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Old Sep 2, 2006, 2:54 PM   #1
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OK, I have a few questions.

1. Why is mirror-lock-up so important to some? Canon people laugh at Nikon for not having MLU on some of their dSLRs. What is that good for? I know that Nikon has a feature where the mirror can be raised in order for the user to clean the sensor.

2. How exactly does a depth-of-field button work on a dSLR?

3. What exactly is Metering/Spot-Metering and what does it do?

Thanks for taking the time and clearing stuff out for me.

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Old Sep 2, 2006, 4:58 PM   #2
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Hey Zygh,
im not sure what mirror lock up is used for but DOF preview works like this (or at least on the cameras i know) It will stop down to the aperture you have selected and take a "preview pic" which is stored in the temporary bufer of the cAmera.

Now im not fully sure if im right about the next thing but if im wrong someone correct me:-)
Spot metering is where it takes a light reading from a really small "spot" in your picture, and then it averages your light levels on that.

As i said im not fully suire but i hope i have been at least partially helpful:-)
Happy shooting:|
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Old Sep 2, 2006, 7:20 PM   #3
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Mirror lockup is used when you want to be absolutely sure that the camera is steady druring an exposure. You would use mirror lockup with a cable/remote release to take the picture. This is most often used for time exposures where any movement of the camera, no matter how small, could degrade the picture quality.

The depth of field button on a dSLR, when pushed, will stop down the aperature of the lens to the set or picture taking aperature so that the photographer can visually inspect the depth of field in the optical viewfinder.

A spot meter will take it's meter reading from a very small spot on the subject, while normal metering will take an averaged or weighted reading from the entire scene in the viewfinder.

Hope that helps.
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Old Sep 3, 2006, 10:19 AM   #4
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Both are nice features, but most will never use them. DSLR viewfinders are typically too dark and small to use DOF preview properly. It's just as easy (if not easier) to just snap a preview image and use the LCD to detemine DOF. DOF does not save an image to the buffer for review as was mentioned in a previous post.

Mirror lock up does reduce vibrations from mirror slap, but unless you shooting longer exposures and using a tripod mirror lock up serves no practical purpose, and even when used you may not even notice a difference from usingthefeature at normal print sizes.
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Old Sep 3, 2006, 10:54 AM   #5
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I would generally agree with the definitions above, I just wanted to add a few comments.

For most people, mirror lockup is not useful. You just won't use it. But if you *do* care about mirror lockup you probably use it ... "every now and then". Not every not... not even every week. but you do use it. I've used it maybe 5 times in 4 years. One of those shots is on my "Favorites" list.

I fully agree with DOF preview as not being very useful in most cameras. I just couldn't see the difference with my 10D or 20D. When I upgraded to the 1D MkII N, which has a better view finder, I have used it and it has made a difference. I think its most useful with Macro, where the placement of the DOF is critical to success. At least, that is when I've used it. I rarely do macro (but I'd like to do more.)

Spot metering tells the camera to use only a small portion of the image for figuring out the proper exposure. This is useful when you have a very backlit subject and you only want to expose based on the subject, and not have the camera get confused by the bright background. I found that the non-pro canon bodies had something similar to a "spot" meter but it wasn't small enough to be useful for what I do. With the "N", I haven't tried it, but its spot meter is much smaller and would probably work.


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