Nx 50-150 is it really F4.2

Harleysoftail wrote:

Milondon15 wrote:

I have just bought the Samsung 50-150 for a great price but my excitement was slightly dampened after finding that F2.8 lens on APS-C is really equivalent to F4.2 full frame lens. Is this true?

This great article might help clarity things for you:

http://www.bobatkins.com/photography/tutorials/crop_sensor_cameras_and_lenses.html

If you read the paragraph under "Aperture" you will find the following answer "f2 is f2 is f2 and f8 is f8...period.

Hope this relieves your anxiety about your lens purchase because this is a GREAT lens.

I'm sure the linked article is great. But f2 is not f2 is not f2. That's the whole point. In SOME WAYS your f/2.8 is f/2.8 is f/2.8, and in SOME WAYS it is "just like" or "very similar to" f/4.2 on full frame... otherwise people wouldn't have invented the term "equivalent aperture".

Here's the whole story in as short a nutshell as possible. (I didn't read the article)

+ Your 50-150 2.8 will be "the same as" a 75-225 f/4.2 on full frame in the following sense: the field of view and depth of field will be precisely the same. (That's why they are "equivalent").

+ It is "different" in the sense that the PHOTONS PER UNIT AREA PER UNIT TIME is different. (say, 50 f/2.8 on APS-C or 75 f/4.2 on FF). It is the f-number that tells you the photons per unit area per unit time. This is the info you need (photons per unit area per unit time) to compute the exposure properly.

+ So if you compare a 50-150 f/2.8 on APS-C to a 75-225 f/4.2 on FF, the FOV and DOF will be precisely the same, but you will need to expose longer or increase the ISO on FF since you are at f/4.2. For "equivalent sensor technology" for fixed exposure time (say 1/60 second) increasing the ISO on the FF will give essentially the same image with the same noise.

+ (OPTIONAL READING) Of course a 75-225 f/2.8 on full frame will have a narrower DOF and less noise for the same exposure time since you are back down to the same ISO you were using on APS-C but one doesn't always WANT narrower DOF (I can rarely get two human faces in focus on APS-C at anything more open than f/2.8 unless I have people glued into a chair).

DONE.

Please no more discussions of equivalence

anywhere

ever

Go get the Samsung lens if you aren't worried about extinction of the NX line.  Full frame is overrated (Sony wants you to buy buy buy!!!).