When is 50mm NOT 50mm?

slucc wrote:

I know when I buy a non-native lens for use on my NEX that I've got to multiply by 1.5. **BUT** when I buy a Sony E-mount lens do I still have to do the multiplication OR has Sony already figured that into the focal length? It's hard to believe that this hasn't been done, but then . . . I just don't know!

Silly question? ? ?

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Stephen Lucchetti

slucc wrote:

Definitely -- a 50mm lens is ALWAYS a 50mm lens -- that's physics. BUT, I guess the actual question should have been what is the effective focal length of the lens? When selling an E-mount lens is Sony quoting the actual focal length of the lens OR the effective focal length on their NEX system?

Is it really as simple as a 50mm lens is always a 50mm lens?

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Stephen Lucchetti

slucc wrote:

Definitely -- a 50mm lens is ALWAYS a 50mm lens -- that's physics. BUT, I guess the actual question should have been what is the effective focal length of the lens? When selling an E-mount lens is Sony quoting the actual focal length of the lens OR the effective focal length on their NEX system?

Is it really as simple as a 50mm lens is always a 50mm lens?

--
Stephen Lucchetti

slucc wrote:

I know when I buy a non-native lens for use on my NEX that I've got to multiply by 1.5. **BUT** when I buy a Sony E-mount lens do I still have to do the multiplication OR has Sony already figured that into the focal length? It's hard to believe that this hasn't been done, but then . . . I just don't know!

Silly question? ? ?

--
Stephen Lucchetti

zink wrote:

No, not a silly question. A lot of people are confused about this.

Focal length is an absolute number. A 50mm lens is a 50mm lens, on a NEX, on a full frame camera, or on whatever camera u use it. But the field of view will change on different sized sensors. When everybody used 35mm film, they called 50-60mm a standard lens, 40mm and below a wide angle, 60-105mm a short tele and everything above a long tele. On a NEX, with a 1.5 crop factor WHEN COMPARED TO 35mm FORMAT, you need to adjust this terminology. A 50mm on a NEX can not be considered a standard lens, because it behaves like a short tele on APS-C. So on a NEX, I would consider it like this:

Wide angle: 30mm and below

Standard: 30-40mm

Short tele: 40-70mm

Tele: 70mm or more

zink wrote:

No, not a silly question. A lot of people are confused about this.

Focal length is an absolute number. A 50mm lens is a 50mm lens, on a NEX, on a full frame camera, or on whatever camera u use it. But the field of view will change on different sized sensors. When everybody used 35mm film, they called 50-60mm a standard lens, 40mm and below a wide angle, 60-105mm a short tele and everything above a long tele. On a NEX, with a 1.5 crop factor WHEN COMPARED TO 35mm FORMAT, you need to adjust this terminology. A 50mm on a NEX can not be considered a standard lens, because it behaves like a short tele on APS-C. So on a NEX, I would consider it like this:

Wide angle: 30mm and below

Standard: 30-40mm

Short tele: 40-70mm

Tele: 70mm or more

kev777zero wrote:

What is considered wide or telephoto may be vary between photographers, but the consensus I got from here and most sites was that on full frame, <35mm is wide, 35-50(or even up to 60)mm is considered normal, 60-80mm is no man's land (hence rarely any full frame lenses were made using such FLs), 80-135mm is portrait(aka short tele), >135mm is telephoto.

why is 50mm on full frame normal? because 50mm is a human eye's focal length (maybe that's why it is easiest to make?), but what you see will not be exactly what you shoot if you used a 50mm, since when you are using a camera the lens is going to be closer to the subject than your eyes. Hence a lens ~45mm on full frame will be more ideal.

anyways taking into NEX's crop factor you divide my numbers above with 1.5, roughly giving:

wide: <23.5mm

normal: 23.5~33.5 or up to 40mm

no man's land: 40~53.5mm

portrait/short tele: 53.5~90mm

telephoto: >90mm

(I'm not exactly sure how the no man's land FLs came about, but I guess photographers just found it awkward as in it's hard to compose street shots or portraits with it)

50mm on NEX does make it a no-man land's FL, so your traditional photographer will be loathed in using it. However it's quite close to portrait and it's easy to make hence cheaper so the average shooter tends to accept it.

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http://www.flickr.com/photos/kevinwlyu/

kev777zero wrote:

why are people making it so confusing for the OP?

Put simply, ANY lens you put on NEX requires a x1.5 on the FL written on the lens.

No, not a silly question. A lot of people are confused about this.

Focal length is an absolute number. A 50mm lens is a 50mm lens, on a NEX, on a full frame camera, or on whatever camera you use it. But the field of view will change on different sized sensors. When everybody used 35mm film, they called 45-60mm a standard lens, 45mm and below a wide angle, 60-105mm a short tele and everything above a long tele. On a NEX, with a 1.5 crop factor WHEN COMPARED TO 35mm FORMAT, you need to adjust this terminology. A 50mm on a NEX can not be considered a standard lens, because it behaves like a short tele on APS-C. So on a NEX, I would consider it like this:

Wide angle: 30mm and below

Standard: 30-40mm

Short tele: 40-70mm

Long tele: 70mm or more

Lightshow wrote:

Because the focal length does not change, period.

Using a smaller sensor does nothing but crop the image circle from the lens, so it's the field of view that is changing, not the focal length, so using 1.5x the FL is an over simplification of what's happening.

blakninja wrote:

But let's say i take a photo with nex using a 50mm and take a photo with FF cam using a 75mm lens, and i frame it exactly the same, will i get a similar image composition? I think NOT, right?

zink wrote:

Who is making it difficult now for the OP? Also, with zoom lenses, there is no "no man's land".

yes actually you will. the FOV will be the same in your example

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http://www.daisyseyecancerfund.org/Files/Awareness/photographing_rb_poster.pdf