zoom vs crop

<p>Right now my longest lens is my 80-200 2.8 (push pull). I have found that even though it is old it still takes great pictures and when i reach the end of it's zoom capibilities I am able to crop my photos and get very good shots from longer distances. My question is more of a theoretical one where I wondered if there would be any (noticable) difference between an image that was say taken at 200mm then cropped vs. one that was shot at say 300mm. With all variables being the same like f-stop and shutter speed I would tend to believe they would be very close indeed. I am by no means an expert photographer so I am posting this theory question in hopes that perhaps the more knowledgeable photographers may be able to explain it to me.</p>

<p>Yes there may be a difference (depending on how you view the final images) if you took the two shots from the same spot and enlarged the one taken at 200mm to the same size as the one taken at 300mm. If you are using film, there will be more grain visible in the one taken at 200mm; and if you're using digital, instead of grain, there may be pixellation in the one taken at 200mm. OTOH, if you zoomed with your feet (ie moved closer with the 200mm shot) so that the image taken with the 200mm shot was the same size as the image taken further back with your 300 mm lens, there should be no discernable difference between the shots.</p>

<p>I agree. My 18-200 mm zoom already acts like a 27-300 mm on a D300. The output size is nearly 14" on the long side. Since I only need 10", when I finish cropping the 18-200 is now more like a 400 mm on the long end! Plus, I have the advantage of tilting and precisely cropping the final photo the way I want it.</p>

<p>Shooting with a longer lens would utilize all of the sensor area, and therefore all of the resolution, of the sensor (or film). Cropping and enlarging to the same print size as the longer lens would drop out the resolution of the area that was cropped off. Assuming the same level of optical quality in both lenses and the same print size, the cropped image would look inferior - you'd be lowering the camera's resolution (in megapixels) <em>and</em> the lens' resolution (lines of resolution) by 1/3.</p>

<p>In addition to what has been said, the short answer is no, the images will not be the same. The longer the lens, the more the background is compressed and the more OoF the background becomes. In other words, if you frame a shot with a 200mm lens and then back up to frame the same shot with a 300mm lens, you will have less background with the 300mm lens and the background will be more OoF, all else being equal. If, therefore, you frame a shot with the 200mm lens and then crop it, you still won't have compressed the background as you would have had you shot with a 300mm lens. In other words, there is a difference. </p>

<p><em>If, therefore, you frame a shot with the 200mm lens and then crop it, you still won't have compressed the background as you would have had you shot with a 300mm lens...</em></p>

<p>If the ultimate framing is the same, it doesn't matter whether you use a 300 mm lens or shoot with a longer lens and crop the results. Either way, you will be the same distance from the subject and have the same perspective, hence depth compression. You will, however, have a greater depth of field at the same f/stop and, of course, less resolution (because you are throwing pixels or film away by cropping).</p>

<p>No, it won't! A longer lens compresses the background. In the shots below, the top shot as @ 300mm and the bottom @ 200mm. I have "less" background with the longer lens. </p>

<p> </p><div></div>

<p>It really depends on what your subject is, how far the main subject is from you and how far the background is from the main subject. If you were shooting a static object, for example, using the above shot, if the subject was standing directly in front of the lighthouse, you really would not see much of a difference.</p>

<p>Perspective depends ONLY on distance, including the relative size of objects in the foreground and background. These examples were taken from different distances so that the person was the same size in the viewfinder.</p>

<p>If you stand in the same place, shoot with both lenses and crop the 200mm shot to the same FOV as the 300mm, the same background "compression" will occur (but the DOF will be greater in the 200mm shot).</p>

<p>Yes, Edward and Elliot nailed it.<br>

It would be also benefitial to see the pictures taken from standing in the same location, and providing crop to the same size of the person.</p>

<p>Dear all,</p>

<p>Perspective depends on the distance to the subject as well as the true focal length of the lens. Remember the formula (1/v -1/u = 1/f), where f is the focal length, u the object distance and v the image distance. What this does for a tele lens is it magnifies the distant objects more compared to the nearer objects. The more tele you have the more the distant object is magnified compared to the nearer object. Say you have a statue in the background of your loved one you are shooting at with a lens having focal length of 50 mm, and the statue looks too small compared to your subject. What then you do is you pick up a different lens with say 100mm focal length and look through the view finder. Your subject is magnified, but the statue is magnified more, so now the proportion looks ok. This is what photographers use every day.</p>

<p>So the bottom line is, it is different shooting with a larger lens and doing the crop work. There are other things like loss of detail (read pixels) and decrease of depth of field while using a crop alternative, but those are discussed already.</p>

<p>Cheers.<br>

Prasun.</p>

<p>No, perspective depends ONLY on point of view. It does not depend on the focal length of the lens. The reason why you switch to a 100mm to get the background bigger, is because a 100mm lens allows you to stand further, at the same time frame the foreground same as before. The effect of this action moved everything further from your point of view. Since object size on image plane is directly proportional to the distance, it has the effect of shrinking foreground object more than shrinking the background object.<br /> Take a numeric example, using 50mm: person = 1m, statue = 1000m, using 100mm: person = 2m, statue = 1001m. The person shrink to 1/2 = 0.5 times as big, the statue shrink to 1000/1001 ~ 1 times as big. Because 100mm lens has about 2 times magnification, the result is the status seems twice as big.<br /> So, perspective alone controls compression, focal length controls depth of field. Focal length and Crop factor together control FOV<br>

200mm crop to 300mm = 300mm FOV and compression + 200mm Depth of Field.</p>

<p>I think I made a mistake above: 200mm Crop to 300mm, as long as the aperture does not change, will offer 300mm depth of field. It has something to do with the concept of "Circle of confusion"<br>

I know the DOF part is a bit brain twisting but here is a good read: <a href="http://www.film-and-video.com/dofmyth.htm">http://www.film-and-video.com/dofmyth.htm</a></p>