Identical pictures w/ 50mm lens on a crop sensor body & FF body

[ken_mckenna]

<p>Is it possible for me, with a 50mm lens on a crop sensor body, to get identical perspective and framing (field of view) as a 50mm lens on a full frame body? As I understand it perspective is controlled by distance, and to get the same framing as a 50mm on a FF body, I would have to move my camera position backwards - thus changing the perspective. <br>

Basically I want to get the <strong>exact</strong> same shot with a 50mm lens on a crop body as I would on a full frame body. Is this possible?</p>

[Matt Laur]

<p>No, for exactly the reasons you just described.<br /><br />That is, unless you're willing to crop the image from the FX body. Otherwise, you want a 30mm-ish lens on the DX, or an 85mm-ish lens on the FX to make things fair. </p>

[ken_mckenna]

<p>But isn't the image zoomed in with my FX body? Wouldn't cropping it make it even smaller? </p>

[Matt Laur]

<p>No, the FX body has a larger sensor. If you stand in the same place, and use the same lens (presuming it's one that will work on an FX body), the image recorded by the FX body will contain the exact same image as the DX body PLUS MORE image beyond that.</p>

[ken_mckenna]

<p>Ok I think I'm confused because I misinterpreted FX to mean crop sensor. I am using the canon lens set. So 50mm on a crop sensor doesn't mean the image is zoomed in? I guess with how you're speaking, I have a DX body.<br>

edit: the image <em>must </em>be zoomed because with my 50mm lens on my crop body (20d) it seems as though I have a narrow (i.e. cropped) field of vision</p>

[devon_mccarroll]

FX is full frame, DX is crop sensor. So a 50mm lens on an FX body is just like it would have been on a film camera,

showing the full view. On a DX (crop sensor) body, the ratio is usually around 1.6 because of the smaller sensor size, so

it's essentially cropping the image, making it appear closer. So if you put that 50mm on a DX body, it would show a field

of view that would look like the equivalent of around 80mm on an FX body. It's not zoomed, it's just cropped because of the smaller sensor.

[Andrew Garrard]

Wow, cross system terminology confusion. :-)

 

DX and FX are Nikon terms for their 1.5x crop (~24mm x 16mm) and full-frame (~36mm x 24mm) sensor systems respectively. Canon have

full frame that's the same as Nikon's and crop sensors that are slightly smaller (1.6x, ~22.5mm x 15mm) - they have a few 1.3x crop

discontinued models, too. Nikon use DX in lenses to indicate much the same as Canon do with EF-S, although EF-S lenses physically won't fit

on a full-frame Canon, while DX lenses will mount on a full frame Nikon (but generally produce poor borders). Nikon came up with the FX

branding to distinguish their full-frame cameras from their historical ones as of the D3, and started using DX to refer to crop cameras at that

point. Canon had full frame much longer (original 1Ds), and never branded the distinction. "Full frame" and "crop" are more platform-agnostic

terminology, though a lot of medium format digital shooters may object.

 

Terminology aside, the advice is sound.

[Alan Marcus]

<p>About perspective:<br>

If you stand before a window and trace with wax pencil the outline of objects seen, this drawing depicts the "human perspective". Such a drawing presents an accurate geometrical representation, as seen by the human eye.</p>

<p>To duplicate the perspective as seen in the drawing, a camera must be positioned exactly at the spot previously occupied by the eye. We expose and make a contact print (print the exact same size as the image playing on film or chip inside the camera). We now observe this contact print from a distance exactly equal to the focal length of the camera lens. Follow these instructions and the observer will see a picture that has the same perspective as the wax pencil drawing. This is a difficult task for today's miniature cameras, but it can be accomplished if we view the contact print using a magnifying glass. This is the case when viewing 35mm slides with a hand-held viewer. If we view from normal reading distance the perspective will not be correct.<br>

How about making an enlargement, say 8x10, from this slide or negative. To accomplish we must magnify the original camera image eight times (8X). To obtain the same perspective as the wax pencil drawing, the viewing distance is now the focal length times 8 = 400mm = 15 inches = normal reading distance. This is the stuff of perspective.<br>

We try the same feat using a compact digital. The full frame 35mm produced an image 24mm by 36mm. The compact digital produces an image 16mm by 24mm. The difference is 36 ÷ 24 = 1.5 for length and 24 ÷ 16 = 1.5 from height. In other words, the full frame is 1.5 times larger. This is the so-called magnification factor.</p>

<p>If we know the magnification factor is 1.5, we now know that to make an 8x10 we need 1.5X more magnification. So to make the 8x10 the enlarger must magnify 8 x 1.5 = 12X (thus smaller camera needs more magnification to 12X vs. 8X to make the 8x10.) The smaller camera needs a shorter lens to duplicate the perspective of the full frame. We mounted a 50mm on the full frame. We mount a 50 ÷ 1.5 = 33mm on the compact digital (most round to 30mm). The viewing distance print-to- observer is focal length times magnification 30 X 12 = 360mm = 14 inches = normal reading distance.</p>

<p>Conclusion, a 30mm on a compact digital delivers the same perspective as a 50mm on a full frame.</p>

<p>More and more gobbledygook from Alan Marcus </p>

[francisco_disilvestro]

<blockquote>

<p>Basically I want to get the <strong>exact</strong> same shot with a 50mm lens on a crop body as I would on a full frame body. Is this possible?</p>

</blockquote>

<p><br />For static subjects, you could take two or more images with the crop body and then stitch the images digitally. <br /> You need more than two captures due to the necessary overlap required by stitching / panorama software.</p>

[Alan Marcus]

<p>You mount a 50mm on a compact digital. You specify the final image size and viewing distance. Assume an 8x10 print made using the compact digital. The magnification needed is 12X. The viewing distance is 50mm X 12 = 600mm = 23 ½ inches.</p>

<p>To duplicate on a full frame, the magnification will now be 8X. The math is what focal length times 8 = 600 (the viewing distance). The answer is 75mm. In other words, a 75mm on a full frame delivers the same perspective as a 50mm on a compact.<br>

Again the magnification factor of 1.5 is the key.<br>

50 X 1.5 = 75mm (focal length needed) on the full frame.<br>

Viewing distance is 75 X 8 = 600mm = 23 ½ inches.<br>

The viewing distance of the two finished images must be identical to deliver the same perspective. The viewing distance is the focal length of the taking lens times the magnification to make the finished print.<br>

More and more and more nonsense from Alan Marcus</p>

[colin carron]

<p>Here is an image showing a full frame shot with, marked inside it, the image which would be registered if the lens were used ona 1.6 crop camera. As you can see the image is the same inside the crop sensor line but the full frame sees a wider view. Same lens though.</p>

[colin carron]

<p>...and here's the image....</p><div></div>

[JDMvW]

<p>As Matt and others have indicated, perspective is the same for all lenses from the same location, although the amount of the scene included will differ with each focal length. If you move, you cannot keep the same perspective.<br /> As the wonderful, old <em>Life Library of Photography* </em>volume, <em>The Camera,</em> put it</p>

<blockquote>

<p>As long as you do not move your camera,<br />changes in focal length have little<br />apparent effect on perspective, ... But if<br />you move the camera and change focal<br />length, perspective alters dramatically.<br />Sizes and distances of objects are distorted,<br />producing effects that are sometimes<br />useful, sometimes a nuisance.</p>

</blockquote>

<p>_________<br /> *These are common and each volume can be bought for a few dollars on-line. Get the first edition printed in gravure. The illustrations of B&W work are like seeing the original print.</p>

[jcuknz]

<p>You can get the same sized image with the lens on either body but they will not be identitical because the perspective changes as you change from camera to camera. You moving further away with the APS body than with the FF body.</p>

[William Michael]

<blockquote>

<p>Basically I want to get the <strong>exact</strong> same shot with a 50mm lens on a crop body as I would on a full frame body. Is this possible?</p>

</blockquote>

<p>It is really a ‘theory’ question and the absolute answer is: No.</p>

<p>As previously mentioned change the shooting distance and that changes the PERSPECTIVE</p>

<p>Not even with stitching, can the two shots be the ‘exact same shot’, as the DoF will be different between shots, in consideration of the different FORMAT SIZES of the cameras used in the comparison.<br>

If the DoF were to be made the same in each shot, by varying the aperture; then the Shutter speed or ISO must also be changed and that will mean different noise/grain (for Static Subjects) and or movement which will be captured, differently.<br>

In the absolutely rare case that: the Subject were static; the camera securely tripod mounted; the aperture changed between shots to accommodate the exact same DoF and then ONLY the Shutter Speed changed to allow for the exact same exposure – the BOKEH would be different.</p>

<p>But as mentioned, the question is theoretical: a more practical real world answer in consideration of <a href="/beginner-photography-questions-forum/00bGp6">your subsequent post regarding the Genre of Photography in which you are engaged</a> (street photography), it is better that you are seeking an additional lens, or digital camera, or both. </p>

<p>WW</p>

<p> </p>

[grh]

<p>There's a lot of geometry that goes into an image: sensor size, focal length, position of the camera with respect to the subject, other elements of the image like background. Changing even one of those elements means the image will be different. Thus, modifying just the sensor size is enough to make the answer "no".</p>