I absolutely recognise that. But, with respect, the issue is one of understanding. we are in the middle of a changeover where digital will take the place of analogue.
the understanding of the capacity of lenses, in this case the angle of view of a "sized" lens, will change.
But right now, when I see an 18mm lens, my mind gives me almost automatically a view of what I might see thru that lens. and my Canon supplied lens doesnt.
Just a whinge from an older person who welcomes change but occasionally feeels that perhaps there's a better way.
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
The 18mm is an absolute measurement that defines the optics of the lense. A lense with same focal length will give very different results depending on the format and size of the film or sensor that it is 'projecting' the image onto. Panavision have a little web tool that lets you work it all out mathematically (if you feel so inclined):
In understand your feelings. But rather than commiserate, as we old geezers are inclined to do, lets looks at what the real possibiites are.
I understand that we are in the middle of a great transistion from primarily analogue photography to primarliy digital photography. But recongnizing that doesn't lead me to grasp any magic way to deal with the issue you mention. What the change may mean is that the importance of cameras with frame sizes of about 36 x 24 mm will decline. This seems to be a peculiar motivation for somehow solidfying the notion that field of view would be best described in terms of the focal length of a lens that would have given that field of view on a kind of camera that hardly anybody uses anymore.
What would really be better would not be to enshrine the 35-mm outlook on field of view, but rather to begin thinking of field of view in terms of angle, the real property of interest (as is often done in serious technical photography). Then for lenses that could be put on cameras with different sized sensors, we could have a card or something that would show what the field of view (as an angle) was for each focal length setting of the lens for that camera.
For lenses suitable only for cameras with one sensor size (such as the Four Thirds System lenses, or the EF-S 18-55), they could be marked (and "advertised") in terms of a range of field of view angles. If they had a zoom ring, it could be marked in FOV angle.
But lets assume that talking about field of view in terms of field of view is too simple, and thus not acceptable to the user community.
Going back to where you started, I think you are advocating "designating" the EF-S 18-55 mm lens in terms of its range of 35-mm equivalent focal lengths when it is used on the only cameras for which it is (so far) suited. Thus, perhaps it could be called a "V29-88" lens, where "V" by convention would mean that the reference was to the field of view of the lens in terms of full-frame 35-mm equivalence (in mm).
But now what would Canon do for their EF 17-40 mm lens, which will work (so far as I know), on cameras with these sensor sizes:
22.7 x 15.1 mm (CanonEOS 10D, EOS 300D)
28.7 x 14.1 mm (EOS 1D)
35.8 x 23.8 mm (EOS 1Ds)
36 x 24 mm (EOS full-frame film cameras)
Well, you could designate that a "V17-40xK" lens, meaning, "giving the field of view that would be given on a full-frame 35 mm camera by a lens of focal length 17-40 mm multiplied by the factor K, which is the ratio of the frame size of a full frame 35 mm camera to the frame size of your camera".
But of course that's essentially what we have now. It would just be a moore muddled way to label it "17-40"
I hope that you are not advocating now labeling that lens "27-64 mm" because that would be the "35-mm effective focal length" it would have on a 300D. I think the users of other format size cameras would be rather disappointed.
I would never advocate describing the kit lens as having a focal length of 29-88 mm. Not only is it not technically true, but more importantly, doing so would lead to errors in making other calculations. (Remember, field of view is only one of the properties affected by focal length.) If we somehow believed that the shortest focal length of that lens was 29 mm, we would get the wrong result if we went to calculate depth of field, or bellows factor for closeup work.
Of course, we could always learn that, "with lenses intended only for use on the 300D, we need to divide its 'advertised' focal length by 1.6 before using it in any optical calculations." We could call that result its "300D equivalent focal length".
So, those are some things that the industry could do to address your concerns. Which of those, or which something else, do you advocate? I'm not sure from your posts what you would like to see happen. (Other than us somehow moving again to a situation when most people shot with cameras having a frame size of about 36 x 24 mm!) We have to choose from among doable alternatives.
I know this is tough on you old timers. It's even complicated for us young fellows (I'm won't be 68 for another 2 months).
Best regards,
Doug
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
Over a delicious dinner here a few minutes ago, my bride, Carla, the Cherokee Sage (also known as Red-fox-who-looks-through-lens) and I have solved your problem with something I can do from right here and I will do in just a few lines.
We have invented a new adaptive unit of measure, the franklin (Fkl). One Fkl equals D/43.3 mm, where D is the diagonal size of the sensor of the camera we are using, in mm. Focal lengths in mm can be converted to Flk by dividing by the quantity D/43.3, as applicable to your camera.
For an EOS 300D, 1.00 Fkl = 0.630 mm.
For an EOS 1D, 1.00 Fkl = 0.796 mm.
For an EOS 1Ds, 1.00 Fkl = 0.992 Fkl
Now here is where I actually solve your problem:
I, Douglas A. Kerr, P.E., do hereby declare that the focal length range of the lens also described as the Canon EF-S 18-55 mm f/3.5-5.6, when used on a Canon 300D camera, is 28.6-87.3 Fkl.
Now the amazing thing about this is that, if you remember what focal length a 35 mm lens, say, would give on a full-frame 35 mm still camera, you will get that same focal length by setting your "kit lens" to a focal length of 35 Fkl.
Naturally, to do this conveniently in the field you will need to put a paper label calibrated in franklins (Fkl) over the current focal length scale on the lens (the one that presently is marked in those silly millimeters). Once you've done that, you will be all set.
Those with Canon EOS 1Ds cameras will be pleased to know that they can just mark the existing focal length scale on their lenses to be in Fkl, and they will be within about 3/4% of being correct.
We are pleased to have solved, by this simple stroke, this problem which has of late been so vexing to (some) present-day photographers.
Best regards,
Doug
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
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I personally see no reason to maintain a 4x6 format of 35mm film, other than the simple expediency of using existing 35mm format lenses.
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The question of an "ideal" aspect ratio for cameras is widely debated, and no single conclusion is reached.
The "Four Thirds System" is a new norm for digital cameras in supported by several prominent manufacturers (not. at present, including Canon). One of its premises is a 4:3 aspect ratio for the sensor. (That's not where the system's name comes from, supposedly, but rather that the sensor size is one that would described, in that silly system based on the "bottle size" of Vidicon tubes, as "4.3 inch".) (In that system, a sensor size of 8.6 x 6.6 mm came to be described as the "2/3 inch" size, since that was the diameter of the bottle of the Vidicom having that sensor size - not a digital sensor, by the way.)
Many camps of "medium format" film photographers "swear by" aspect ratios that are "closer to square" than the 3:2 of full frame 35 mm, such as 1:1 (6 x 6 cm, indeed "square"); 6:7 (6 x 7 cm); and 4:3 (6 x 4.5 cm); and of course the 4:3 ratio is used in the "half-frame" 35 mm format (36 x 24 mm), traditional 35 mm motion picture work (very nearly 36 x 24 mm) traditional video cameras, and many modern digital cameras. Going in he other direction, a 16:9 aspect ratio is the norm for "HDTV" video, and is very nearly the ratio for one of the standard delivery "crops" in the Advanced Photo System (APS), its "H" crop.
Getting back to your original observation, there is in fact nothing that I know of about the EF- series of lenses which suggests their use only in a 3:2 format ratio situation. They would from an optical standpoint be, as near as I can tell, well suited for a 4:3 frame sizes (for example) of up to perhaps 34.6 x 25.6 mm.
Then there are those who swear that the ideal aspect ratio for a camera is that dictated by the "golden mean", or "golden section", flowing from classical Greek philosphical and architectural principles, of about 1:1.618 (roughly 8:5, if we like to think in terms of a ratio of small integers).
Im practice, as you recognize, it doesn't seem to matter much. We take images with whatever aspect ratio our camera's manufacturer has adopted, and crop the result to suit our artistic wishes and the format which, for either artistic or pragmatic purposes, we wish for our output. It is intersting that, in an earlier era, I would flip the camera to wishever orientation seemed to best match what I expected would be the orientation of the output I foresaw for the shot. Now I almost always shoot with the camera "rightside up" - it makes it easier to read the indications in the viewfinder finder!
And we should prbobably keep in mind that the original Kodak camera, a "one-use" camera as we would say today, had a round frame, certainly best exploiting the "image circle" of its lens.
Best regards,
Doug
White Balance so easy, even our 5 year old can do it.- Melissa Strickland
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