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Old Mar 27, 2006, 4:04 AM   #1
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I have a Kodak P850with 12x optical zoom and specs stating:

optical focal length (35mm equivalant;36 - 432mm)

question:

For a DSLR what size lens would give me comparable focal length?
It is confusingon the differences between 35mm rated length and Digital,
they appear to be different.

For example, how close would a Nikon D50 with 70-300 be in term of total zoom?

is it really 300mm vs. 432mm?
or is the 432 simply the rating for 35mm.

thanks in advance for any help
and I apologize if this has been covered, I cant seem to find info on it
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Old Mar 27, 2006, 4:39 AM   #2
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This has been the subject of much discussion and a lot of argument which I won't go into here and hope I won't stir up again.

The equivalent focal length gives you a measure of the equivalent field of view that the lens gives where compared to a 'standard' 35mm camera.

There are many different sensor sizes in digital cameras and each sensor size needs a different focal length lens for a given field of view.

Even between DSLRs there are differences Canon for example make full frame sensors which have a sensor the same size as 35mm film so the field of view remains the same. On Canon's smaller sensors the equivalance is 1.6 whereas for Nikon such as the D50 it's 1.5.

So your 70-300 on a D50 is still a 70-300 but it gives the field of view that a 105-450 lens would give on a 35mm camera simply because the smaller sensor is onlyusing a part of the available image.

The Kodak P850 uses a much smaller sensor and the actual focal length of the lens is 6.0-72.0mm.


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Old Mar 27, 2006, 1:35 PM   #3
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thanks for your reply.

let me try to ask a different way.

I get 12X optical zoom on my p850.
I can zoom into a subject(i.e. a bird) and get a nice tight closeup shot.

Would the 70-300mm on the d50 give me the same comparable zoom?

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Old Mar 27, 2006, 2:28 PM   #4
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The "12x" zoom on that camera is really a marking term and nothing more. Here is why:
It only describes the ratio of the long end of the zoom to the short end of the zoom. So both these lenses are "10x" zooms:
10-100 f/4
50-500 f/4

Both of those would be sold as "10x" zooms but clearly they are very different lenses. The first is very wide angle and good for buildings, landscapes and more. The second is a telephoto lens (very long) and good for birds, animals, sports. But it has no wide angle at all (50mm is basically human visison.)

But to your direct question. The 70-300 would give you basically the same image on the D50, with the other advantages of it being a DSLR.

But the big question is max aperture. What was the aperture on the P850? A quick look shows it to be f/2.8-3.7. that is a very good aperture, as it lets you get a high shutter speed.

Getting a lens on a DSLR with that aperture will cost lots of money. Is the lens you're thinking about the:
Nikkor AF 70-300mm f/4-5.6 ED
?
If so, then its an "average" quality lens for sharpness. The auto-focus speed is very slow (so you'll miss many bird shots as the bird leaves before AF is achieved.) I've never used that lens (I'm a Canon shooter) but it doesn't look great.

But the real problem is the aperture. At around 400mm it will be f5.6, while your other camera was f3.7. You'll loose over 1/2 your shutter speed because of that, making stopping the action hard. So on the Kodak you might shoot at f3.7 1/1000, but on the D50 you would be at f5.6 1/500 (less, actually, but I don't know how much less.) You're only choice would be to bump the ISO one mark higher on the D50 than the P850 to make up the shutter speed loss.

Eric
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Old Mar 27, 2006, 2:34 PM   #5
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techgeek419 wrote:
Quote:
thanks for your reply.

let me try to ask a different way.

I get 12X optical zoom on my p850.
I can zoom into a subject (i.e. a bird) and get a nice tight closeup shot.

Would the 70-300mm on the d50 give me the same comparable zoom?
At the high end, it will give you a slightly tighter shot then your Kodak - i.e. 450mm. For other reasons, it should also give you a shot with better detail.


Dave
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Old Mar 27, 2006, 3:35 PM   #6
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Eric, while technically you're of course entirely correct, I disagree with you on two things--of course, AF speed is rather slow on that lens. However, coming from a Kodak P850, AF is likely faster, and more importantly, much more accurate with a D50.

Second, yes, the maximum aperture is a bit slower on the 70-300 (even more so when you consider that stopping down is advisable). However, I suspect that ISO 800 on the D50 will likely be superior to the P850 at ISO 100, so moving to a D50 (or any DSLR) will likely result in a gain in shutter speed. The D50, even with this pedestrian lens, will make stopping the action much more feasible than a P850.
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Old Mar 27, 2006, 3:41 PM   #7
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Eric is right about the slower aperture but mised the fact that the D50 has a minimum ISO of 200 where the P850 minimum ISO is 50.

You could shoot with the P850 at ISO 200 but the resulting image is unlikely to be as good as the D50 at 200 and you could shoot the D50 at ISO 400 without losing much in the way of quality. So acheiving comparable shutter speeds with the slower lens isn't likely to be a problem.
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Old Mar 27, 2006, 6:33 PM   #8
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Ah, I did not realize that the minimum ISO was 50 on the Kodak.
techgeek419, do you know what ISO you normally shoot at? That will change my calculations greatly.

Eric
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