Posted by Jay Ryser on December 13, 2007 at 3:08 PM
Pardon me if this question has been asked before, but I'm wondering about the crop factor with DSLRs.
Obviously, with the crop factor, wide angle lenses aren't so wide anymore, but does that really translate into an increased telephoto effect?
In other words, does a 1.5 crop factor on a 400mm lens (for instance) give you just the FIELD OF VIEW of a 600mm lens, or does it actually increase the magnification factor to the equivalent of 600mm?
Posted by David Bostedo on December 13, 2007 at 3:43 PM
I have to say, I'm not sure what you mean when you ask if it's the magnification factor Jay....
But it's actually a field of view difference - the same as if you had a physically larger sensor and just cropped the center part of the image out of it. The actual number of pixels in this area may vary, but it's the same conceptually.
Posted by Basil Greber on December 13, 2007 at 3:48 PM
You usually have higher pixel density on the small sensors, so I'd say the answer to your question is yes, even though I'm not completely sure that I understand it.
It only affects your field of view, not your magnification. So a 100mm lens with have the "magnification" power of a normal 100mm lens, but will have the field of view equivalent of 150mm.
Try this site for a more detailed explination
<html> http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm </html>
also
<html> http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml </html>
Posted by David Bostedo on December 13, 2007 at 4:29 PM
OK, I think I get the question now...good post Aleksei.
Simply put (I hope) :
-- Magnification factor is a property of the lens and lens distance from the sensor. It doesn't change unless the distance from the sensor changes (which would also change the focus distance, etc.
-- Crop factor is a property of the sensor caused by the sensor being smaller than 35mm. It changes the field of view for any 35mm lens.
-- Using a 35mm lens, you get the same image circle at the same magnification factor, but you record and see a much smaller portion of it, which changes the field of view.
-- If you make two print of the same size, one from 35mm and one from a cropped sensor, you may appear to have a larger magnification factor - but only due to the cropped field of view.
Hope that makes sense as a summary...
Posted by Jay Ryser on December 13, 2007 at 5:01 PM
Sorry to not be clearer in my question.
A 1.5 crop factor doesn't actually turn a 400mm lens into a 600mm lens.
If we used the same 400mm lens on a DSLR with a full frame sensor and one with a 1.5 crop factor sensor, and compared images, the image from the cropped sensor wouldn't actually provide increased magnification as much as it would a smaller field of view version of the same image at the same magnification.
Does that make sense?
Posted by Jay Ryser on December 13, 2007 at 5:11 PM
Or to re-clarify (hopefully), is it a "magnification" factor, or just a "crop" factor?
It would be easier to understand if we made prints the size our our sensors, but we don't.
When you make the same size image from a smaller sensor it has been enlarged more. The lens did the same thing is always does, you just recorded a smaller area of the image it casts onto the focal plane. There is no magnification in the camera, it is pure crop.
Pete D.
Posted by Paul Skoczylas on December 13, 2007 at 7:10 PM
There's no such thing as a telephoto effect!
The ONLY thing that determines the relative size and position of objects in a picture is the position the picture was taken from. Lens length or crop factor are irrelevant.
What we call telephoto effect comes from the fact that when you use a long lens, you tend to stand further back--that's what creates the effect.
-Paul
Posted by Bill Chambers on December 13, 2007 at 9:44 PM
Think of it as the cropped sensor placing a cardboard cut-out (or mat) over a full frame image. Lift the mat off the image and you have full frame. The actual size of the subject matter in the center never changes, only the perception of size changes.
Paul Skoczylas has the right perspective. At least, that's the way I see it from here.
Pete D.
Posted by Steve Foss on December 14, 2007 at 12:02 AM
Well, as always when this topic comes up this is as clear as mud. As many times as this has been asked and answered on this and other online fora, you'd think there'd be a clear answer already given that one could link to. Conflicting points of view — and a wide variety in clarity of thinking and written expression — make this as simple as the U.S. tax code.
I'll just keep shooting what I've got and trying as hard as I can to turn my vision into art and leave the tax code to all you tax lawyers.
Posted by Paul DeCesare on December 14, 2007 at 1:22 AM
I think it can be answered clearly... no, Jay, the magnification does not increase. A 200mm lens on a 1.5 crop camera 'appears' to shoot like a 300mm, but you don't get that wonderful background compression of a 300mm lens. You still get 200mm compression, because that's the lens you are using. It just gets cropped, period. On my full frame 5D, if I use a 200mm lens, then crop the shot a third, I'll have the same image as the 1.5x camera in look and feel. Probably less pixels, but same look and feel.
Hope that helps!
Posted by Basil Greber on December 14, 2007 at 1:48 AM
Ok... clear as mud sums it up nicely, Steve. I don't quite get what we're talking about. There's the crop factor - which is obviously 1.5x. Then there's the reproduction ratio - which intrinsically is defined via sensor size, so that cancels out, and a 1:1 macro will be a 1:1 macro also on a cropped sensor (even though it will allow tighter compositions). Now, what's "magnification factor" exactly? Then, Paul brings up the topic of DoF (which is larger for the same composition when using the same lens on a 1.5x crop sensor than on a full frame sensor). Then there's perspective compression - where I have no clue what happens.
Leonardo Da Vinci would answer that it is the PERSPECTIVE. Take a look at The Last Supper. I don't know if PeteD above was giving us a pun, but while the subject size may be the same when using a camera with a crop factor of 1.5 versus a a full frame camera, the relationship between the background, foreground and subject will be different. Thus, the perspective is different.
Posted by Paul Skoczylas on December 14, 2007 at 11:14 AM
David, simply changing the crop factor does NOT change the perspective. Now if you moved further back to get the same subject size with the cropped camera, *that* would change the perspective. But if you changed focal length by the same proportion to get the same subject size without changing your position, the perspective would not change.
I'll repeat what I said before, in different words: the *only* thing that affects perspective is the position the camera was in relative to the scene. Anything you change at the camera (focal length, crop factor) has absolutely no effect on perspective. If you move the camera, you change the perspective.
As the treads state, the mm is the same no what type of focal length of lens you're using. I did an experiment where I shot the same image using the 18-70mm kit lens that came with my D70S and a Nikon 70-300mm lens. I shot the image at 70mm on both lenses. The 18-70mm lens is made for Nikon DSLRs only and is made to fit the smaller sensor. The 70-300mm can be used on either the smaller or full frame sensors or 35mm. The appearance of maginification comes when you look at the image in Bridge or Photoshop. The image shot with the 70-300mm lens was cropped to fit the smaller sensor but was increased 1.5x to filled the 3008 x 2000 pixel area. This gives the appearance of maginification.
Posted by David Bostedo on December 26, 2007 at 10:44 PM
Wow...this is a confusing thread. Boris - I don't think your explanation is quite correct (but I may be reading it wrong).
There is no "increase" of 1.5x. Instead, the smaller sensor only captured 66% of the 70mm full frame image (that would have been captured with 35mm film). This gives the same field of view as a 105mm lens on a 35 mm camera. That's where the 1.5x comes in - in what field of view the camera sees, not in any type of enlargement or increase in the image. The image at the sensor is the same, and a smaller portion of it is recorded.
You're right about Bridge or PS - using these to look at a 35mm image, and a D70S image taken from the same spot with the same actual focal length (70 mm in this case) at the same screen size will mean that the view is "zoomed in" for the D70S image. This is regardless of the number of pixels - only the sensor size matters.
Here's some more mud to through on this one. Let's compare a full size sensor to a 1:6 crop, both having 10 megapixels and using the same 200mmm lens. Now the larger sensor will capture a bigger image since it has a larger field of view compared to the smaller sensor. However, because the smaller sensor has a higher density of pixels (remember its 10 megapixels are packed into the smaller space) you can blow up the image more than the one from the larger sensor and in effect get greater magnification without pixelation.
Discussion
19 repliesObviously, with the crop factor, wide angle lenses aren't so wide anymore, but does that really translate into an increased telephoto effect?
In other words, does a 1.5 crop factor on a 400mm lens (for instance) give you just the FIELD OF VIEW of a 600mm lens, or does it actually increase the magnification factor to the equivalent of 600mm?
But it's actually a field of view difference - the same as if you had a physically larger sensor and just cropped the center part of the image out of it. The actual number of pixels in this area may vary, but it's the same conceptually.
Basil
It only affects your field of view, not your magnification. So a 100mm lens with have the "magnification" power of a normal 100mm lens, but will have the field of view equivalent of 150mm.
Try this site for a more detailed explination
<html> http://www.cambridgeincolour.com/tutorials/digital-camera-sensor-size.htm </html>
also
<html> http://www.luminous-landscape.com/tutorials/understanding-series/dslr-mag.shtml </html>
Simply put (I hope) :
-- Magnification factor is a property of the lens and lens distance from the sensor. It doesn't change unless the distance from the sensor changes (which would also change the focus distance, etc.
-- Crop factor is a property of the sensor caused by the sensor being smaller than 35mm. It changes the field of view for any 35mm lens.
-- Using a 35mm lens, you get the same image circle at the same magnification factor, but you record and see a much smaller portion of it, which changes the field of view.
-- If you make two print of the same size, one from 35mm and one from a cropped sensor, you may appear to have a larger magnification factor - but only due to the cropped field of view.
Hope that makes sense as a summary...
A 1.5 crop factor doesn't actually turn a 400mm lens into a 600mm lens.
If we used the same 400mm lens on a DSLR with a full frame sensor and one with a 1.5 crop factor sensor, and compared images, the image from the cropped sensor wouldn't actually provide increased magnification as much as it would a smaller field of view version of the same image at the same magnification.
Does that make sense?
When you make the same size image from a smaller sensor it has been enlarged more. The lens did the same thing is always does, you just recorded a smaller area of the image it casts onto the focal plane. There is no magnification in the camera, it is pure crop.
Pete D.
The ONLY thing that determines the relative size and position of objects in a picture is the position the picture was taken from. Lens length or crop factor are irrelevant.
What we call telephoto effect comes from the fact that when you use a long lens, you tend to stand further back--that's what creates the effect.
-Paul
Pete D.
I'll just keep shooting what I've got and trying as hard as I can to turn my vision into art and leave the tax code to all you tax lawyers.
Hope that helps!
Basil
I'll repeat what I said before, in different words: the *only* thing that affects perspective is the position the camera was in relative to the scene. Anything you change at the camera (focal length, crop factor) has absolutely no effect on perspective. If you move the camera, you change the perspective.
-Paul
There is no "increase" of 1.5x. Instead, the smaller sensor only captured 66% of the 70mm full frame image (that would have been captured with 35mm film). This gives the same field of view as a 105mm lens on a 35 mm camera. That's where the 1.5x comes in - in what field of view the camera sees, not in any type of enlargement or increase in the image. The image at the sensor is the same, and a smaller portion of it is recorded.
You're right about Bridge or PS - using these to look at a 35mm image, and a D70S image taken from the same spot with the same actual focal length (70 mm in this case) at the same screen size will mean that the view is "zoomed in" for the D70S image. This is regardless of the number of pixels - only the sensor size matters.