Quick noob perspective question

[Ronaldo]

So I'm a little confused about something.

I know that a 50mm lens is the "standard" lens on a 35mm and full-frame camera (e.g., Nikon D700).

And that a 35mm lens is the "standard" lens on certain crop frame cameras (e.g., Nikon D90).

Further, on a full-frame camera a 35mm lens can also introduce "distortion", say of someone's nose in a portrait.

So here's my question: Does a 35mm lens on a crop frame camera also introduce the same distortion as that lens would on a full-frame camera? Or, since the sensor is smaller is the 35mm lens on a crop frame camera really like a 50mm lens on a full-frame camera (i.e., is it truly a standard lens)?

Hope this makes sense.

thanks

 

[o hey tyler]

Prime lenses often are superior when it comes to distortion. You'll find that wide-medium zoom lenses have more distortion.

On an FX body, if you're shooting with a 50mm f/1.4 wide open, you'll see minor vignetting around the edge of the frame because of the way the light enters the optics. Yet on a DX body, the vignetted area is out of your FoV (or is less noticeable when shooting wide open). I could be wrong, but as far as I know what I said was accurate. If anyone has any other points, or corrections I'm sure they'll interject.

I have a T1i (Cropped body) and a 5D (full frame) along with a 50mm f/1.4 and a 35mm f/2. Maybe I'll set up some tests since I have the necessary equipment at my disposal.

As far as distortion is concerned, I think it would be roughly the same between lenses. There are lens profiles that you can select in CameraRAW to correct the distortion of particular lenses.

 

[Big Mike]

The lens projects an image (image circle) behind it. The lens isn't really concerned about the size of the sensor in the camera behind it. The only difference is that a 'crop' body doesn't see the whole image circle projected by 'full frame' lenses.

So if that 35mm lens shows some distortion, then it will be present on either a crop or full frame camera.

But that being said, distortion is often much worse at the edges of the image circle...and that is the area that is cropped off by the smaller sensor, so the overall image may have less distortion on a crop body compared to a full frame body.

 

[enzodm]

So I'm a little confused about something.

I know that a 50mm lens is the "standard" lens on a 35mm and full-frame camera (e.g., Nikon D700).

And that a 35mm lens is the "standard" lens on certain crop frame cameras (e.g., Nikon D90).

Further, on a full-frame camera a 35mm lens can also introduce "distortion", say of someone's nose in a portrait.

So here's my question: Does a 35mm lens on a crop frame camera also introduce the same distortion as that lens would on a full-frame camera? Or, since the sensor is smaller is the 35mm lens on a crop frame camera really like a 50mm lens on a full-frame camera (i.e., is it truly a standard lens)?

Hope this makes sense.

thanks

I asked myself the same question and, although not fully convinced, I found useful this page: Focal length and Perspective

The nose effect is caused by perspective more than lens distortion - at least this is what I think I have understood. Crop body simply crops, so perspective should be the same.

 

[Ronaldo]

I asked myself the same question and, although not fully convinced, I found useful this page: Focal length and Perspective

The nose effect is caused by perspective more than lens distortion - at least this is what I think I have understood. Crop body simply crops, so perspective should be the same.

Yeah - - maybe I phrased/asked this wrong. Here's an example of the perspective/distortion that I'm talking about:

http://barbgordonphotocoach.com/blog/wp-content/uploads/2010/02/BGPCEILessonFive1-300x200.jpg

And I was wondering if this is strictly a lens and distance issue, or if the crop sensor had any impact on this.

So for a certain amount of perspective-distortion that one would get on a 35mm lens on a full-frame body at a certain distance, would that "nose" distortion be the same on a crop frame - - even if because of the cropping the 35mm lens on the crop body is the "standard" lens??

I hope I'm not just making this more confusing. . .

 

[Big Mike]

That is mostly a result of the distance to the subject. Now of course, with a wider lens, you have to get closer to the subject, in order to fill the frame (get the same composition)....so that is where the difference comes in.

If you didn't move closer when you switched to a wider/shorter lens. The perspective/distortion should be the same...you would just have more of the background in the frame.

 

[Ronaldo]

That is mostly a result of the distance to the subject. Now of course, with a wider lens, you have to get closer to the subject, in order to fill the frame (get the same composition)....so that is where the difference comes in.

If you didn't move closer when you switched to a wider/shorter lens. The perspective/distortion should be the same...you would just have more of the background in the frame.

Thanks, I think I almost have it.

But with the crop sensor, would you have to move closer to the subject?

For example, let's say you were standing 10' from a subject with a 50mm lens on a Nikon D700. And you like the composition, distortion, etc.

Now, without moving you put down the D700 and picked up a D90 with a 35mm lens.

Would the picture contain (roughly) the same subject area and composition - - and would the perspective-distortion also be (roughly) the same??

 

[enzodm]

I found another useful thread (for me too): http://www.thephotoforum.com/forum/...rence-between-full-frame-cropped-sensors.html

 

[Big Mike]

For example, let's say you were standing 10' from a subject with a 50mm lens on a Nikon D700. And you like the composition, distortion, etc.

Now, without moving you put down the D700 and picked up a D90 with a 35mm lens.

Would the picture contain (roughly) the same subject area and composition - - and would the perspective-distortion also be (roughly) the same??

I don't want to fully commit to this answer...as it's Monday...but to my understanding. The perspective would be the same, because you are still the same distance away. But because you changed the lens, the distortion may be different.

 

[djacobox372]

The "distortion" the TS is referring to (nose appearing bigger then it really is), is not related to the lens, but instead it's related to the distance from the camera to the subject, which exaggerates the foreshortening effect of perspective.

A 35mm lens will have the same distortion on both full-frame and crop, but with full-frame you may need to move closer to the subject to achieve the same composition, since 35mm is wider on full frame. The closeness to the subject is what causes the distortion not the lens; if you use a 50mm lens on full-frame you can stand in about the same spot you would with 35mm on a crop sensor camera and achieve the same composition--and the distortion would be the same.

Make sense?

ps. lens distortion as it refers to lens performance is NOT what the TS is talking about, but he's probably really confused now due to all the answers relating to that topic.

 

[Ronaldo]

The "distortion" the TS is referring to (nose appearing bigger then it really is), is not related to the lens, but instead it's related to the distance from the camera to the subject, which exaggerates the foreshortening effect of perspective.

A 35mm lens will have the same distortion on both full-frame and crop, but with full-frame you may need to move closer to the subject to achieve the same composition, since 35mm is wider on full frame. The closeness to the subject is what causes the distortion not the lens; if you use a 50mm lens on full-frame you can stand in about the same spot you would with 35mm on a crop sensor camera and achieve the same composition--and the distortion would be the same.

Make sense?

ps. lens distortion as it refers to lens performance is NOT what the TS is talking about, but he's probably really confused now due to all the answers relating to that topic.

Yes - - this is what I was looking for. thanks