Is the telephoto effect of a crop sensor real?

I know this has been discussed before, but is it really there? The actual subject size of the image falling on any sensor is the same for a given lens. You just get less coveage with a cropped sensor. The telephoto effect is achieved by enlarging the image. But why can't you just enlarge the image from a full frame sensor? My 5D Mark II, at 21 mega pixles, I would assume can be enlarged as much as a cropped sensor of lower total mega pixles to get the same "telephoto" effect.

If you were to crop roughly 36% off your full frame photo in Lightroom or Photoshop, it would be exactly the same framing as shooting with a crop sensor.

Though a bit different, I've experimented with this concept using my 200mm and cropping it to the same frame as a rented 300mm. Same camera, same scene, two different FLs. Though it worked to a certain extent, the difference became obvious when I tried to go large.
What you ask may or may not be similar, but it would be interesting to test it.
--

In the end, the only things that matter are the people we help and the people we hurt. http://pa.photoshelter.com/user/ronkruger

but it depends on the lens/FX-DX combination (using the Nikon designation).

the difference between a 400mm shot of a full frame and the same out of a 300mm on a DX (or cropped) will be minimal because the lenses are similar.

But a "classic" head&shoulder done with the 85mm on a FF will not give the same effect (compression and overall bokeh) of a 50mm on a DX because the distance will be different and mainly because the 50 is a standard focal intended for standard "views" that on a cropped sensor brings things closer but the rest of the "effect" of the 85mm will be missed.

That said one must shoot with what he has at the moment. For example when you use a tele-zoom (like the 70-200) the difference will also be minimal.

... taken with a 50mm lens on a full frame camera.

Take a pair of scissors, and one of the prints, and cut off a strip from each of the four sides.

Put the same lens on a so-called crop sensor camera, take the camera to the same place you made the photo above, and take a photo.

It will look just like the trimmed photo.

Blow up the second image to 8x12, using the entire image from the second shot. Place it beside the original full frame 8x12.

You will see the difference a sensor size makes.

BAK

hzmeyer said:

I know this has been discussed before, but is it really there? The actual subject size of the image falling on any sensor is the same for a given lens. You just get less coveage with a cropped sensor. The telephoto effect is achieved by enlarging the image. But why can't you just enlarge the image from a full frame sensor? My 5D Mark II, at 21 mega pixles, I would assume can be enlarged as much as a cropped sensor of lower total mega pixles to get the same "telephoto" effect.

Click to expand...

Yes, basically. Your 5D2 is just as good as an 8mp 20D for capturing distant detail. It doesn't come close to a 7D/60D/600D though. You would need to get closer or use a more powerful lens to do that.

--
Adam

Yes, sure it's real! What a question! If you believed 35-mm full-frame format was 'the real thing' and APS-C format or 4/3rds was some sort of 'fallacy' then what do you think is medium format? Or 8 × 10" view cameras?

mystic-bright said:

but it depends on the lens/FX-DX combination (using the Nikon designation).

the difference between a 400mm shot of a full frame and the same out of a 300mm on a DX (or cropped) will be minimal because the lenses are similar.

But a "classic" head&shoulder done with the 85mm on a FF will not give the same effect (compression and overall bokeh) of a 50mm on a DX because the distance will be different and mainly because the 50 is a standard focal intended for standard "views" that on a cropped sensor brings things closer but the rest of the "effect" of the 85mm will be missed.

That said one must shoot with what he has at the moment. For example when you use a tele-zoom (like the 70-200) the difference will also be minimal.

Click to expand...

I agree with what you are saying, but the OP did say using any given lens, in which case the image will appear exactly the same.

hzmeyer said:

I know this has been discussed before, but is it really there? The actual subject size of the image falling on any sensor is the same for a given lens. You just get less coveage with a cropped sensor. The telephoto effect is achieved by enlarging the image. But why can't you just enlarge the image from a full frame sensor? My 5D Mark II, at 21 mega pixles, I would assume can be enlarged as much as a cropped sensor of lower total mega pixles to get the same "telephoto" effect.

Click to expand...

Absolutely correct. Apart from quality issues, you'll get the same pic if you crop the FF image.

If you are comparing your 21.1 MP 5D Mk II to an 8.2MP, then yes, you could just crop your 5D Mk II file and have the same amount of detail as the 20D image. This is becaus the pixels are packed together as densely on both cameras. However the 20D is a 6 years older than the 5D Mk II. If you compare current cropped sensors to current full frame sensors, the cropped sensors are pretty much always more dense. So if you were comparing a 7D to your 5D Mk II, if you cropped in the 5D shot, it would not have as much detail and either be a smaller image, or if you enlarged it to be the same size, it would be softer/less sharp. For a full frame to be able to crop to the level of a 7D it would have to be around 46 megapixels.

So if you are trying to shoot something off in the distance and the longest lens you have is a 300mm, the 7D will have the object fill more of the frame and have more detail than the 5D Mk II... so in that respect yes the telephoto factor is true. But if the crop camera has few than 1/2.56 (1/1.6^2) the number of pixels as the full frame, the full frame will get more detail.
--
~K

For a given lens focal length the use of a smaller than 35mm size sensor crops the area captured but does not change the image magnification. A 200mm lens on a Nikon APS-C camera may produce the same field of view as a 300mm lens on a full frame camera but it will still have the same approximately 4x image magnification of the 200mm lens when used on a full frame camera.

Slightly different question. 50mm lens on a crop camera = 80mm, what dof do you get at a given f stop, an 80mm lens or a 50mm lens????

Aperture and magnification determines depth of field. It does not matter if you change magnification by moving closer, changing focal length, cut your negative or sensor in half, look at a smaller screen or print it at a certain size. All sorts of other things changes at the same time though, most importantly perspective as perspective is determined by distance from subject to the light capturing part.

So the 50mm lens is 50mm regardless of camera. Dof stays the same. Field of view stays the same. Magnification stays the same. Perspective stays the same. Distance stays the same.

As soon as you start to change any of the parameters, the others changes as well. Except for the 50mm, they are always the same.
--
Anders

'It is nice to be important but it is more important to be nice'

Since your question used the word telephoto effect, then the answer is no. A telephoto lens is a specific lens design that creates magnification by bending and controlling the direction of light waves.

There is no magnification created by capturing a smaller area of the image projected by the lens. This is better described as a cropping effect. However, anytime you use the word crop, it is in relation to a larger size. Since almost every format has a format that is larger, they could all be labeled cropped sizes. So, this then makes the term rather silly.

This discussion really only comes into play with DX and FX systems where an FX lens can be used on both types of cameras. It is best to just accept each sensor size as being part of a camera system of a particular scaled-size for its intended purpose.

= tommy