Lotusm50 wrote:
Why doesn't it make sense? Metal shutters certainly exist. A magnesium metal shutter could be lighter and stiffer than existing shutters. It would take less energy to move, can be made faster, could last longer, and would deform less in operation making it potentially more precise. Why not?
Most shutters are aluminium. The reason why it makes less sense is because one of the points you made is simply not true (I have boldened it).
Certain alloys might behave differently, but aren't cost effective for the very very minimal weight reduction.
Aluminium alloy 2014 has a maximum tensile strength of 483 MPa, whereas the strongest wrought Magnesium alloys have a tensile stregth of 305MPa.
I don't have figures for abrasion (shearing) or elastic modulus of magnesium alloys, but I'm sure a little googling would find these figures in favour of aluminium as well. Magnesium is lighter, but aluminium is sufficiently lighter than steel for electronic camera shutters.
thrice wrote:
Most shutters are aluminium. The reason why it makes less sense is because one of the points you made is simply not true (I have boldened it).
Certain alloys might behave differently, but aren't cost effective for the very very minimal weight reduction.
Aluminium alloy 2014 has a maximum tensile strength of 483 MPa, whereas the strongest wrought Magnesium alloys have a tensile stregth of 305MPa.
But tensile strength is not important for a shutter. It doesn't need tensile strength. It needs to be stiff and light, which is precisely where magnesium alloys have an advantage over aluminum alloys.
Young's Modulus is the important figure. It is the resistance to deformity (stiffness).
>60GPa for most alu alloys and 45GPa for magnesium alloys.
This is sufficiently off-topic I yeild to your higher knowledge of materials until I can speak to one of my mechatronic engineer friends (weird that I have more than one of those).
Alright I've been sufficiently put in my place by my friend, and a workable magnesium alloy shutter might be beneficial. Would cost them hundreds of thousands to develop and is interesting that they choose to put it in a DRF but he does say it's possible. I quote "There is no linear science when it comes to alloys" amongst a whole bunch of other physics speak. This is from my nanotech/astrophysicist friend.
With all the praise from Zeiss optics, I won't be surprise if this is indeed an RF camera that is made specifically for Zeiss............Contax G3 anyone??
douglasf13 wrote:
I think we're reading way too far into this shutter thing. Jeff probably just missed a comma in his tweet. Ie. Magnesium alloy, electronic shutter.
Not to mention, if it's an electronic shutter, it's not made of anything. The shutter happens on the sensor.
thrice wrote:
Young's Modulus is the important figure. It is the resistance to deformity (stiffness).
>60GPa for most alu alloys and 45GPa for magnesium alloys.
Or is it the shear modulus, or the bulk modulus? Or it is the ratio to material material density that is important? It's actually more complex than you seem to imply. It is not unreasonable to conclude that an Mg alloy part can be made to be lighter and stiffer than an aluminum alloy part. This is a well known Mg advantage. (note that you more likely design an Mg part differently than an Al alloy part, rather than just substitute materials without changing the design of the part). But there are a lot of things to consider that go well beyond a discussion here. For example, an Mg alloy shutter may also have better fatigue and cyclical loading properties, which could be very useful in a shutter.
douglasf13 wrote:
I think we're reading way too far into this shutter thing. Jeff probably just missed a comma in his tweet. Ie. Magnesium alloy, electronic shutter.
Not to mention, if it's an electronic shutter, it's not made of anything. The shutter happens on the sensor.
Lotus, et al.--If we're to keep running with the fantastical idea of a magnesium shutter, then allow me to butt in a little ;-)
IIRC Magnesium doesn't do as well as aluminum in corrosion nor in fatigue, and neither do as well as titanium or steel. The youngs modulus would be the material characteristic of most interest for this application, since pound for pound most high end metals are pretty close to the same yield strength. A properly done mag shutter would be lighter at the same thickness as an aluminum shutter and less stiff, or stiffer than an alu shutter at the same weight (due to stiffness following a r^4 dependence).
All in all, appropriate force analysis and an anisotropic material (e.g. boron/carbon fiber, aligned MMC's) aligned to the most relevant forces would probably be the best of all worlds as far as a shutter, but who knows. I don't know how much this would really improve the mechanism beyond a slightly higher sync speed.
What do companies use nowadays anyhow? Steel? Aluminum? Titanium? Okay--well the 1DIII used a combination of carbon and aluminum shutter blades.
Daniel
-A part-time nanoengineer nerd who's done a bit of bulk materials work.
Daniel Heineck wrote:
Lotus, et al.--If we're to keep running with the fantastical idea of a magnesium shutter, then allow me to butt in a little ;-)
IIRC Magnesium doesn't do as well as aluminum in corrosion nor in fatigue, and neither do as well as titanium or steel. The youngs modulus would be the material characteristic of most interest for this application, since pound for pound most high end metals are pretty close to the same yield strength. A properly done mag shutter would be lighter at the same thickness as an aluminum shutter and less stiff, or stiffer than an alu shutter at the same weight (due to stiffness following a r^4 dependence).
All in all, appropriate force analysis and an anisotropic material (e.g. boron/carbon fiber, aligned MMC's) aligned to the most relevant forces would probably be the best of all worlds as far as a shutter, but who knows. I don't know how much this would really improve the mechanism beyond a slightly higher sync speed. ...Show more →
zactly
high speed shutters are all about sync speed
and the real problem with magnesium would be attaching the curtains together with any reliability as curtains are not single, there are often 4
and anyway it looks like hes talking about a global shutter
1/4000 was the record in 1982 by Nikon FM2 with a carbon-reinforced Titan honeycomb shutter. Later production switched to a aluminum shutter.
1/8000 in 1988 by Nikon F801/N8008 (aluminum)
1/12000 in 1992 by Minolta 9xi (carbon fiber-reinforced epoxy)
I don't know... these camera makers have been working on shutters for half a century and I am sure they have secret recipes which could not be over-simplified to broad categories such as titanium, aluminum or carbon fiber.
Shutter blade mass momentum is the primary reason for the interest in high eng. spec materials for blades. Lighter moves faster, not hard to figure out...
I don't see the point of an autofocus rangefinder camera. The optical rangefinder is the best possible design for manual focus cameras, but for an autofocus camera contrast-detect AF using the imaging sensor makes way more sense to me.
Optical RF cameras require high precision mechanical coupling to the lens, and I don't think this design would be compatible with electronically driven focus motors in AF lenses.
If the camera does not have an optical rangefinder it should not be referred to as a "rangefinder camera"
