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Old Jul 19, 2002, 2:59 PM   #1
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Default Difference between SLR and others

The SLR doesn't seem to show how much zoom it has (3x or 10x). Does it has a motorized zoom? What other differences between SLR and a non-SLR?

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-aclive
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Old Jul 19, 2002, 4:02 PM   #2
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the term slr (single lens reflex) is a term loosely used in the digicam world.

the true slr's are the d100 d1/h/x from nikon. eos1d d30 d60 from canon. these use a conventional mirror box assy just as a standard f5 eos si from all manufacturers. the difference is where the film used to go behind the shutter is now a ccd sensor without the shutter assy. as far as the zoom goes that will be determined with the particular lens you attach. all except 1 of these also have a conversion factor. because the ccd is smaller than a frame of 35mm film you must multiply the lens you get by this factor to get it's new equivelent focal. with the current nikons its 1.5 with the d60 i believe its 1.3 the other canons i'm not sure. so it you buy a 20-35mm for your old slr and then use it on a digital slr it will be a 30-52 using the factor 1.5. now the 1 different one is from contax. the body is roughly $7000 and the lenses are Zeiss/Contax lenses. premium stuff.

now with some newer styled digicams such as the D7i from minolta and 5700 nikon they have an eyepiece in addition to the monitor on the back. that eyepiece has in it another tiny monitor (evf) to simulate the look and feel of an slr. this is a wysiwyg, what you see is what you get view of the thruough the lens experience. the d7i is a manual zoom and the 5700 is a push button zoom. as you zoom either of thes you will see the results in the eyepiece. both these models have 7x and 8x respective zooms

have i confused you?




[Edited on 7-19-2002 by sjms]
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Old Jul 19, 2002, 6:39 PM   #3
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I've never seen the term SLR used loosely in the digicam world. As a D7 owner and a long time film SLR user I'll say the D7 does not simulate an SLR. It allows precise framing when ambient light is too bright to see the external LCD but doesn't allow the precise focus control or depth of field preview of an SLR. I use my D7 more than my other cameras but have no illusions that it's a substitute for a DSLR.

Also DLSRs as well as many other digicams do use a mechanical shutter.

You forgot to mention the Olympus E-10 and E-20. Though they don't use moving mirrors but a semi-silvered fixed mirror, they are true SLRs. They also lack interchangable lenses unlike DLSR's from Canon, Nikon, Kodak and Fuji which are all based on 35mm film bodies.

[Edited on 7-19-2002 by padeye]
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Old Jul 19, 2002, 7:15 PM   #4
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It occured that neither of us explained what an SLR is. Single Lens Reflex. That means you view through the same lens the film or CCD is exposed through. This elimnates parallax errors in framing from using a secondary viewfinder lens. The reflex bit means a mirror which bounced the image up a ground glass focusing screen. You view this image through a pentaprism which turns the image upright.

Cameras like the D7 and CP5700 use a single lens but the EVF is showing you an electronic reproduction of the CCD image as opposed to actually looking through an optical path from the lens.
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Old Jul 20, 2002, 12:45 AM   #5
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Thank you, sjms and padeye:

The purpuse of SLR is to get the eyes same view as the film or CCD, which is what an EVF can do. So my question is: what is the functional difference between a digicam with EVF and capability to mount add-on lens (I think the camera maker can also build better manual controls into it just like what an professional SLR can do) and a SLR professional? Can the lenses on a digital camera be changed? Can those interchangeable lenses have a motorized zoom?
Another question: what is the difference between a mechanic shutter and an electronic shutter (speed?)

Thank you!
-aclive
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Old Jul 21, 2002, 5:11 PM   #6
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ok. we both covered the ground well. but the D7/i is not an slr due to the lack of the physical reflex viewing mechanism (ie: prism and mirror. it gives a direct view to the ccd with electronic pick off of the image to view in the evf. this of course is the true view. it just works pretty cool. i prefer it to the the reviws screen which is off 90% of the time
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Old Jul 21, 2002, 5:31 PM   #7
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a mechanical shutter is one that is independent of any electrical power. an olympus om-1, pentax k1000, nikon fm series and a slew of others in the '70s and '80s. when you advanced the film using the lever that also reset the shutter release for the next shot. an elegent and sophisticated gear/lever/spring system set the shutter speed timing. i still love my om-1 and om-3 because even if the the battery failed i pulled out my trusty old gossen or minolta hand held meter. and continue fireing away. of course mechanical shutters are subject to timing errors due to many factors such as temp humidity and age. but most were pretty darn accurate. they were the swiss watches of the camera world.
electronic shutters today are electromagnetically controlled quartz timebased wonders of technology. super accurate i believe now out to 1/16000 of a second. computer controlled. in the early days of electronic shutters most manufacturers had at least one manual speed. todays models without batteries they're great paperweights.

my f5 manual claims its shutter speed/accuracy from the decay of some rare element nobium or something like it. all i know is its fast accurate and can eat a roll of film in a heartbeat. also gives me some good pictures too most of the time.

[Edited on 7-21-2002 by sjms]
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Old Jul 21, 2002, 6:32 PM   #8
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I don't think that's what aclive is referring too. Most modern cameras used electronic based electro-mechanical shutter; whereas most digicam DO NOT have any shutter of anykind @ all, but an electrical signal commands the CCD to perform an equivalent 'sample' on its internal sensors (much like a Sample/Hold in an A/D circuit). On the D60 and some others, there's a slower mechanical shutter strictly there to protect the CCD and will open @ slower speed.

This chip features an electronic shutter...

[Edited on 7-21-2002 by NHL]
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Old Jul 21, 2002, 11:42 PM   #9
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ok the dancing fingers get confused sometimes
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Old Jul 22, 2002, 8:12 PM   #10
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Thank you, NHL, about the shutter question

I still want to clarify: when we talk about a shutter speed of 15 seconds, is the CCD chip really exposed to light for 15 seconds?

-aclive
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