The New Standard Lens?

[Icebreaker]

I may be over thinking this (or maybe nitpicking,) but is a 50mm lens really standard for the 10D/300D?

My reasoning: 50mm closely matches the diagonal on a 35mm frame, using Pythagoras 43.26mm. So applying this to the CMOS sensor the diagonal comes out to be 27.26mm, rounding up to 30mm. Now let me really stick out my newbie neck a reason then, that a 18mm lens (30/1.6) would be the “standard lens” for these digital cameras.

Am I wrong in my thinking?
Your thoughts and observations Please
Icebreaker

[CyberDyneSystems]

35mm is the closest to a "standard" which gives you a 56mm "effective" focal length.

On a 35mm film negative it was 52mm that was really "standard"... no idea why they fazed them out.

[PacAce]

I may be over thinking this (or maybe nitpicking,) but is a 50mm lens really standard for the 10D/300D?

My reasoning: 50mm closely matches the diagonal on a 35mm frame, using Pythagoras 43.26mm. So applying this to the CMOS sensor the diagonal comes out to be 27.26mm, rounding up to 30mm. Now let me really stick out my newbie neck a reason then, that a 18mm lens (30/1.6) would be the “standard lens” for these digital cameras.

Am I wrong in my thinking?
Your thoughts and observations Please
Icebreaker

I followed you up until the 27.26mm (rounded to 30mm). Then you lost me? Why is you then divide this number by 1.6 to arrive at 18mm??? You should have just stopped at the 30 to arrive at the "standard lens" for the 10D.

[ilya]

Maybe some of the more experienced people could comment on the concept of "standard". I haven't heard that term applied to a 50 mm or any other lens as standard to a body type. Is there some traditional understanding of a "standard" lens? If there was, wouldn't the math lead to a 30mm rather then 18mm?

[Conor]

50mm is a standard lens on a film camera

to get the same 50mm on a 10d

28mm X 1.6 = 44.8mm is as close as you can get since they dont make a 30mm prime that im aware of.

[fwhitesides]

Maybe some of the more experienced people could comment on the concept of "standard". I haven't heard that term applied to a 50 mm or any other lens as standard to a body type. Is there some traditional understanding of a "standard" lens? If there was, wouldn't the math lead to a 30mm rather then 18mm?

I think that on 35mm film, a 50mm lens gives the approximate view that you would normally see with your own eyes. Or at least that's what the theory is.

[PaulB]

Many would argue that the most natural, the ideal, view that you get on FF 35mm is with a 'standard' focal length of between 40 and 45mm - do the maths. The 50mm was adopted by Leitz as a 'standard' lens because a 50mm is easier to make than a shorter focal length, but is close to the ideal.
In reality a much wider angle of view is needed to represent what we see - but even this is a fudge because or vision is only sharp on the objest our eyes are fixed on at any moment, and this changes many times a second as we 'scan' an object or scene.

[Icebreaker]

The way I saw it if I put a 100mm lens on and the 10D/300D "sees" 160mm, then for the camera to see 30mm then one must put on a 18mm designated lens 30/1.6. Am I wrong :?: [/b]

[Orogeny]

Is the term more properly "normal" rather than "standard"?

Tim

[PacAce]

The way I saw it if I put a 100mm lens on and the 10D/300D "sees" 160mm, then for the camera to see 30mm then one must put on a 18mm designated lens 30/1.6. Am I wrong :?: [/b]

Yes you are because when you calculated the 10D's sensor hypothenuse using the sensor dimensions the 1.6 was already accounted for.

But in any case, the 1.6 crop factor is irrelevant to the discussion since we're talking actual dimension.

[kraterz]

The 50mm lens was considered a "normal" lens because it was the easiest to make, and has been made for over half a century. Lens makers have had much experience with this focal length and it's very hard to screw up. A 50mm lens such as the 50/1.8 can be made with very few elements and is able to achieve excellent image quality.

[Terry G]

The simplest explanation/definition I ever heard for the `normal` lens was that it was the focal length which equalled (or was at least the nearest match to) the diagonal of the formats `frame` - 50mm for 35mm format, 80mm for 6x4.5, 90mm for 6x7, 150mm for 4x5 etc. etc.

These were/are the focal lengths commonly called `normal` lenses and often came bundled with a particular camera (before zooms became more commonly accepted).

They all give the same `look` to a shot despite the differing format sizes.

Note that we are `cropping` a rectangle (or square in some formats) from the circular image any lens produces, so the diagonal of the rectangle (or square) is equal to the diameter of the image circle.

regards T.