Crop Sensor vs. Full Frame and lens focal lengths

Can't answer all your questions, but in the case of a 7D/T2i/T3i/whatever, the crop factor is 1.6x. So on a full frame, a 50mm is a true 50mm. And to answer your specific question, a 16mm would look like a true 16mm on a FF, but if you put it on a crop sensor then it would look more like how a ~25-26mm would look on a FF (16x1.6).

Thanks Will that definitely helps.  Still would like to learn as much as possible so I'm not making stupid lens purchases that give me the look that I don't want.

I really liked the look at 16mm on my D7000 and I'd like to get a prime for my D600 that would be similar so I'm assuming a 24mm or 28mm prime would be close, maybe???

yes, 16 on FF is an ultra wide

that's correct. for nikon, if the lens is FF, you will have to account for the 1.5x crop when putting it on a DX body. So if you have a 50mm FF prime, it's actually like using an 85mm on a FF body. However, if you're using a DX lens (ex 35mm F/1.8G DX), then the crop is already accounted for, so it's the same as using a 50mm FF on a FF body.

Huh? I have a Nikkor 50mm 1.8.  So that will actually be 50mm on my D600 but on my D7000 it's around 80mm.  That's what your trying to say right?  That I understand.  So the look of what my 50mm did on my D7000 would be comparable to an 85mm lens on a FF.

What? Pretty sure that's wrong.....

i thought for the longest time when a lens said "APS-C" it was a correct focal length, then i finally tested my 50 1.8 EF against my 18-55 EFS and my Tamron 17-50. so yes, you ALWAYS need to use the crop factor.

someone tell me if i'm retarded and fucked that test up too, i need to know these things.

dx (cropped) lenses are true to their focal length, and so are fx (full frame) lenses

So I just tested my 16-85 DX vs my 50mm f/1.4D FF with my 16-85mm at 50mm on my D7000. They aren't the same. The 50mm prime is substantially more telephoto. I'm pretty sure what I said or meant to say in my original statement is correct. At 50mm with a DX lens, it's the same as 85mm with a FF lens on a FX body.
So then a 35mm DX lens must be the same as a 50mm FF lens on a FX body, RIGHT!?!?

i thought i had this figured out until fucking ns comes along, can someone confirm or prove me wrong here please?

I meant to say when using those DX lenses on a DX body, not both lenses on a FX body.

must be a different setup between canon and nikon then

Okay to clear the confusion here, a few people are confused about lens conversions from FX and DX. All lenses are the same focal length, however with the smaller sensor size of the DX the converging light that flips from the lens (your sensor sees upside down) allows for less coverage. The ratio from FX to DX is 1:1.5 which means that a 50mm on FX is its own angle, but the equivalent of that same 50mm lens on a DX sensor would be a 75mm lens on FX. This makes telephotos zoom in farther on DX (ex a 200mm lens on DX would be like having a 350mm on FX) but FX allows wider angles. That's why most FX wide angles are about 24mm but on DX the lenses are about 18mm. If you use a proper 18mm lens on FX it is super wide. The inverse is true from DX to FX with the ratio being 1:0.66. Hope that truly answers the question!!

nope not true at all. Not sure where you've heard this but it's 110% false

ALL lenses are measured at a 35mm AKA FULL FRAME equivalent. It's simply the FOV that changes, not the measurement, even for APS-C/DX specific lenses.


Here's an image of 35mm full frame, and the equivalent FOV you'd get IF YOU WERE TO USE THE SAME LENS on a:
Green: 1.3x APS-H 1D body
Red: 1.5x Nikon DX body
Blue: 1.6x Canon APS-C body

This is wrong.

DX lenses are NOT the correct focal length, you still have to account for the crop factor regardless of whether it's a DX of FX lens. It's a common misconception that I also believed but my manager at work (camera store) told me otherwise.

This is a helpful tool in showing you what the various focal lengths look like on different camera bodies, you can keep different combinations of cameras and lenses and quickly switch between them to see the differences, and also shows the field of view in degrees. My advice is to just play around with this and see what you like.

http://imaging.nikon.com/lineup/lens/simulator/index.htm

That was painful to read.  I liked the diagram!

Relevant info, about many crop vs. full frame comparisons: http://www.graphic-fusion.com/fullframe.htm#widetele

"Probably the biggest difference one will notice between FF and APS-C is the behavior of one's full frame lenses. When a FF lens is mounted on an APS-C camera, only a portion of the image circle is used, and the angle of view is therefore not as wide. A FF camera opens up all of the wide-angle potential of a FF lens. There is also a bit of difference in lens availability on the wide end for FF vs. APS-C. Although manufacturers have expanded their APS-C lens lines to include some extraordinarily wide angle coverage in both formats (e.g. Sigma's FF 12-24 and their largely equivalent APS-C 8-16), there are still far more lenses that will render a wide angle of view on FF cameras than on APS-C cameras. This will logically continue to be the case until such time as the APS-C wide angle offerings exceed the FF offerings by a considerable margin. If you are considering jumping into the APS-C format, just be careful that the more limited wide angle offerings are to your suiting."

Cameras with different sizes of sensors all still use the same focal length measurement. Focal length is a physical property of a lens, and is not the only factor in the field of view of an image.

For example, for a smaller-sensor sized camera (let's say Canon Powershot SD1400 IS, http://www.canon.ca/inetCA/products?m=gp&pid=3513#_030), the focal length at the wide end of the zoom range is 5.0mm. For this camera, the FOV is a full-frame equivalent to 28mm (meaning that it is the same FOV as if you put a 28mm lens on a full-frame body). To get the full-frame equivaent FOV of 28mm on a crop (1.6x) body, the required focal length is 28/1.6=17.5mm.

No SLR lenses, to my knowledge, rate the lens in terms of equivalent (35mm) focal length.