you'd need a secondary mirror and the AF sensors themselves (probably on the other side of the sensor, in the bottom of the camera). Putting the AF sensors right into the image sensor would allow for a mechanically more simple solution, while on the other hand offering the potential to increase the precision of the AF, because the sensors are right where the image is.



The question is, if the precision of Fuji's solution is sufficient for DSLRs. The sensor base might be too small for this, but I guess this could be worked out.



-- Markus

[mst]

[quote name='Brightcolours' timestamp='1282155590' post='1891']

So you gain (lose) 2mm of camera thickness and permanent mirror lock up.[/quote]



I guess it's quite a bit more than just 2 mm. The sensor does not start exactly where the mirror ends today, there's some space, the shutter, then the sensor and some electronics and finally some amount of body/case material.



The sensor plane is marked on both the D3x and the D200 (sorry, not much else here to check), it's roughly 2 cm from the sensor plane to the back of the camera with the D3x and still around 1 cm with the D200.



I agree, though, there's not too much space to gain, yes. Plus, of course the size of the lenses would remain unchanged. But they all would fit.





[quote name='Brightcolours' timestamp='1282155590' post='1891']

In exchange you get a sucky EVF and possibly AF in its place, heat issues with the bigger sensors, no MF focus screen possibility, a hell of a time trying to clean the sensor. And metering has to be done evaluating the image data of course, but that should not have to be a minus. [/quote]



I think EVFs will improve vastly over the next few years. That's probably the next big thing.



With a good EVF, a MF screen would no longer be required. And metering works pretty well on all micro cameras, at least on the G1 I own. Heat is no issue here, either, at least for "normal" use. I don't use it for astro photography or several minutes exposures.



-- Markus

[Brightcolours]

[quote name='mst' timestamp='1282156322' post='1893']

I guess it's quite a bit more than just 2 mm. The sensor does not start exactly where the mirror ends today, there's some space, the shutter, then the sensor and some electronics and finally some amount of body/case material.



The sensor plane is marked on both the D3x and the D200 (sorry, not much else here to check), it's roughly 2 cm from the sensor plane to the back of the camera with the D3x and still around 1 cm with the D200.



I agree, though, there's not too much space to gain, yes. Plus, of course the size of the lenses would remain unchanged. But they all would fit.









I think EVFs will improve vastly over the next few years. That's probably the next big thing.



With a good EVF, a MF screen would no longer be required. And metering works pretty well on all micro cameras, at least on the G1 I own. Heat is no issue here, either, at least for "normal" use. I don't use it for astro photography or several minutes exposures.



-- Markus

[/quote]

The G1 has a small sensor though... the biggest heat issues can currently be seen with the Nikon full frame cameras, which have 4x the sensor size.

But also the APS-C cameras from Nikon and Canon have limited duration of live view and video due to heat generation.

[popo]

[quote name='Brightcolours' timestamp='1282155590' post='1891']

Problem with a pellicle mirror: AF sensor can not be housed in the bottom anymore.

So, AF needs to move up.

Oops, the sensor will be there. So AF will have to be done via image sensor.[/quote]

The Sony method is believed to use the mirror for providing phase AF, with no OVF. EVF via main sensor only.

a hell of a time trying to clean the sensor.

If the mirror really is fixed, the sensor could be in a sealed chamber where dust can't get inside in the 1st place. If the mirror can still flip, you could reach it as normal. However you do need to worry about cleaning the mirror if it is fixed, but at least it is far from the focal plane so any dust on it would become visible less easily.

[Brightcolours]

[quote name='popo' timestamp='1282157038' post='1895']

The Sony method is believed to use the mirror for providing phase AF, with no OVF. EVF via main sensor only.





If the mirror really is fixed, the sensor could be in a sealed chamber where dust can't get inside in the 1st place. If the mirror can still flip, you could reach it as normal. However you do need to worry about cleaning the mirror if it is fixed, but at least it is far from the focal plane so any dust on it would become visible less easily.

[/quote]

The sensor on top can't be in a sealed chamber...