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Anonymous
March 6, 2005 11:39:19 PM

Archived from groups: rec.photo.digital (More info?)

hi,

Specification for Canon G5 says that lens 7.2 - 28.8 (35 mm equivalent 35 -
140)
The ratio at both cases 1:4
but why 7.2 equivalent 35 (not 30 or 40) ?
does 7.2 for any model equivalent 35?
if not how to know what number equivalent 35 mm?

and what does mean 1:2.0 - 3.0?
all of these numbers on the lens

Thanks.

More about : lens

March 7, 2005 6:26:46 AM

Archived from groups: rec.photo.digital (More info?)

Hi there.

The sensor, which records the picture, in the camera is much smaller than
the film in a 35mm Film Camera.

The "Crop" Factor being used for this camera is 4.86. These figures
indicate that a 35mm negative is about 4.86 times larger than the Sensor in
this camera.

This means with a lens of Focal Length 7.2mm you will get an image,
equivalent to the image you would get if you were using a 35mm (focal
length) lens on a 35mm Film Camera. That is a slightly "Wide Angle" view.

At the other end of the Zoom range - 28.8mm focal length will give an image
equivalent to a 140mm (focal length) lens on a 35mm Film Camera. Which is a
moderate Telephoto.

There are different "Crop Factors" for different Cameras. For example on
the Nikon D70 it is only 1.5. On the Canon 300D it is 1.6

The other numbers on the lens 1:2.0 - 3.0 describe the Maximum Aperture
size. At the shortest Zoom position the lens has a maximum aperture of f
2 and at the longest zoom position the maximum aperture drops to f3. The
Aperture is the size of the opening which lets light into the camera. It can
be made smaller by setting to a higher number, and the cameras auto exposure
system will do that as the lighting conditions change.

On Manual Cameras the Aperture Scale usually runs - f1.4, f2, f2.8, f4,
f5.6, f8, f11, f16, f22. each of those steps will allow half as much
light in as the previous step. The bigger the number the less light.

Hope this helps, it will all seem very difficult and technical at first.
Just keep asking questions, and you will soon learn. But do have fun taking
photos.

Roy G





"Jul" <julia.sats@sympatico.ca> wrote in message
news:fhOWd.2549$fW4.151673@news20.bellglobal.com...
> hi,
>
> Specification for Canon G5 says that lens 7.2 - 28.8 (35 mm equivalent
> 35 - 140)
> The ratio at both cases 1:4
> but why 7.2 equivalent 35 (not 30 or 40) ?
> does 7.2 for any model equivalent 35?
> if not how to know what number equivalent 35 mm?
>
> and what does mean 1:2.0 - 3.0?
> all of these numbers on the lens
>
> Thanks.
>
Anonymous
March 7, 2005 12:19:45 PM

Archived from groups: rec.photo.digital (More info?)

Jul wrote:

> hi,
>
> Specification for Canon G5 says that lens 7.2 - 28.8 (35 mm equivalent 35 -
> 140)
> The ratio at both cases 1:4
> but why 7.2 equivalent 35 (not 30 or 40) ?
> does 7.2 for any model equivalent 35?
> if not how to know what number equivalent 35 mm?
>
> and what does mean 1:2.0 - 3.0?
> all of these numbers on the lens
>
> Thanks.
>
>
The 35 mm equivalent is used to refer to a film camera using 35mm film.
Many digital camera users are ones who had used 35mm in past. These
folks had acquired a feel for the field of view, or perspective, of a
given focal length on their 35mm camera. I myself am in that category.
If the ad says the digicam has an 8mm - 24mm range of actual focal
length, I must find the chip size and do some math to see what actual
field of view the lens covers. If they say it is a 30-90 mm 35mm
equivalent, I know it goes from moderate wide angle to moderate telephoto.
Related resources
Anonymous
March 7, 2005 1:31:03 PM

Archived from groups: rec.photo.digital (More info?)

In article <3939omF5u9m82U1@individual.net>,
Don Stauffer in Minneapolis <stauffer@usfamily.net> wrote:

> These
> folks had acquired a feel for the field of view, or perspective, of a
> given focal length on their 35mm camera.

Perspective changes with the angle of the camera to the subject. Not
with the focal length.

--
To reply no_ HPMarketing Corp.
Anonymous
March 7, 2005 4:40:40 PM

Archived from groups: rec.photo.digital (More info?)

Canon G5 .. .as you typed :

7.2 -> 28.8 mm [ this is the 1:4 ratio .... == 4x zoom ] on 35mm range ..
it covers 35-140mm range.

f/ 2.0 -> 3.0 the max aperture at wide end is 2.0 and at the tele end is
3.0.

=bob=

"Jul" <julia.sats@sympatico.ca> wrote in message
news:fhOWd.2549$fW4.151673@news20.bellglobal.com...
> hi,
>
> Specification for Canon G5 says that lens 7.2 - 28.8 (35 mm equivalent
> 35 - 140)
> The ratio at both cases 1:4
> but why 7.2 equivalent 35 (not 30 or 40) ?
> does 7.2 for any model equivalent 35?
> if not how to know what number equivalent 35 mm?
>
> and what does mean 1:2.0 - 3.0?
> all of these numbers on the lens
>
> Thanks.
>
!