Another neophyte lens question

[Stefan A]

On the slr lenses, the zoom range is expressed as Focal Length in millimeters. How do those millimeters compare to the 3x, 12x, etc. How do I figure out what "X" an slr lens is?

Stefan

[nwyman]

I don't think there really is an X factor in SLRs, because the body itself has no lens to multiply against.
The only multiplication factor I can see with SLRs is the focal length multiplier tthat gives you the equivalent of a 35mm camera, and that varies from camera to camera, doesn't it?

Nancy (getting into muddy waters)

[Ronald S. Jr.]

You can tell. take, for example, the 100-400mm f/4.5-5.6L IS USM lens. Technically, it's only a 4x zoom. This is totally irrelevant, though, as is any "?x" lens. What matters is the actual focal length, which is why the slr lenses don't say "4x". The 100-400L is a 4x zoom, but when you're starting out at 100mm, as opposed to 24 or so mm like most P&S cameras, you're already past the "zooming ability" of the smaller camera. Add to that, that the 100-400 goes all the way to the super telephoto length of 400mm, and you're at roughly 4x longer reach than the "tightest zoom" on the P&S. It's all optical zoom, too, not digital zoom, so there's no loss in quality, either.

Did I confuse you enough?

[Ronald S. Jr.]

If you don't want to read that long explanation, just take the focal length of the long end of the lens (the highest mm), and divide it by the wide end (the smaller number). So, if you have a 28-135 lens, for example, you divide 135/28, and you get approx. 4.8. That means the 28-135mm lens is a 4.8x zoom.

Again, the multiplication factor means nothing; the focal length is what tells you how far you can "zoom"

[Stefan A]

OK - so what kind of lens would I need to match the zoom of the the S2IS?

Stefan

[nwyman]

You can tell. take, for example, the 100-400mm f/4.5-5.6L IS USM lens. Technically, it's only a 4x zoom. This is totally irrelevant, though, as is any "?x" lens. What matters is the actual focal length, which is why the slr lenses don't say "4x". The 100-400L is a 4x zoom, but when you're starting out at 100mm, as opposed to 24 or so mm like most P&S cameras, you're already past the "zooming ability" of the smaller camera. Add to that, that the 100-400 goes all the way to the super telephoto length of 400mm, and you're at roughly 4x longer reach than the "tightest zoom" on the P&S. It's all optical zoom, too, not digital zoom, so there's no loss in quality, either.

Did I confuse you enough?

Oh, yeah! <g>

Nancy (reaching for aspirin)

[nwyman]

OK - so what kind of lens would I need to match the zoom of the the S2IS?

Stefan

something like a 10mm - 120mm?
or a 12mm - 240mm?



Nancy (not sure that there are any such things, but just playing with numbers)

[snowrdr]

OK - so what kind of lens would I need to match the zoom of the the S2IS?

Stefan

The 35mm film equivalant focal length range of the S2IS is 36mm to 432mm :D

The bebit page is a great place to see the specs

http://web.canon.jp/Imaging/pss2is/spec-e.html

[Stefan A]

So, now I am seeing 2 different answers. Nancy's answer sounds good because those lenses would be cheaper. But some of those lenses that go to 400mm costs thousands.

Although I don't own an slr right now, I am trying to learn everything I can now in case I want to get one.

Stefan

[nwyman]

but my answer was based purely on math - I have no idea if such lenses are available.
And having just purchased the Rebel XT - I'm trying to learn as much as I can so as not to appear totally ignorant when entering a camera store. It's an uphill battle.

Nancy

[Stefan A]

Yeah, today I went to Best Buy and handled the rebel xt and the 20d. I cannot stop thinking about the idea of getting one of those. But I am just trying to learn all I can . To be honest, the Rebel really feels like a P&S in your hand as compared to the 20d. But from everything I have read, the xt is very close in quality and features. Still, the build quality concerns me about the rebel xt.

Stefan

[MiG82]

Zoom is the ratio of tele/wide focal length. Nothing more and without exceptions.

As you might be able to tell, it says nothing about the field of view, just how much it changes.
The thing is, on P&S cameras they tend to stick to the mid range focal lenghts, so the zoom factor can roughly tell you about the FOV range. On an SLR lens it only gives an indication of the lens' versatility. Sigma 300-800 = 2.5 times zoom. Canon 28-300 = 10.7 times zoom. Primes = 1 times zoom.

[RossW]

Stefan,

You're mixing two related, but quite different measures over the course of this discussion. The "12x" zoom in your S2 merely notes the relationship of the widest angle (shortest focal length 6mm) to the narrowest (longest focal length 72mm). A 10x lens could be 10 - 100, 15 - 150, 35 - 350 etc. So Nancy's got this one OK. Used to be a 10x lens was only found on a decent video camera. Most still cameras had zoom ranges of 2x or 3x or thereabouts.

Stefan, your follow-up asks about the second measure: the relationship between lens focal length and how much magnification it can supply -- and that depends on the size of the digital sensor (or film frame). Snowrdr gives you the focal lengths that a 35mm film camera would need to make an image equivalent to your S2. The S2's sensor is smaller than a 35mm film frame, so its 6mm focal length is on par with a 35mm camera's 36mm. I don't know if there is a single lens for a 35mm camera -- or even a DSLR -- that is the equivalent of the S2's zoom. More likely, you'd need at least a couple of zooms or a handful of prime (single focal length) lenses to cover the same range. That said, I don't mean to imply the S2 is itself the equivalent of an SLR; the larger sensor size in a DSLR (or film frame in a film SLR) almost guarantees a potentially higher quality image in terms of sharpness. And that's what Ron was pointing out. Taken a step further, that's why medium and large-format cameras are used for extremely high-quality portraits, product shots, scientific work, etc.

[Stefan A]

Well, I am reading all of your thoughtful answers, and they make sense. I have learned that there is no single lens that would give me the same magnification of the S2IS. But it would have to be a combination of lenses to get the whole range.

Lets say I am standing in a particular location with an slr and the S2IS. With the S2IS I zoom all the way in - to 12x, and take the picture. Now, lets say from the same spot I want to get the same shot with the slr. I want the shot to look just as close. Which lens do I reach for?

The thing is, the 12x zoom was one of the main reasons why I bought the S2IS. If I end up buying an slr, I need to decide if I will sell the S2IS or if I will keep it to get those close shots. Yes, I realize that there are lenses that will do what I want, but the issue is money. If I can't afford the lens that will allow me to get that close, I may have to keep the S2IS until I can afford it. That is why I want to know which lens I would need.

Stefan

[RossW]

...Lets say I am standing in a particular location with an slr and the S2IS. With the S2IS I zoom all the way in - to 12x, and take the picture. Now, lets say from the same spot I want to get the same shot with the slr. I want the shot to look just as close. Which lens do I reach for?

Stefan

For a 35mm film SLR (or "full frame" DSLR), the equivalent lens would be 432mm. A DSLR with a slightly smaller sensor would need something smaller... I believe this is the "1.6" factor mentioned sometimes.

Since 35mm cameras were around for so long, I think many new converts to digital still think in terms of the 35mm equivalents for lenses when shopping or choosing a lens to use. Since different digicam manufacturers use different-sized sensors (and there are differences even in one manufacturer's product line) the 35mm equivalent becomes the common link for comparisons.

If I end up buying an slr, I need to decide if I will sell the S2IS or if I will keep it to get those close shots.

Keep the S2... you'll want one you can just "toss" into your briefcase or backpack when you don't want to take along an SLR kit. Or let someone use as your "backup" shooter at events.

[sonnyJ]

Regarding 35mm film lens with large zoom ratio. Tamron makes a 28-300mm lens which is a 10.7x zoom
If used on DSLR camera with 1.6 sensor ratio then it would be like a 44.8 to 480mm zoom on 35mm platform (still 10.7x zoom)

Stephan - you can get a teleconverter of about 1.5 power for $120-150 - That would make the S2 a 54 to 648mm 35mm equivelant - You gain in telephoto but lose in wide angle

[Stefan A]

Keep the S2... you'll want one you can just "toss" into your briefcase or backpack when you don't want to take along an SLR kit. Or let someone use as your "backup" shooter at events.

Yeah, I know I will want a backup. But the idea was to replace it with a much smaller canon. That way, I get what I want. And my wife gets to have one in her purse. But of course zoom level will not be the same. So you see where I am coming from now. Plus, I want to still have a small canon so I can keep coming to this forum and doing the contests for small cameras :).

After looking at some prices, it looks like I can get up to 300mm with the Tamrons for under $200. The 28-300 is under $400 and I guess that's not too bad.

Now, if only I could afford the body :)

Stefn

[nwyman]

Now, if only I could afford the body :)

Stefn[/quote]

in truth, it makes me wonder why we used to quibble so over the price of the memory cards! <g>

Nancy