# Darkening OVF without power



## trof2 (Dec 24, 2013)

I just noticed an interesting phenomenon with my 70D. Whenever there is no battery in the camera, the optical viewfinder becomes blurry and a couple stops darker.

At first I thought the lens stops down and loses focus without power, then quickly rejected that idea because no lens works that way, and the ovf is darkened even without a lens attached.

I am now rather curious about the two questions at hand:
1. What mechanism makes the ovf lose focus in the absence of power? I was not aware there were any focusing components in the system.
2. What in the world would darken the image without power? Perhaps some reverse electrochromic layer that is necessary for the lcd overlay to work, but then why would they lighten 95% of the display with power, rather than just darken the 5%, like the standard lcd overlays?


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## jrista (Dec 24, 2013)

trof2 said:


> I just noticed an interesting phenomenon with my 70D. Whenever there is no battery in the camera, the optical viewfinder becomes blurry and a couple stops darker.
> 
> At first I thought the lens stops down and loses focus without power, then quickly rejected that idea because no lens works that way, and the ovf is darkened even without a lens attached.
> 
> ...



Any chance you could take a photo with another camera through the viewfinder of your 70D to show the effect?


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## neuroanatomist (Dec 24, 2013)

jrista said:


> Any chance you could take a photo with another camera through the viewfinder of your 70D to show the effect?



So you're saying you want the OP to provide you with evidence, when you could just RTFM?  

The dark VF with the battery removed is mentioned on p.34 of the 1D X manual and on p.30 of the 5DIII manual. I don't have the 70D manual handy, but I'm sure it's in there...

Presumably the liquid crystal used in Canon's implementation of the transmissive LCD requires power to remain clear, no power means dark and blurry, due to disorganization of the molecular structure of the liquid crystal. It is the opposite of normal transmissive LCDs, where unpowered pixels pass light, but could possibly result from the orientation of the either the bottom or top polarizer of the LCD being rotated 90° from the usual orientation.


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## jrista (Dec 24, 2013)

neuroanatomist said:


> jrista said:
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> > Any chance you could take a photo with another camera through the viewfinder of your 70D to show the effect?
> ...



Well, having never read the manual, seeing as I don't have it, yes, I'd like evidence.


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## neuroanatomist (Dec 24, 2013)

jrista said:


> neuroanatomist said:
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Fair enough. You have a 7D, it has a transmissive LCD. You could always try your 7D's manual (if you have one...if not, and your Google finger is broken, maybe someone can help you out with a link  ), the same statement is on p.26. I suppose you could even try pulling the LP-E6 out of your powered-off 7D while looking through the VF, depending on how badly you want evidence, and how likely you'd be to believe evidence from another for something which you can easily test yourself. The effect the OP mentions is pretty dramatic. There's a brief lag after pulling the battery before the VF goes darker and blurry, but trust me - you can't miss it. Well, unless you don't even try...


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## jrista (Dec 24, 2013)

neuroanatomist said:


> jrista said:
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The difference between you and I is you sound like you've experienced the issue. I haver have, as I don't generally spend my time looking through the viewfinder while I remove the battery (with my grip, I don't actually ever recall even having to change a battery in the field, and when I'm home, I'm never looking through the VF when I pull them out to charge.) So, all your snide comments aside, I think asking for a visual example of what sounded like a legitimate bug certainly seemed like a reasonable place to start.


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## neuroanatomist (Dec 24, 2013)

Experienced only because I do read the manual when I get a new camera, and Canon's description of what seemed odd behavior for a transmissive LCD piqued my curiosity (it's a scientist thing), and so I empirically tested it (also a scientist thing) to see for myself. 

Sorry for being snide, I was getting a bit tired. :-[


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## Sporgon (Dec 24, 2013)

On the subject of the translucence LCD, I wonder if this is the reason Canon don't support the Ec-S 'manual focus' screen in the 1Dx. 

Nikon were using these way before Canon and I hated them. In those days I was doing mostly manual focus and although the transmissive LCD gave a bright enough viewfinder it was not sharp. Changing to the Canon 5D (and before that very briefly a Pentax K7), was a revelation, once again getting the crisp, sharp viewfinder. 

If the transmissive LCD negates the Dof characteristics and benefit of the Ec-S screen I can understand why Canon do not give a custom setting for it. 

In the same way I would assume that a 'hybrid' EVF is likely to give a poorer quality OVF.


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## neuroanatomist (Dec 24, 2013)

Sporgon said:


> If the transmissive LCD negates the Dof characteristics and benefit of the Ec-S screen I can understand why Canon do not give a custom setting for it.



I don't think that's the case. I tried a borrowed Ec-S, the VF was brighter with a fast lens, and the 'focus snap' I saw with the Eg-S in my 5DII was there. Chuck Westfall indicated to me that Canon _could_ provide firmware support for the Ec-S, if they so choose.


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## trof2 (Dec 24, 2013)

jrista said:


> trof2 said:
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> > I just noticed an interesting phenomenon with my 70D. Whenever there is no battery in the camera, the optical viewfinder becomes blurry and a couple stops darker.
> ...



I'd have to buy a new lens for that shot


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## Sporgon (Dec 24, 2013)

neuroanatomist said:


> Sporgon said:
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> > If the transmissive LCD negates the Dof characteristics and benefit of the Ec-S screen I can understand why Canon do not give a custom setting for it.
> ...



That's good to know because it looks like the future of the OVF is going to include transmissive LCD of one form or another. 

Merry Christmas !


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## Mt Spokane Photography (Dec 24, 2013)

All the cameras with the transmissive lcd in the viewfinder do this, starting with the 7D several years ago. There is no workaround, you must turn the camera power on. Other items that require a powered up camera to work are the STM lenses whitch focus by wire.


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## neuroanatomist (Dec 24, 2013)

Mt Spokane Photography said:


> you must turn the camera power on.



Actually, you don't – the VF is bright as long as the battery is installed, even with the camera powered off. Which I suppose means that 'off' really isn't, which has implications for power drain while a camera with a transmissive LCD is sitting unused.


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## Mt Spokane Photography (Dec 24, 2013)

neuroanatomist said:


> Mt Spokane Photography said:
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You are right, I tried it with my 5D MK III. I seem to recall my 7D going dark when powered down, but its sold now.


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## Don Haines (Dec 24, 2013)

Mt Spokane Photography said:


> neuroanatomist said:
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Don't you guys have anything better to do with your time than pop batteries in and out of a camera to see if the VF darkens? 

BTW, it makes no difference on a 60D.....


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## neuroanatomist (Dec 24, 2013)

Don Haines said:


> BTW, it makes no difference on a 60D.....



It shouldn't, since the 60D doesn't have a transmissive LCD. I find the on-demand AF points, etc., to be a great feature.


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## Mt Spokane Photography (Dec 24, 2013)

Don Haines said:


> Mt Spokane Photography said:
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Nope, I have my camera right here by my computer, it took maybe 10 seconds to check it. I've already done my work for the day, its Christmas Eve here, so I'm taking it easy.


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