Photoboy Loc: Maryland Eastern Shore

What is a rule of thumb for converting a telephoto in millimeters (e.g. 300mm) to power (e.g. 3x or 5x)?

Joansgirl64 Loc: Maine

I don't know the answer, but I have been curious about that too. My P & S has a 26 x zoom. What DSLR lens would be equivalent in zoom ability?

JimH Loc: Western South Jersey, USA

There was a thread about this about two month ago. My feeling is there is no 'direct' relationship. You want to treat a lens like a pair of binoculars and I don't think that's exactly accurate. I've never seen lenses advertised as "10x" power or "3x magnification" like binoculars are.

The only ratio that makes any sense in a zoom lens is the ratio of narrow to wide field of view, eg. a "18-135" zoom lens has a 7.5x zoom range, but you don't see an 18-135 lens noted as such except in passing.

I wouldn't be concerned about it.

Photoboy Loc: Maryland Eastern Shore

It's not a concern, just curious. When one buys a point and shoot, the lens is described a 3x, 5x, etc. An SLR or DSLR lens is in mm, but also provides magnification, if it's a telephoto. There must be some way to compare.

Nikonian72 Loc: Chico CA

Magnification depends on the size of the camera's CCD or film size. As an example, the normal lens for 135 format (35-mm film) cameras is 50-mm. 300-mm lens/50-mm lens = 6x normal. For the Nikon DX format, the "normal" lens equivalent is about 37-mm, so 300/37 = 8x normal.

SQUIRL033 Loc: Chehalis, WA

there is no DSLR zoom lens that offers 26x that i know of. what's the shortest focal length your P&S offers?

Photoboy Loc: Maryland Eastern Shore

That makes sense. Thanks.

Paw Paw Bill Loc: d

When a P&S indicates a lens with some particular "X" power, it is not referring to the telephoto magnification. It is the ratio of the widest setting of the lens to the narrowest setting. For example, if the wide setting is 10mm and the telephoto is 160mm then the lens is a 16x. If you have a lens that starts at 20mm and goes to 200mm then it is a better lens for telephoto than the 16x yet it would be called a 10x because 200 divided by 20 is 10.

For full sized sensors, 50mm to 55mm is considered normal. For DX, 35mm is approximately normal. So if you want telephoto magnification similar to binocular power readings, you divide the maximum mm that your lens has by the normal factor for your camera. Example, a DX sensor with a 350mm lens should be approximately 10 power since 35mm is near normal.

Again, don't get fooled by big numbers on point and shoot lenses. It is usually because they start at a lower mm setting on the bottom. It does not mean that they are a better telephoto lens. This really is good in a way, since many photos are inside with a group in a small room, so a wider lens is a benefit.

Gidgette Loc: Boerne,Texas

Just bought a Olympus P&S that had 36X. They said it was the same as 864mm.

KrazyKyngeKorny

Focal length/50.

50=1x, 100=2x, 300=6x

Gidgette Loc: Boerne,Texas

Divide 864 by 36X =24mm per X. Wonder is this applies to all conversions.

KrazyKyngeKorny

The zoom number on a digital is the ratio from the short focus to the long focus. 38 to 102 is called 3x (102/38 is actually 2.684+). BUT, 38 is .69x, while, 102 is 1.86. If a lens is 24 to 102, it is called 4x zoom. Telephoto power and zoom are two different things. It's done to confuse you.

The 50 (actually, 55) figure was standard with 35mm film. Many companies, now are using 38mm as the 1x. That makes their lenses appear better than they actually are. For reliability, use the focal length as your standard.

CAM1017 Loc: Chiloquin, Oregon

As mentioned by several people, in a full frame 35mm film camera and a full size sensor Digital camera a 50mm lens is considered to be 1x. A 200mm lens would = 4x, 400mm lens = 8x. This does dont hold true with "C" size sensors that are used in mid size Digital camera's like the Canon T1i. These camera have a magnification factor of 1.6 because of a smaller sensor size. I think that this 1.6 factor does not apply to all camera brands. Some may have a slightly smaller number. What this means is that you multiply the lens focal length by 1.6. Your 100mm lens nows is equal to a 160mm lens. If you divide this by 50 you have a 3.2x lens. Your 400mm lens becomes 640mm and gives you a 12.8x lens. On the other end, your 24mm lend is a 38mm and not as wide angle as you might like.

MtnMan Loc: ID

Hi,

Yes, you can generalize the conversion from a 35 mm film to a DX sensor camera (most non-professional DSLRS) by the Crop factor. It is 1.5 for Nikons. It might be 1.6 for Sony. As noted below it comes from the sensor size.

So the 300 mm telephoto on my DSLR is like a 450 mm on a 35 mm camera. Using 50 mm as the standard view for the film camera I'd say that means about 9X...close enough to the 8 below.

It works the other way also. So 18 mm wide angle on my other lens is like a 24mm on a film camera.

Regards,
Larry Leach

[quote=Nikonian72]

pdwoodswood Loc: Lewisville, NC

A P&S is a digital zoom vs a DSLR lens which is optical.
A very good optical lens at 800mm is likely $25,000.00
I suppose one is made, I will have to look out of curiosity.
A question for a P&S camera; Is the digital zoom expanding fixed pixel density with greater magnification, i.e. zoom, therefore losing clarity & contrast? It would seem so, but I do not know for fact.