So, erm, which focal length is right, Mr Hedgcoe?

[Kevin_T]

This might sound like a daft question, but I'm looking into buying a "standard" lens for my D60. This has an APS- C sensor, right?

So, if I've got this right, I need a 35mm lens to give an equivalent angle of view to a 50mm lens on a 35mm film SLR- something akin to the human eye.

Then I read in John Hedgcoe's "new manual of photography" that most lenses designed for digital SLRs quote focal lengths already converted to 35mm- equivalents.
So the question is- am I looking for a lens that says "50mm" on it, or "35mm"????

Any help greatly appreciated. I feel I'm going mad here...

Kev

[Nod]

AFAIK, lenses for DSLRs have their real focal length marked on them - a 50mm lens is a 50mm lens. An APS-C sensor (as fitted to the D60) just crops the image to give an angle of view the same as a lens 1.5x longer (Nikon's Dx sensor has a crop factor of 1.5). To get a lens with the angle of view similar to that of a 50mm on a 35mm SLR, you'll want a 35mm lens.
A slight complication is that the D60 needs lenses with an Auto Focus motor built in - Nikon call their lenses with that feature AF-S lenses and Sigma call it HSM. A quick look at Warehouse Express's ad in AP shows that Nikon do a 35mm f/1.8 AF-S lens and Sigma have a 30mm f/1.4 HSM.

[MickLL]

I'm not an expert. Mind if I repeat that - I'm not an expert.

I know of NO camera that displays "equivalent focal length'. All the cameras and lenses that I know display only the actual focal length. (Ignoring manufacturing errors that some pedant will point out )

MickLL

[swanseadave]

Are you there,Erm? This one seems to be for you.

[LargeFormat]

I know of NO camera that displays "equivalent focal length'. All the cameras and lenses that I know display only the actual focal length.

Konica Minolta A2 in front of me has a zoom of 7.2 - 50.8 actual and also says 28 - 200 (Equiv. 135).

[swanseadave]

I know of NO camera that displays "equivalent focal length'. All the cameras and lenses that I know display only the actual focal length.

Konica Minolta A2 in front of me has a zoom of 7.2 - 50.8 actual and also says 28 - 200 (Equiv. 135).

I think that all digi compacts have the focal length range on the camera somewhere,BUT are marketed using 35mm equivalent because that is what most people understand.

Old habits etc

[MickLL]

I know of NO camera that displays "equivalent focal length'. All the cameras and lenses that I know display only the actual focal length.

Konica Minolta A2 in front of me has a zoom of 7.2 - 50.8 actual and also says 28 - 200 (Equiv. 135).

I said that I wasn't an expert.

I stand corrected.

MickLL

[Roy5051]

Strictly speaking, of course, the "correct" standard focal length for the 35mm frame is 43mm (the length of the diagonal) and this type of measurement is used on most other film formats.

So, should you be looking for a 28mm lens (equivalent 42mm [or 45mm on Canon])?

Sorry - just had to confuse the issue!!!

[El_Sid]

Then I read in John Hedgcoe's "new manual of photography" that most lenses designed for digital SLRs quote focal lengths already converted to 35mm- equivalents.
So the question is- am I looking for a lens that says "50mm" on it, or "35mm"????

Any help greatly appreciated. I feel I'm going mad here...

Kev

To the best of my knowledge all the lenses manufactured specifically for crop frame DSLR's are marked with the actual focal length. I honestly cannot think of any maker that does otherwise; I have 5 crop frame lenses from 3 different makers and all are marked with the true focal length. Since APS-C format camera come with some minor variation in crop factor (Sigma are 1.7x, Canon 1.6x and the rest 1.5x) and 4/3rd format are 2x any attempt to mark the lenses with a 'corrected' focal length, espcially those from independent makers, would cause too much confusion.

As far as a 'standard' lens for APS format DSLR's is concerned there's no exact equivalent to the 50mm lens for 35mm cameras. The closest is Sigma's 30mm f1.4 which approximates to a 45 to 51mm equivalent depending on crop factor involved. Otherwise the poular choices tend to be either 28mm or 35mm full frame lenses according to personal preference - I use a 28mm myself.

I must say I'm surprised that John H would make such a strange statement...

[nspur]

Strictly speaking, of course, the "correct" standard focal length for the 35mm frame is 43mm (the length of the diagonal)

It may be, but the focal length to match the average human eye is 58mm and the human eye's approximate field of view is equal to a 33mm lens.

[TimF]

Then I read in John Hedgcoe's "new manual of photography" that most lenses designed for digital SLRs quote focal lengths already converted to 35mm- equivalents.

That is a weird sentence; I wonder if some sub-editor/work experience guy got at it. [img]/forums/images/graemlins/tongue.gif[/img]

[beejaybee]

but the focal length to match the average human eye is 58mm and the human eye's approximate field of view is equal to a 33mm lens.

Eh ... doesn't that statement contradict itself?

Nothing to do with "standard" lenses but with full-frame cameras I struggle visualizing with a 28mm lens - the scenes I visualize all come out needing a wider or narrow field of view. 24mm or 35mm work for me, 28mm doesn't. My issue, not the lens.

A "standard" lens has a focal length equal to the frame diagonal. Now some people find they prefer a shorter lens than that, some people prefer longer. It's a matter of taste as much as anything else.

May compact fixed lens 35mm format cameras had lenses in the near vicinity of 40mm focal length. Allowing for the film gate being slightly smaller than 24mm x 36mm this is very close to the diagonal. The 50mm lens which used to be considered "standard" with film SLRs came from this being the shortest focal length which didn't need retrofocus design in order to accomodate the mirror box, therefore could be made cheap, wide aperture & reasonably high quality, all of which were selling points at the time. A camera which came with a 40mm f/2.8 lens as "standard" would have difficulty selling against a similar price, similar quality camera with a 50mm f/1.8 lens, in the same way that a 10 MP camera now has difficulty competing against a 15 MP camera, even though it may be technically superior.

[RogerMac]

Then I read in John Hedgcoe's "new manual of photography" that most lenses designed for digital SLRs quote focal lengths already converted to 35mm- equivalents.
So the question is- am I looking for a lens that says "50mm" on it, or "35mm"????

Any help greatly appreciated. I feel I'm going mad here...

Kev

To the best of my knowledge all the lenses manufactured specifically for crop frame DSLR's are marked with the actual focal length. I honestly cannot think of any maker that does otherwise; I have 5 crop frame lenses from 3 different makers and all are marked with the true focal length. Since APS-C format camera come with some minor variation in crop factor (Sigma are 1.7x, Canon 1.6x and the rest 1.5x) and 4/3rd format are 2x any attempt to mark the lenses with a 'corrected' focal length, espcially those from independent makers, would cause too much confusion.

As far as a 'standard' lens for APS format DSLR's is concerned there's no exact equivalent to the 50mm lens for 35mm cameras. The closest is Sigma's 30mm f1.4 which approximates to a 45 to 51mm equivalent depending on crop factor involved. Otherwise the poular choices tend to be either 28mm or 35mm full frame lenses according to personal preference - I use a 28mm myself.

I must say I'm surprised that John H would make such a strange statement...

Some manufacturers cover all bases by printing both sets of focal length



Edit: The blue label is only stick on so I could remove it if I wanted


Roger