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Back in the days when celluloid photography was all the rage, a 50mm lens was supposed to coincide with human vision. What is the equivalent with digital photography?

2007-03-17 04:59:01 · 5 answers · asked by tuthutop 2 in Consumer Electronics Cameras

5 answers

To achieve a 50mm field of view with a digital SLR, you need to take the cameras focal length multiplier into account (which tells you how much smaller the sensor is vs. a frame of 35mm film).
Nikon, Penax, Fuji, Samsung and Sony dSLR bodies all have a 1.5 multiplier, so you get 50mm with 50/1.5= 33.3mm lens. Say a 35mm lens.
With Canon, some models have a full frame sensor, so you can keep using a 50mm lens; some models have 1.3 flm, so you need to use about a 35mm lens; and some models (like the Rebels and the 30D) have a 1.6 flm, so you'd want a 30mm lens (Sigma makes a nice f/1.4 version).
Olympus has a multiplier of 2, so use about a 24mm lens.

2007-03-17 07:09:42 · answer #1 · answered by OMG, I ♥ PONIES!!1 7 · 1 0

Perfect answer, OMG, and you deserve "best answer" honors. I would assume that tuthutop is inquiring about a dSLR lens, because you don't really have a choice in point and shoot camera, but this opens up the possibility for some consideration of the "normal" lens on other cameras.

I don't know where else to put this, so for the trivially inclined, may I offer the following...

The actual "normal" lens is determined by the diameter of the field relative to the size of the film. A lens has a circular field, as we discussed in another question recently. The "normal" lens would have a focal length equal to the diagonal frame size, if the frame size was a square. Otherwise, the "normal" lens would have a focal length equal to the diagonal that would exist if only the frame was square.

In 6x6 square (60 cm x 60 cm; 2¼" x 2¼"), the diagonal is 84.85 millimeters, hence the normal lens is accepted as 85 mm. Hasselblad, Rollei and Mamiya call 80 mm "normal." Close enough.

In 35 mm film, the long side of the frame is 36 mm. The diagonal of a 36x36 square would be 51 mm, so 50 mm is pretty close. I remember makers in the 60's who called 55 mm normal.

In digital cameras there are many different size sensors, so there are many different "normal" lenses.

OMG has given the perfect answer for most Nikon and Canon digital SLR's, so I won't belabor the point. You can do the math yourself, if you are terminally curious.

The other two major sensor sizes in digital photography are called the 1/1.8" and 1/2.5". I have no idea how to EXPLAIN those designations, but the actual dimensions are about 7.2 mm x 5.3 mm for the 1/1.8" sensor and they are about 5 x 4 mm for the 1/2.5" sensor.

Doing the math, I find that the "normal" focal length for these cameras would be about 10 mm for the 1/1.8" and about 7 mm for the 1/2.5". Now maybe seeing "5.8-24 mm" on the front of a lens won't be so confusing to someone out there who cares. No wonder we can't get any Bokeh out of these cameras!

2007-03-17 11:37:51 · answer #2 · answered by Picture Taker 7 · 0 0

The best portrait lens is a 85mm lens - even on a cropped camera. They are very sharp lenses and usually have a good quality bokeh. Using one on a cropped camera means you have to backup a bit, but that inconvenience is still worth the result. The thing you can do though is to use your 18-55mm kit lens. Set it at 35mm and put a rubber band around the zoom ring so it is not easily moved (when bumped, etc) and go around for a day shooting the lens at that focal length. Then do the same thing at 50mm. You will then find out if you have to back up excessively or not; and then you will know what the best lens for you is. One thing though, you will not get a lot of out-of-focus range @ 35mm, and even at 50mm, it is not that great as you may still have to backup when taking photos - which increases the Depth-of-Field. But you will still get a good idea of which lens works for you by doing this simple test.

2016-03-16 21:59:45 · answer #3 · answered by Anonymous · 0 0

OMG and Dr. Sam, you deserve all the glory. Fortunately there aren't many guys like you two over at the spanish speaking versions of this forum.

Tuthutop, congratulations in looking for a prime lens for your digital camera. The kind of photography you can achieve with a prime has a completely different feel than what you can get with one of those slow zooms offered in cameras today.

Take care!

Ignacio

2007-03-17 16:53:51 · answer #4 · answered by Anonymous · 0 0

1

2017-02-09 16:04:17 · answer #5 · answered by Mike 4 · 0 0

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