30mm designed for APS-C or 24mm designed for Full Frame?

So there's going to a alot of technical talk. So I've been having my eyes on the Samyang 24mm t1.5 cine lens for a long time now. It seems to have all the qualities I need. Wide aperture and the focal lenght are the most important of these as well as the sharpness. But I think I have found a better lens, the Sigma 30mm F1.4. The sharpness of this lens would give me about two more perceptual megapixels and it also works better wide open.

But here's the thing. Samyangs focal lenght is 24mm whereas Sigmas is 30mm. But the Sigma is designed for crop sensor cameras, so does it take in to account the field of view? Since the full frame Samyang would be really a 36mm on my D3200 and as stated the field of view is important.

So do APS-C designed lenses have wider angles of view than full frame designed ones on crop cameras?
If so, this would be all around better deal. Sigma is cheaper and has more functions than the Samyang.

Nope, even though the Sigma is designed for a crop sensor APS-C body, the focal length is still the focal length and does not identify the change in field of view. That 30mm Sigma will have an effective focal length of 45mmc where the 24mm Samyangs will be closer to 36mm as you mentioned.


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Alright. Even though the Sigma would be technically better, I have to go with the Samyang. I just need the extra field of view. Plus the focus ring is much better for video.

Do you shoot cine wide open? If not, try the kit 18-55. I have got decent movies with this lens, and the plus side is that you can also zoom in while shooting.

I have the kit lens. It's ok but it's only turly sharp at 18mm f/5.6, and even at it's sweet spot it only gives out about 7 perceptual megapixels of detail. And yes I need to shoot at at least f/2 since I'd be shooting indoors and outside in low light.