On 35mm cameras, we consider a 50mm lens as normal (it depicts the scene similarly to how our unaided eye sees the world, minus the peripheral vision). In a medium-format 6x6 camera, a normal lens is approximately 80mm because of the larger film size. And for 4x5 format, it's an even longer focal length.

The growing popularity of camcorder are invading into the traditional photographic market, together with the new emerging medium of digital photography, raise some confusion among some photographers. You might see some advertisement stamping some claim on 8X, 10X or even 15X zoom range with their camcoders. Some even allow your normal 35mm lenses to be mounted on their hardware, like the Canon's L1. For camcorder, the claims of 10X or 15X zooms, along with the new digital zooms. How do these zoom lenses correspond to 35mm photography ?

10X in 35mm photography, straight interpretation means, a zoom like 35mm to 350mm, 15X means 35mm - 525mm! The 10X or 15X claims on camcorder are somewhat meaningless unless you know the starting focal-length of the zoom and the CCD chip size.

It doesn't work that way as on 35mm hardware.

"Normal" on a camcorder varies with the CCD chip size For a l/4-inch CCD 5.2mm is normal, for a l/3-inch CCD 6.9mm is normal; and it's 9.3mm for a l/2-inch CCD.

Unfortunately, most camcorders don't advertise the focal lengths of their lenses. (Would you buy a 4X zoom lens for your SLR without knowing the focal-length range?)

The only way to determine the focal length of the zoom is to refer to the technical leaflet, the box or the instruction manual (usually the last page) or simply ask the shop assistant (I doubt many would know that).

We created a table below for your easy references:

35mm Camera

1/4" Chip
(9.6 x35mm)

1/3" Chip
(7.2x35mm)

1/2" Chip
(5.4 x 35mm)

21mm

-

-

3.9mm

24mm

-

3.3mm

4.4mm

28mm

2.9mm

3.9mm

4.3mm

35mm

3.6mm

4.9mm

6.5mm

50mm

5.2mm

6.9mm

9.3mm

85mm

8.9mm

12mm

16mm

100mm

10mm

14mm

19mm

135mm

14mm

19mm

25mm

180mm

19mm

25mm

33mm

200mm

21mm

28mm

37mm

300mm

31mm

42mm

56mm

400mm

42mm

56mm

74mm

500mm

52mm

59mm

93mm

600mm

63mm

83mm

111mm

800mm

83mm

111mm

148mm

1000mm

104mm

139mm

185mm

2000mm

208mm

278mm

370mm

As for digital zooms, these are electronic extensions of the optical zoom. The image is digitally enlarged to provide a certain percentage of extra "enlargement,'' turning an 8X optical zoom into a 64X digital zoom, for example. Just like section enlargement in 35mm, Quality suffers however. Think of it as similar to blowing up a 4x6" color print into an 8X-larger one (32x48"), then cropping out the center 4x6 inches to create the new image. Yes, it's bigger and more magnified (it appears eight times closer), but the quality and apparent resolution are greatly reduced because you are enlarging the image after it has been captured on the chip and not before - hence the detail and resolution are reduced. In color-print terms, you'd be "seeing the grain" - very grainy prints or just like ASA 3200 or 6400 prints as compared to ASA 100!

Well, sometimes if dreamy effects is desired, add a soft filter on printing, may not be a bad idea to achieve that effect.

As for photojournalists, important is the event, sometimes image quality can be of compromise.

Other useful related topics on formats (Corresponding to focal lengths of 35mm SLR lenses). Related articles on Apertures, Shutter Speeds & Depth of Field.


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