The benefit of the caddy idea would be to make the mirrors easily swappable. It is a pipe dream, and I'll likely end up with a more permanent method as you describe and then just have a second 5D for AF usage.
gasrocks wrote:
Why is the mirror not 100% reflective to begin with? What does the amount of light going through it do?
40% of the light goes through the mirror, hits a 100% reflective sub-mirror (set at an opposite angle) and bounces down to the AF sensors in the bottom of the mirror-box.
OK, thanks. I guess I thought AF sensors were up in the viewfinder along with everything else. How is AF done during LiveView with the mirror up? Aren't they working on cameras that will have no mirror at all?
gasrocks wrote:
OK, thanks. I guess I thought AF sensors were up in the viewfinder along with everything else. How is AF done during LiveView with the mirror up? Aren't they working on cameras that will have no mirror at all?
AF in LiveView is done via contrast detection off the imaging sensor feed rather than using the phase-detection hardware that's used by the camera in normal use (With the exception of Sony cameras, which use a sensor in the viewfinder to provide the Live View feed and allow use of the normal AF system at the same time). A few cameras can also interrupt the LV feed to flip down the mirror and use the normal AF system.
gasrocks wrote:
OK, thanks. I guess I thought AF sensors were up in the viewfinder along with everything else. How is AF done during LiveView with the mirror up? Aren't they working on cameras that will have no mirror at all?
LiveView AF is done on the imaging sensor itself, with what is called "contrast detect AF".
I can only assume that any new mirrorless camera designs will use contrast detect AF on the imaging sensor.
But, probably enough to restore the brightness of the Ee-S to that of the stock screen, no?
It isn't that I have an issue with my VF or my screen, it's just that I'm more than willing to throw AF out the window for an even better VF experience.
The amount of light increase in the viewfinder - going from 60% of available light to 100% of available light is 2/3 stop. Going from 50% available light to 100% available light would be 1 stop.
I think there is some merit to the project. Buuuuutttt, unless you find a really good replacement mirror I think the gains will be outweighed by the problems. You need a mirror that has a thickness and weight that is very close to the original.
The thickness is more critical that the weight. You have very few adjustments and those have very small leeway. If you fall too far outside the existing tolerances, you may not have the adjustment range to make it work.
In weight, I think the current mirrors are much lighter than older mirrors so the strength of the mechanism has been reduced.
Unfortunately, since most cameras are now autofocus you can't just take the part from another model and adapt it,
The mylar idea may be the best if you glued it to the existing mirror. Maybe you don't have to glue it - companies that add a tinted film to car windows - I think they just use a water film to adhere. If you end up having to get your mirror replaced, I have read that Canon will replace the entire mirror box, at some expense.
I don't think the mirror was meant to be removed. Since it is glued in place I doubt it can be removed without damaging the mechanism. If it falls off, it could be attached again.
I hope this does not sound too negative. Every time you get an idea you have to go through the pros and cons.
Yeah, I'm going to explore the mylar idea a bit more. I think I found some material that will be well-suited to the task and it seems it does not require any adhesive, so it can be removed without any residue and replaced at will.
I've contacted the supplier of this product for more info. Fingers are crossed.
I have some completely chrome adhesive vinyl here, it's very very thin and the adhesive leaves no residue. I've applied it to really smoothe surfaces before and it goes pretty flat but there's a small chance it might get a little motley. Perhaps I should be brave and try it. A brighter viewfinder isn't much use if it isn't uniform
thrice wrote:
I have some completely chrome adhesive vinyl here, it's very very thin and the adhesive leaves no residue. I've applied it to really smoothe surfaces before and it goes pretty flat but there's a small chance it might get a little motley. Perhaps I should be brave and try it. A brighter viewfinder isn't much use if it isn't uniform
Daniel Heineck wrote:
FWIW, this will COMPLETELY screw up your auto-exposure as well... since its calculating based on the 2/3 of a stop loss.
D
Yes, I've considered this on page 1. I have to chimp and use EC anyway due to the stop-down metering issues with manual lenses. Maybe it'll just all balance out...
Otherwise, maybe we'll just have to find out how to tweak the firmware and add a c.func. for "100% mirror".
robsteve wrote:
Your problem may not be the mirror, but the penta-prism. One of the better SLR viewfinders is the Leicaflex SL and that camera also used a partially silvered meter.
Robert
Only the central area of the SL's mirror is partially silvered and wouldn't be surprised if that region reflects more than 60% of the light to the viewscreen.
Cogitech: Metallized polyester is very commonly used in food-packaging as O2-barrier, usually in formats of 12+0.2um (PET-Al) before lamination with heavier printed material. Call any packaging/printing company or DuPont materials directly and explain your experiment, and they will probably send you a couple of square feet for free... You can try it riskfree, as you can "glue" it to the mirror semi-permanently by using a VERY small amount of ordinary cooking oil or clear mineral oil. I'd try putting the Al side against the original mirror, this would make the focus adjustments almost zero... Or make that 1/2micron+the filmthickness of oil... (I'm supposing that Canon also use "first-surface mirrors")
Another possible source of material is any normal "hobby-materials-shop". Try something like "silver cellophane" or a similar product name.
You'll need to find some very special mylar to match the reflectivity and flatness of an aluminum front surface mirror (approaching 95% in a full coating, and for all intents and purposes as flat as the underlying glass). But if you can get the mirror out of the camera, it's cheap and easy to have it resilvered (realuminized). Pretty much any place that refurbishes telescopes will be amenable to doing it for you. The ultimate would be a dielectric coating, which can have above 98% reflectivity. You wouldn't be able to tell the difference visually, though, and only special labs can grow it.
This sounds like a project where it'd pay to have an in at a repair facility. Ideally you'd pick up a body that had stared into the sun too long to start with.
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