Question about Camera?

[mjhulik]

As I posted before I'm in the market for a DSLR camera and I had some other questions?

1. How do I know how much zoom a lens has, for example if its a 80-300mm lens how much zoom is that? I don't really know how that works.

2. If I take a photo say at max 10.1 mp which is about 3888 x 2880 or something like that and I bring that photo into photoshop and I magnify that photo and it starts sawtoothing, how is that fixable or do I need a different lens?

if anyone doesn't understand what I'm trying to say just let me know I really didn't explain that to well.

3. Can anyone explain the difference in ISO's?

I think thats about it for now, thanks for those who answer!

mjhulik

[RichNY]

"1. How do I know how much zoom a lens has, for example if its a 80-300mm lens how much zoom is that? I don't really know how that works."

Zoom is a meaningless statistic that states how many times the longest focal length is compared to the shortest length. So a 20-100mm would be 5x zoom while a 200-400mm is only a 2x zoom.


"3. Can anyone explain the difference in ISO's?"

Taking a properly exposed picture is like getting a decent tan. Both require a certain amount of light for a certain period of time. If you are in direct sunlight you won't need to stay out long to get a tan; if there isn't as much sunlight you'll need to stay out longer to get the same results.

With photography, setting your apperature controls how much light exposes film or reaches the sensor. The shutter speed controls how long the sensor is exposed.

The third component of this is ISO or skin fairness using my analogy. A fair skinned Irishman might not need to stay out in the sun for as long a time as a darker skinned individual because he has increased sensitivity to the sun.

With film or digital, setting your ISO changes the sensitivity to light. With normal light most people shoot pictures at ISO 100. If you up your ISO to 200 that makes your camera 2x as sensitive to light allowing you to take a picture with 2x the shutter speed for a given aperature setting.

Where this becomes important is in low light situations when you have already set your aperature as large as it can get to allow the most light in, and your shutter speed is too long to be able to take a picture. The solution is to increase your ISO to a higher value so that you can have a faster shutter speed.

[mjhulik]

Thanks for the clarification.

[John_Reed]

As I posted before I'm in the market for a DSLR camera and I had some other questions?

1. How do I know how much zoom a lens has, for example if its a 80-300mm lens how much zoom is that? I don't really know how that works.
If you're looking for equivalent magnification, like the "power" of a pair of binoculars, focal lengths are usually normalized to ~50mm, the focal length of a "standard" lens from old 35mm days. If you have a zoom lens with range 80-300mm with no multiplier, that would be a "power" of 1.6X to 6X the zoom of a "normal" lens. If your zoom lens is mounted on a dSLR with a crop factor of, say, 1.5, then the "power" of the lens would range from 2.4X to 9X. OK?


2. If I take a photo say at max 10.1 mp which is about 3888 x 2880 or something like that and I bring that photo into photoshop and I magnify that photo and it starts sawtoothing, how is that fixable or do I need a different lens?

Every digital photo is made up of a grid of pixels. If you stand far enough back, you won't be able to see the individual pixels, but if you blow up an image big enough in pixels to see "sawtoothing," then you're too close! An image the size you described should easily be printable on a 19" by 14" sheet of paper with no "sawtoothing" visible to the human eye. So there's nothing you need to fix there.

[Pave]

Just one more thing concerning the zoom that has not been mentioned here (I think). Usually the number (ex. 12x) has little "35mm eqiv." behind it. It means that the zooming range is (in this case) 35mm - 420mm (12x35mm = 420). The 35mm is usually considered the starting point for zooms. Except for wide lenses or teleconversion lenses or fisheyes or somesuch things. Generally speaking this applies to almost all cameras with nonchangeable lenses.