DX Crop Factor
- Thread starter SkvLTD
- Start date
OK my question is then, if I was to get a 28mm f/1.8G (42mm equivalent in 35mm/FX world), would that be suitable for semi portrait type work on say my kids?
What I'm looking for is a wide(r) lens than my 50mm f/1.8G which allows me to stand closer to the kids and still get them both in, and still get that lovely rich bokeh
What I'm looking for is a wide(r) lens than my 50mm f/1.8G which allows me to stand closer to the kids and still get them both in, and still get that lovely rich bokeh
BackdoorArts
Senior Member
Look at the faces in the 16mm and 35mm close-up photos above, and compare that to how they look at 50mm and 85mm. Stand close with a 28mm and you're going to get some distortion.
In one of Kelby's books, I think the first one Digital Photography, he has a nice page showing a portrait done with a 35mm lens. Basically it is a guy sitting in an arm chair in some sort of living room or study. The sitter occupies about a third to half of the frame to one side and the rest of the frame shows the interior of the room he is in. Basically Kelby says you can use a wide angle when and if you need to relate the subject to his or her surroundings or something to that effect.
You're really only going to get the distortion if you are close to the subject...
You're really only going to get the distortion if you are close to the subject...
I'm just thinking, that to get two heads or two head & shoulder shots etc from a wide angle perspective, will there be much distortion.
I have the 50mm f/1.8G and I often find I have to step too far back to get both kids into the frame, but if I got the 28mm f/1.8G that wouldn't be an issue
I have the 50mm f/1.8G and I often find I have to step too far back to get both kids into the frame, but if I got the 28mm f/1.8G that wouldn't be an issue
BackdoorArts
Senior Member
You shoot a building with a 28mm and you will get distortion. It's the lens. With 2 faces you'll be further away, so the distortion will not be as radical, but it will be there. I am absolutely not saying you won't be able to take a nice photo of them - you will definitely be able to do that. I am saying that I would never use it in a portrait situation.
My understanding might be a little off, but I feel like we're having two separate discussions here: one on perspective and one on distortion. Distortion comes from the lens, and there's nothing you can do to change that before you take the shot. Perspective comes from where you're standing.
In BackDoorHippie's great example, the weird "carnival mirror" look to the girls face in the 16mm photo isn't coming from distortion in the lens; it's coming from the fact that the photographer has to stand inches away from the subject to fill the frame with her head at 16mm. The perspective is much closer than we would normally stand to someone, so it looks odd. Take a look at the far left 16mm photo (the head and shoulder shot). It looks much more normal, since the subject is now further away. The perspective is more natural.
I don't do a lot of portraits, but it's my understanding that the 105mm is a popular portrait lens because it lets you get a closer shot while still maintaining a normal distance from the subject, resulting a photo with a natural looking perspective.
I also think about it this way: Put identical 35mm lenses on an FX camera and a DX camera and take a photo with each where the subject fills exactly the same amount of the frame. The perspective will be different, since you'll have to stand farther away with the DX camera to get the subject to be the same size in the viewfinder. In that way, the 35mm on the DX will behave like a 50mm (52mm and some change I think if you're being exact) when it comes to angle of view. Distortion in both will be similar (not identical, since you'll lose some of the edges on DX). I've always found it pretty hard to pick out distortion though, unless it's really severe or the photo involves straight lines or perfect geometric shapes.
Hope this helps! Feel free to tighten me up if my concepts are off.
In BackDoorHippie's great example, the weird "carnival mirror" look to the girls face in the 16mm photo isn't coming from distortion in the lens; it's coming from the fact that the photographer has to stand inches away from the subject to fill the frame with her head at 16mm. The perspective is much closer than we would normally stand to someone, so it looks odd. Take a look at the far left 16mm photo (the head and shoulder shot). It looks much more normal, since the subject is now further away. The perspective is more natural.
I don't do a lot of portraits, but it's my understanding that the 105mm is a popular portrait lens because it lets you get a closer shot while still maintaining a normal distance from the subject, resulting a photo with a natural looking perspective.
I also think about it this way: Put identical 35mm lenses on an FX camera and a DX camera and take a photo with each where the subject fills exactly the same amount of the frame. The perspective will be different, since you'll have to stand farther away with the DX camera to get the subject to be the same size in the viewfinder. In that way, the 35mm on the DX will behave like a 50mm (52mm and some change I think if you're being exact) when it comes to angle of view. Distortion in both will be similar (not identical, since you'll lose some of the edges on DX). I've always found it pretty hard to pick out distortion though, unless it's really severe or the photo involves straight lines or perfect geometric shapes.
Hope this helps! Feel free to tighten me up if my concepts are off.
SkvLTD
Senior Member
And I totally didn't realize this, but it could help other newcomers like myself- when using FX lenses on DX bodies, the field of view will be x1.5. Didn't even realize this until I shot my 18-70 again and noticed that at 50mm its much wider than my 50mm, and no wonder.
So to all others thinking- I'll get FX glass while on DX thinking about the future, no go (to a degree). No wonder I felt that my old 50mm was a lil too zoomed in for a 50.
So to all others thinking- I'll get FX glass while on DX thinking about the future, no go (to a degree). No wonder I felt that my old 50mm was a lil too zoomed in for a 50.
No, no, no, the 50 of the 17-55 will give you the same view as your 50 FX lens. What probably happens is that your zoom markings that say 50 might not be exactly 50… The lens focal length does not change wether it's used on a DX or FX, it just sees larger on the FX.
SkvLTD
Senior Member
Then, that's very, very strange... but, just going by the physical throw of the zoom, the top end of 18-70, is 70, and the frame it captures is almost the same as my old pre-ai 50mm. At 50 mark or where 50 would be aka below the max zoom, it has a much wider viewing angle than the prime.
Math-wise, the numbers have that 1.5x in common, so I don't think its any kind of fault of either lens.
Looking at all the standard diagrams that show the difference, highlights that too. It was just, both interesting and a tad frustrating to notice visually.
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It is not out of whack but what you are experiencing is called focus breathing which is common to some zoom lenses such as the Nikon 70-200mm f2.8VRII. @200mm is a lot shorter than what is claimed.