I dont mean when for example 35mm on a crop sensor “equals” a 50mm on a full frame camera. My question is a bit weird, here we go.
So i have a 18-55mm lens (on a crop camera) and people say that 50-55mm is the focal length of the human eye. Here, my experiment comes into the play:
My camera has a 1.5x crop factor so 35mm looks like 50 mm on a full frame because of narrower field of view right? So when people say field of view of a 50mm on a full frame is the same as your eye, my first thought is 50mm on a full frame = 35mm on my camera. Then what i do is i take my camera put it on 35mm and then look at the vizor. What i expect is no zoom at all but the objects look smaller in the vizor (so fov is higher). When i put my camera at 55mm, the objects size match up with exactly what i see. But from what i learned 35mms should be like a 50mm on a full frame therefore it should match my eye.
So here comes my question:
Are the numbers of focal lengths on my lens already multiplier by 1.5x ? So do i have to subdivide the numbers to get the full frame equivalent ?
Sorry for spelling mistakes.
focal length should always be focal length (unless it’s labeled specifically as “equivalent focal length”)
nit pick here: people say a 50mm equivalent is the focal length of the human eye (and only some people… others will say 35mm… others have very different answers because the eye and brain do not perceive the world the same way a camera does… it’s an age old debate and doesn’t have an exact answer, I digress… I’ll come back to this at the end)
Yes
Your viewfinder itself has a magnification to it. Many cameras have a viewfinder with something like a 0.7x magnification, which shrinks the image to your eye. You’re not going to view the image on your viewfinder you’re going to view it on a monitor or as a print… keep that in mind.
Nope. If you take a 35mm lens made for your APS-C or a 35mm lens made for a full frame camera and put it on your camera… they’d have pretty much the same field of view.
Now here’s the other thing about field of view: Look straight in front of you. Hold your hands out to either side with your fingers stretched out and slowly swing your arms forward in an arch to move them so they’re in front of you. But do so slowly while looking straight ahead and keep moving your arms forward until you just start to see your hands come into your field of view. Odds are your arms are spread very wide… you’d nee a 10mm or so on your camera to photograph that wide an angle. But (assuming you still have your eyes straight forward and don’t turn to look at your hands) your fingers are going to be a blurry mush. We have very wide peripheral vision but cannot really see that sharply out that far. Keep moving your arms forward until you can start to see your fingers individually… that’s going to be a lot closer to that 35 or 50mm equivalent focal length. So the question of which focal length is “normal” really can’t answer the way the human eye sees, but it’s more about the area we tend to focus on in our day-to-day lives…
Oh, i understood the fov part and it makes more sense. The reason im asking this question is i want to buy a 200mm lens but should i look at videos of 300mm on a full frame or a 200mm ?
If you put a 200mm lens on your camera it will look like a 300mm lens on a “full frame” camera so if you look at videos, pay attention to the camera they’re using if they’re on a Canon 5D/R5 or Nikon D850/Z8 or Sony A7whatever, you’re going to want to see what 300mm can do in terms of field of view/zoom.
iow, normal is a natural representation of near -far objects. Our peripheral is way wide, but a spherical vs flat focal plane is a game changer. No comparison. On a flat plane, any lens that projects our field of vision in its entirety will inevitably lead to terrible near-far relationships with subjects.
Btw, I’ll never fly delta if you’re ever behind the sticks.
Near-far is perspective. That is purely controlled by distance of viewer-to-subject. Focal length (combined with sensor/frame-size) just chooses the angle of view (or “crop” if you want to think about it in how we see a wider field of view with our eyes) once you’re at that given distance/perspective.
I haven’t been at the yoke in over 20 years and that was only single engine props.