[BarryE]

I've got into a lazy habit of using mirror lockup and remote, but forgetting to mask the lens while the mirror is flipped up.

I used to flip the mirror up and hold my hand over the lens before removing my hand and taking the shot. The idea is that the sensor is exposed during MUP, so if the sun was in the frame I could be waiting a few seconds for conditions to unfold before firing the shutter, thus exposing the sensor to the sun. Somehow, I fail to do this hand trick any more. So the question ... Anyone got a view (yes, I know it's unlikely ), if the sensor is ever likely to really be damaged in these circumstances. Obviously, if it was a full sun then there well might be an issue, but let's say a setting sun ...?

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Last edited by BarryE; 10-19-2018 at 08:42 AM.

[Tranzistors]

I depends on your lens. If you have a 20mm f/5.6, it might not damage the sensor. If the sun is out of focus, it can help a lot too. Sunset might give you 3 stops, but a fast lens could still manage to hurt the sensor.

Disclaimer: I do not speak from my own experience.

[pschlute]

From my experience with the K1 and troubleshooting shutter shock, I would suggest that MLU is unnecessary with the K1 at any shutter speed.

You are more likely to get shutter shock in the 1/60-1/200 range when using a tripod and only then when using long lenses with a foot attachment.

[photoptimist]

First, are you sure MUP exposes the sensor? On some cameras, MUP raises the mirror but it does not open the shutter.

Second, a bit of math shows that a lens with an aperture of f/107 makes a focused image of the sun that is as intense as normal sunlight. That's only pleasantly warming and of no danger. But that same math shows that an f/2.8 lens makes a focused image of the sun that is 1,460 times as intense as normal sunlight. That's more than enough to fry ants or sensors.

Third, there are examples on the internet of people who have permanently burned spots on their shutter, mirror box internals, or sensor. Most of these involved long-focal length lenses in the context of last year's solar eclipse. Long-focal length lenses gather a lot more light which makes them much more likely to create damage. But I've seen at least one case of permanent sensor damage that happened with a wide angle lens (IIRC it was 18mm on a Sony mirrorless) to someone doing landscape shots. They had the camera on a tripod so the tiny image of the sun fell on the same spot on the sensor for some minutes.

Finally, the setting sun certainly is less bright but exactly how much less bright is a strong function of altitude, humidity, dust, etc. as well as time til sunset. Here in Colorado, the sun can be extremely intense even when the sun's disk is still touching the horizon. But at the seaside, humidity and spray strongly attenuate the light. You can safely estimate the attenuation of the setting sun by spot-metering a sunlit gray card (or the palm of your hand) and comparing the result to the sunny f/16 rule. In full sun the reading should be something like 1/100 sec, f/16, @ ISO 100. If the setting sunlight reading is down to 1/4 sec, f/16, @ ISO 100, then you know the sun is 1/25 of it's normal brightness which might be safe (or at least safer). Or, you can less safely check by hand-holding your lens in front of your other hand, carefully focusing the sun on your skin and seeing if it hurts!

[pschlute]

First, are you sure MUP exposes the sensor?

I overlooked this point when first reading the OP post. MLU only flips the mirror up when you press the shutter/remote and you have to press again for the shutter to open/close.

The sensor is only exposed continuously in LV mode

[BarryE]

I'm a little confused. When using the optical viewfinder, ie not LV. The remote flips the mirror up. Vibrations settle (I do need to wait in my experience). I wait for a few seconds for things to settle, clouds to move etc then I press the remote to fire the shutter. Somehow I had thought during the period the mirror was locked up the sensor was exposed. I'd forgotten this perceived risk and ceased to protect the sensor with my hand. So is there no risk if *not* using LV, as I don't ? So I was wasting my time with all the hand stuff ???

What got me thinking was that I'm running a workshop tomorrow and I came across the following in my client's Canon handbook as I was familiarising myself with her camera. The handbook warns that when mirror lockup is stablized take picture promptly in bright light (defined as artificial light, sun, snow) as it may damage the sensor. So Canon do this function differently ?

[funktionsfrei]

It is possible to damage the shutter with too much sunlight, so MLU isn't the best thing to do when pointing the camera directly at the unfiltered sun. Even the iris inside your lenses can be ruined.


See here: Lens Rentals | Blog

[Digitalis]

It is possible to damage the shutter with too much sunlight

It is possible. Historically Rangefinder photographers who were careless enough to point their camera to the skies would get a lovely scorch mark or complete burn through of the cloth-rubber shutter. This is yet another reason why lens hoods were considered an essential accessory on early RF cameras.


Metal bladed / composite material shutter curtains like the ones used in the Pentax K-1 are much more durable than the shutters of older cameras, but they still warrant careful maintenance.

The handbook warns that when mirror lockup is stablized take picture promptly in bright light (defined as artificial light, sun, snow) as it may damage the sensor. So Canon do this function differently ?

No, they don't. Canon just mentions this to protect themselves from liability, It's called boilerplate. And in any case the sensor itself is protected by the sensor filter stack which includes a UV/IR blocking filter which varies in strength from manufacturer to manufacturer - It is designed to attenuate the blatantly destructive frequencies of light from the sun. The chances of completely bleaching the Bayer CFA* from sunlight exposure is remote. but I have to say that would be a safer way of converting your camera to monochrome**.


* Colour Filter Array
** Currently the only way to do this is to mechanically abrade the CFA off the sensor die - needless to say this will utterly void the warranty and potentially damage the sensor. So perhaps strapping your camera to a synchotron - the only problem I see with this is bombarding a sensor with so many photons will undoubtedly generate a considerable charge that will have to be shunted away before it can reach levels that could damage the onboard electronics.