View of the Drew | Andrew Halpern Photography

Sick

IMG_3928-2

1/100″ F6.3 18mm (29mm equiv)

Manhattan Bridge

Yeah, it’s sick how people can deface bridges. There’s a pretty big difference between the way the Manhattan Bridge is taken care of, and that of the Brooklyn Bridge. There isn’t much to discuss with this shot, except for the fact I wish I had a wider lens. So, I’ll take the time to discuss how “crop factors” affect your photography.

You might have noticed under the settings, I’ll sometimes list two focal lengths. The first is the actual focal length my lens used. The second is the equivalent focal length in 35mm adjusted for my camera’s 1.6x crop factor.

Wtf is a crop factor you might ask? The concept traces its lineage to standard 35mm film cameras. The size of the 35mm negative became such a standard that we still use it today to reference digital cameras.  Remember with a digital camera, the sensor corresponds to the film.

If the sensor size matches that of a 35mm film negative, the camera is known as a “full-frame camera.” These are often quite expensive. Cheaper DSLRs (like mine) use smaller sensors known as APS-C.

The size of the sensor is important because combined with the focal length of the lens, it yields a specific angle of view.

744px-Full-frame_vs_APS-C-w

This diagram taken from Wikipedia, shows how a 50mm lens compares on different sensor sizes.

What this means is that for a given focal length, say 50mm, the angle of view (how close-up or far away the scene looks) will be quite different for different cameras. This is why it helps to use the “full-frame standard”.

In order to compare focal lengths on cameras with different sensor sizes, we can use the “crop factor”. To compare, just multiply the actual focal length of the lens by your camera’s crop factor.  For example, my camera has a crop factor of 1.6x. So if I put a 50mm lens on my camera, it gives an equivalent view as if I put an 80mm lens on a full-frame camera (50×1.6=80).

The crop factor can also be used to gauge how depth of field can compare on different cameras. Just multiply the crop factor by the aperture. For example, f/2 on my camera would correspond to an equivalent depth of field of f/3.2 on a full-frame camera.

This is precisely the reason why cameras with very small sensors (point and shoots) have difficulty getting the lovely background blur that’s capable with DSLRs. The crop factor for these cameras might be something like 5.6x. A lens that’s F/2.0 on that camera would give the equivalent depth of field of f/11.2. There’s not much creative flexibility in that case.

I hope that explains things somewhat. It’s a bit of a complicated topic.

Sensor Crop Factor
Samsung Galaxy S4 7.32
iPhone 5S 7.21
Digital Compact Cameras Anywhere from  6.0 – 4.0
Nikon 1 Series (Mirrorless) 2.72
Four-Thirds / Micro Four-Thirds
(Olympus, Panasonic system cameras)
2.0
Canon EF-S, (APS-C)      [My Camera] 1.6
Nikon/Pentax/Samsung/Sony (APS-C) 1.5
35mm film or Full-Frame any manufacturer 1.0
Medium Format Camera 0.65

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