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Plug that hole!


Ags
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DSLRs are better than CCDs in many ways, but one often overlooked advantage they have is they have an extra hole to let in more light! This hole, known as a viewfinder, is usually used to help frame your pictures in daylight photography, but at night it comes into its own, helping to brighten your low-light images.

Here is a picture taken in broad daylight with the lens cap on and the viewfinder inadvertently blocked by my thumb (1100D, 30 seconds, ISO6400); look how dark the image is:

GyjcLMj.jpg

After remembering to remove my thumb from the viewfinder, look how much brighter and more detailed the image is:

tXpTVHw.jpg

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Wait, what?

As a photographer (The regular kind) I can say that's not how DSLRs work. When you're looking through the eyepeice/viewfinder, that's because a diagonal is blovking the light going to the CMOS/CCD and reflecting it upwards to the viewfinder. To take images trhe viewfinder is blocked and the CMOS/CCD is allowed to absorb the light.

Unless you're using some funky two-lensed DSLR, I don't know how your image got so much brighter.

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I'm aware that the mirror rests against a light seal, but Canon provide a viewfinder plug on the strap for a reason.

This is an extreme example - a crazy ISO in bright sunlight. I don't know how relevant this is under astronomical conditions.

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I'm aware that the mirror rests against a light seal, but Canon provide a viewfinder plug on the strap for a reason.

This is an extreme example - a crazy ISO in bright sunlight. I don't know how relevant this is under astronomical conditions.

Me too.

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Wait, what?

As a photographer (The regular kind) I can say that's not how DSLRs work. When you're looking through the eyepeice/viewfinder, that's because a diagonal is blovking the light going to the CMOS/CCD and reflecting it upwards to the viewfinder. To take images trhe viewfinder is blocked and the CMOS/CCD is allowed to absorb the light.

Unless you're using some funky two-lensed DSLR, I don't know how your image got so much brighter.

I can only guess that as a photographer (the regular kind) that the objects you photograph will not be effected by small amounts of light leakage. AP is about as far from regular photography as sailing is to speedboating :D

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I can only guess that as a photographer (the regular kind) that the objects you photograph will not be effected by small amounts of light leakage. AP is about as far from regular photography as sailing is to speedboating :D

I don't know what others do, but when imaging I make every effort to elinate light sources around the scope and camera. The chances of enough light getting past the light seal are remote at best.

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I don't know what others do, but when imaging I make every effort to elinate light sources around the scope and camera. The chances of enough light getting past the light seal are remote at best.

and yet it happens, still, I won't begin to tell you how to do your ap. its all about personal choice and you seem happy enough

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I now rest my black tablet case over my camera when taking dark frames because I found that they came out proper dark if I do this. Have a street light nearby must have been creating enough light to get in the viewfinder.

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I had my mirror on my D5100 out 6 months back, and was careful to align it well going back in. Interesting that as conservative as Nikon is, that they don't seem to think a rubber cover is needed. I've taken plenty of darks at ISO up to 1200 and 3 minutes. I've seen no sign of light leakage. Better seal? It does appear that the OPs mirror isn't seating properly as the light has a bit of gradient. If you need the plug, use it.

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Canon do the same. They also recommend blocking 5he viewfinder for daytime photography if you are using a tripod and remote shutter release.

In normal use the viewfinder is blanked off when the user holds the camera to the eye.

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Canon do the same. They also recommend blocking 5he viewfinder for daytime photography if you are using a tripod and remote shutter release.

In normal use the viewfinder is blanked off when the user holds the camera to the eye.

In the daytime the light coming through the viewfinder throws the metering off - I forgot to put the shield in place for the transit of Venus  :iamwithstupid:  so all my pictures were underexposed. Can we go back and do that again, please?  :angry7:

Edited by Adrian
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On a similar note I found a laptop near the base of the scope made for bad AP, eventually figured out even the night vision colour setting in carte du ciel was bright and close enough to cause poor images. Ended up getting a 3m usb cable and keep the laptop as far away from the scope as possible

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My upstairs neighbour's kitchen downlights have no such easy solution. And here in Holland, people don't believe in curtains.

My house is very guilty of contributing to LP. I have a skylight window that exists to let light in during the day (My stairs got really dull looking without it) But at night... well... it's like the bat signal.

And there are two rooms at the back of my house that either have very bad curtains or nothing at all.

*Sigh* I guess I could deal with the rooms... But the skylight would be impossible to block just for night time...

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