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Viewfinder question?


JB80
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OK, this may seem a silly noobish question because it is but my old Canon 20D will not allow me to use the LCD screen as a viewfinder and I was wondering how that is going to effect things when i start to use it with my telescope? I guess it's not the biggest issue in the world(I hope) and to be fair I don't know if it is the same with newer camera's or not but it would seem like it would add more issues than it would solve, like focusing and such.

So basically is this going to be an issue for me or am I worried about nothing?

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Not at all IMHO. Live view is next to useless because of the low sensitivity and the poor resolution of the preview screen (compared with the normal use of the sensor). Running live view also raises the temperature of the sensor substantially, which causes extra noise (dark current doubles with every 7C rise in working temperature).

The better cameras have provision for changing the coarse focusing screen in the optical viewfinder for a much finer one, used in conjunction with a magnifying angle finder you can focus much more accurately than you can with the preview screen.

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The better cameras have provision for changing the coarse focusing screen in the optical viewfinder for a much finer one, used in conjunction with a magnifying angle finder you can focus much more accurately than you can with the preview screen.

Ahh, yes of course. I totally forgot that I had read about before, that actually helped me a lot, thanks.

I'm just trying to get my head around the camera before my parts come and I guess just wanting it all right now and not having it I managed to get myself into a mini panic.

Magnifying Angle Finder is added to the list:D

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I would say that both viewfinder (with or without angle finder) and live view are both only useful when there is a bright object in the frame.

When there is a bright object then I find live view very useful for focusing. Without it I think I would have to do small adjustments, test shots and review on the screen (and zoom in). I usually focus on a planet or bright star using live view before finding my intended target.

When I am framing my actual photograph I always do test shots. Sometimes the targets are faint enough that they only show in a longer exposure at maximum ISO. I recently had to do 1 minute test shots just to find and frame the target.

In summary, I would say live view is very useful for focusing but you can get by without it. I think it's also true that the newer high resolution LCD screens on the later cameras make live view even more effective, since you can judge focus more precisely.

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  • 3 weeks later...

Hello, I'm thinking of getting a DSLR soon and I've been thinking about this viewfinder issue for a while.

Assuming I'm doing prime-focus photography I figure I'll have to solely use the live view to set up the shot - won't the view through the normal viewfinder be a complete blur, even when the image on the sensor is in focus?

Or am I worrying too much? :o

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Ah really, good stuff - that's one less worry. I'm slightly tempted to get a camera that was cheaper as a result of its lack of live view...is that a bad move? I could always take a snap and then zoom in, to check the focus? Or should I just spend the cash?

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Bang per buck the older 300D and 350D cameras are very good value.

Throw in an angle magnifier viewer and they will satisfy you for a long time.

You just have to look at the excellent images obtained with them to realise the more modern cameras may have more "bells and whistles" but old is still good.

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the more modern cameras may have more "bells and whistles" but old is still good.

In fact the high pixel count of modern cameras counts against them ... much more of an issue with noise; and the noise reduction software built in to cope with this (plus the ludicrous ISO settings that newer cameras tend to have) does no favours at all for astro imaging.

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In fact the high pixel count of modern cameras counts against them ... much more of an issue with noise; and the noise reduction software built in to cope with this (plus the ludicrous ISO settings that newer cameras tend to have) does no favours at all for astro imaging.
The noise issue - is that because the pixels are smaller (assuming the sensor is no larger)?

And the ISO setting thing - surely the user can just turn down the ISO setting on the camera? Or does the fact that the sensor supports a high ISO setting kind of introduce noise to the lower ISO settings?

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The noise issue - is that because the pixels are smaller (assuming the sensor is no larger)?

And the ISO setting thing - surely the user can just turn down the ISO setting on the camera? Or does the fact that the sensor supports a high ISO setting kind of introduce noise to the lower ISO settings?

Yes - smaller individual pixels mean lower photon counts, which increases noise.

You can indeed turn the ISO setting down and this is the best thing to do. All the ISO setting does is multiply the electron counts in the sensor wells, you're not actually gaining sensitivity ... modern DSLR sensors have a native ISO rating of 100-200 (smaller for denser arrays) and this is the sensible setting to use them at.

Compact cameras with very high pixel counts (> 10 MP) actually have such small individual sensors that the native ISO rating is around 10. The slowest available setting is usually around 100 ...

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My preference is always to use live view for focusing rather than the optical finder, I've been using DSLRs for a number of years for astrophotography and I was always getting focus problems with a 20D and a 5D because of the tolerance of the focusing screen positioning. I find with the Canon 550D I use now I can get focus quite easily on stars down to about mag 5 and with 10x magnification on the high resolution screen you're viewing at better than 1:1 pixels. The noise issue is certainly getting better every generation of camera as well, I can quite happily shoot at 1600 iso on the 18mp 550D with lower noise than I used to get at 800 iso on the 8mp 20D, it's pointless using anything lower than 800 iso as stacking will soon smooth out the noise.

Mel

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