isoterica
Established
The focal length of the lens whether it is on a full frame or smaller sensor camera remains the same. So 50mm is still 50mm. 100mm is still 100mm.
The field of view or area that lies within the borders of the photo frame is effected by a small sensor 'cropping' it, as if you cut a section out of the middle of a full frame photo. If you have a 1.6 crop, then 1.6x is the difference between a full frame field of view and a crop sensor field of view.
If one photographer has a full frame camera and the other a crop sensor camera and they stand side by side taking a photo, a full body shot of a man for the full frame photographer would look different for the crop sensor photographer who might just see the man's head and shoulders. If you are not comparing one camera to the other camera it shouldn't make a difference, you will stand where you need to in order to create the proper composition or in this case get the entire person in frame. The viewfinder or liveview on your lcd gives you an accurate enough perspective of what will be in frame. There should be no surprises.
There are benefits to crop sensors, such as in macro photography when it is one's intent to get closer. You can do so without physically changing the size of the image via software cropping, where as if you were full framed you might want or need to crop to enhance, say, the center of a flower making it appear larger. Crop sensors might not be as favorable in sports photography or journalism and yet, you learn to work with what you have to get the shot you want in frame.
Regarding lenses, if a fish-eye lens designed for a full frame camera is put on a full frame camera the result is 'intentional' barrel distortion. You know the classic rounded panorama shot-- though some fish-eye lenses are less distorted. However if the same lens is put on a crop sensor camera the distortion isn't as emphasized. Again this is due to the crop. Your camera will be cropping out the outer edge of the photo frame that is most distorted by the fish-eye lens. Some mfg's make special crop sensor fish-eyes for this reason. Crop sensors do not add distortion to lenses so even if you have a lesser quality lens with some distortion on the edges, the crop sensor camera will take from the center where the image is more sharp and without distortion.
Every once in a while there is a photographer/blogger or writer, that shares this info and it is clear but most of the time you hear.. "Oh that 50mm is like 80 mm on a crop body." It's basically a lazy way of stating something that would be better explained in full, which would take only a few more words really. But it is what it is.
Depth of Field.. =D
The field of view or area that lies within the borders of the photo frame is effected by a small sensor 'cropping' it, as if you cut a section out of the middle of a full frame photo. If you have a 1.6 crop, then 1.6x is the difference between a full frame field of view and a crop sensor field of view.
If one photographer has a full frame camera and the other a crop sensor camera and they stand side by side taking a photo, a full body shot of a man for the full frame photographer would look different for the crop sensor photographer who might just see the man's head and shoulders. If you are not comparing one camera to the other camera it shouldn't make a difference, you will stand where you need to in order to create the proper composition or in this case get the entire person in frame. The viewfinder or liveview on your lcd gives you an accurate enough perspective of what will be in frame. There should be no surprises.
There are benefits to crop sensors, such as in macro photography when it is one's intent to get closer. You can do so without physically changing the size of the image via software cropping, where as if you were full framed you might want or need to crop to enhance, say, the center of a flower making it appear larger. Crop sensors might not be as favorable in sports photography or journalism and yet, you learn to work with what you have to get the shot you want in frame.
Regarding lenses, if a fish-eye lens designed for a full frame camera is put on a full frame camera the result is 'intentional' barrel distortion. You know the classic rounded panorama shot-- though some fish-eye lenses are less distorted. However if the same lens is put on a crop sensor camera the distortion isn't as emphasized. Again this is due to the crop. Your camera will be cropping out the outer edge of the photo frame that is most distorted by the fish-eye lens. Some mfg's make special crop sensor fish-eyes for this reason. Crop sensors do not add distortion to lenses so even if you have a lesser quality lens with some distortion on the edges, the crop sensor camera will take from the center where the image is more sharp and without distortion.
Every once in a while there is a photographer/blogger or writer, that shares this info and it is clear but most of the time you hear.. "Oh that 50mm is like 80 mm on a crop body." It's basically a lazy way of stating something that would be better explained in full, which would take only a few more words really. But it is what it is.
Depth of Field.. =D
zuiko85
Veteran
Come to think of it I've got a couple of Kodak Tourist cameras and the Kodak multi-format kit. Without a mask the camera is a 6X9 or, I can put in the 6X6 mask or the 6X4.5 mask. Ta Da, a "crop sensor" film camera.
isoterica
Established
sevo
Fokutorendaburando
As a matter of fact, crop sensors are an advantage for tele-centric subject matter as they extend every lens by factor 1.5. Canon are still producing a dedicated pro crop body, as their sports photography customers request it.
Spleenrippa
Yes, Right There
A picture is worth a thousand words 
*pic taken from Wikipedia
*pic taken from Wikipedia
clayne
shoot film or die
It's not just about cropping and how that affects composition. DOF is inherently different if you shift the distance to "match" the equivalent angle of view.
isoterica
Established
You are right in the telephoto department, I was thinking more of shooting an entire baseball field wide angle in which case it wouldn't be so wide. Either way, crop sensor camera's can have an advantage as far as getting in closer.
Dwig
Well-known
Your confusion comes from thinking that focal length, in and of itself, has an impact on the perspective rendered (foreshortening, ...). This is totally false.
The only thing that affects perspective is relative distances from the camera to the subject, the foreground object(s), and the background. In your portrait example, the only thing affecting the perspective is the camera to subject distance. The format (sensor/film size) and the lens focal length have no impact.
The only effect of focal length is the field of view on a given format. If you shoot a portrait from, say, 8 feet (subject to lens distance) it doesn't matter if you use a 50mm lens on 4/3 (2x crop factor) or FF. If you crop both to the same field of view the perspective will be identical. In fact you could use a 12mm lens on either camera shooting from the same 8ft distance and cropping to a matching field of view will yield exactly the same perspective.
clayne
shoot film or die
Yes, but what you're describing is really cropping of the FF-side to match the already cropped crop-sensor output. At the same distance this would yield the same perspective - but in no way would it be natively 50mm. And even if one tries to play mathematical games to emulate the same perspective as 50mm, uncropped, they will not get around the change in DOF.
Merkin
For the Weekend
I'm not concerned about DOF. If anything, greater depth of field is good for the way I shoot. I only wanted to make sure that I could get flattering portraits.
clayne
shoot film or die
Define "the way you shoot." I could understand you if you were talking something like street photography, but traditionally greater DOF doesn't necessarily go hand in hand with flattering portraits.
Merkin
For the Weekend
I don't like razor thin DOF in my portraits. I shoot most of my portraits at f4 or 5.6. I don't shoot in a studio, so I like a little context.
Dwig
Well-known
To think that there is some concept as being "natively 50mm" is rather nonsensical. Obviously you are narrowly considering 35mm FF some magic format and all others second-class entities.
My discussion targeted the OP's questions about perspective. DOF is a horse of a different color. With lenses yielding matching fields of view and when shooting the same scene from the same position there will always be more DOF at any one f/stop the smaller the format. 4x5 yields more DOF than 8x10, 6x7 yields more than 4x5, 35mmFF has more than 6x7, ... . This is nothing new that's been brought on by the so called "crop sensor" digital formats. It's been a fact of life in the photo world since the development of photography.
sevo
Fokutorendaburando
There is no such thing as a "native" focal length.
The difference in DOF merely is a difference in aperture - stop down in proportion to the format increase, and there is no difference. This also implies that smaller format lenses with the same DOF and angle of view will be proportionally faster.
If any, the real difference is diffraction in relation to DOF - with growing film/sensor size, the margin for enlargement at a aperture delivering identical DOF decreases. Past some point rather smaller than 4x5" we are already inherently diffraction limited - people requiring large prints can only benefit from increasingly larger film/sensor formats if DOF is no or a manageable issue (subjects near infinity as well as those where the focal plane can be appropriately placed with camera movements) or low DOF is desired/acceptable.
clayne
shoot film or die
Cmon guys, subject distance. This entire conversation is revolving around keeping the same perspective as a "full-frame" shot vs cropped. You cannot have the same perspective with the same DOF, using the same lens on a body that crops vs one that doesn't. One simply has to move to keep the same perspective (from the point of the cropped sensor, not the full frame) and with that, DOF changes as a factor of focal distance. Inherently the crop sensor will have greater DOF for the same perspective as a FF shot with the same lens because the crop sensor version of the shot would have required moving away from the subject.
Dwig
Well-known
Very, very wrong!
If you move you change perspective, period, whether you change formats, change lenses, neither, or both.
clayne
shoot film or die
You are absolutely correct on that and bad choice of wording on my part. What I really meant was "framing" but that of course does not take into account the actual change of perspective or angle of view as a result.
But beyond all that basically the only possible thing that can ever be equaled is cropping the FF shot to the same as the cropped sensor shot. No combination of vectors can be entirely controlled to equal the same results be that AOV, DOF, whatever.
Crop sensors are a great way to handicap good lenses.
But beyond all that basically the only possible thing that can ever be equaled is cropping the FF shot to the same as the cropped sensor shot. No combination of vectors can be entirely controlled to equal the same results be that AOV, DOF, whatever.
Crop sensors are a great way to handicap good lenses.
Dwig
Well-known
True only to a degree and not at all unless you replace "good lenses" with "good lenses designed for some larger format".
Even FF/FX sensors handicap good lenses when those lenses are designed for larger format (e.g. Hasselblad H series lenses, Leica S series lenses, ...)