Please stop promoting crop sensors for the "extra reach"

[Nettles]

To much maths. Just get the lens that fits fits framing the way you want it. It doesn't matter the numbers on the lens focal length if it gets the image you want

Well, in a way it does. Years ago I remember seeing a shot in a forum of a wine bottle taken with a 50mm lens fitted to a Canon 1.6x crop sensor camera. You could see the optical distortion caused by the 50mm lens' angle-of-view. The lens was being used as an 80mm (50x1.6).

A true 80mm wouldn't have distorted the subject, which is why this focal length is a good starting point for closer portraits.

 

[qleak]

Well, a way it does. Years ago I remember seeing a shot on a forum of a wine bottle taken with a 50mm lens fitted to a Canon 1.6x crop sensor camera. You could see the optical distortion caused by the 50mm lens' angle-of-view. The lens was being used as an 80mm (50x1.6).

A true 80mm wouldn't have distorted the subject, which is why this focal length is a good starting point for closer portraits.

Perspective distortion only depends on the field of view (assume viewing distance of a print is fixed otherwise we end up with some interesting "chuck close" effects).

An equivalent pair of lenses. For example:

70mm on APS-C (1.5 FLM) and
105mm on FF

will produce the same perspective distortion when at the same distance from the subject because they have the same field of view.

 

[480sparky]

Perspective distortion has zip to do with sensor size and focal length of any lens you're using.

The distortion is strictly a function of your position relative to the subject. The only way to alter perspective distortion is to move the camera or the subject.

 

[Braineack]

Well, in a way it does. Years ago I remember seeing a shot in a forum of a wine bottle taken with a 50mm lens fitted to a Canon 1.6x crop sensor camera. You could see the optical distortion caused by the 50mm lens' angle-of-view. The lens was being used as an 80mm (50x1.6).

A true 80mm wouldn't have distorted the subject, which is why this focal length is a good starting point for closer portraits.

the 80mm shot at the same distance, using a FF sensor would look the same. It's all about the distance to subject.

 

[Ysarex]

Ysarex - from what I recall in macro talks the difference between your average 1.6/5 crop and fullframe in depth of field is about one stops worth of aperture. Fullframe bodies can oft also close down one more stop of aperture before diffraction takes effect as strongly - plus they tend to (these days) have a wider useable ISO range.

So in theory you can up the ISO - close down the aperture and get a similar depth of field on fullframe.

You can do that and in some specific cases that would be the end result. I'm just concerned that the principle is correctly understood. DOF increases in practice with shrinking recording media. Circle of confusion increases as recording media increases.

Zack Arias has it about right in that video when he stresses that the difference between APS and FF today is pretty insignificant.

And there are so many other variables: For instance consider that there's more than one way to look at ISO useability. At base ISO my Fuji X-E2 (APS) has almost a stop more usable dynamic range than a Canon 6D and even though the Canon 6D may have equivalent or even better noise performance at ISO 400 to my Fuji at ISO 200 it then has even less dynamic range dropping to about 1 & 1/3 stops less dynamic range than my X-E2.

Diffraction limits are worth mentioning though for sure. That's one of the differences that matters between these various cameras. I start running into diffraction limits with my compact before I hit f/8. On the old 8x10 with a 360mm lens I never thought twice about cranking it down to f/64. Of course that still gave me less DOF than I get from the compact at f/5.6

Joe

 

[Designer]

I just don't understand how Medium is bigger than Full.

There's large format (i.e.; 8x10 and larger), then there is medium format (4x5, 120, etc.), and back in days long gone, the 35mm cameras were all called "miniature" (i.e.; small format).

Somehow the large and medium formats remained what they were originally named, but the 35mm format became the "standard", at least with those photographers who no longer carried around something larger.

 

[snowbear]

Not an exact comparison but:
My D40 is smaller and lighter than my gripped N90s, so I can hold the D40 at arm's length much easier than I can with the "full frame" film body. Yes, in this case, DX has more reach than FX/35mm Film.

 

[Nettles]

the 80mm shot at the same distance, using a FF sensor would look the same. It's all about the distance to subject.

If I understand you correctly, that's incorrect because of the restraints of the design and optical characteristics of each lens. The distance-to-subject with the 50mm causes an inevitable distortion you wouldn't get with the 80mm when the subject is similarly framed. The 80mm will always flatten perspective.

 

[Scatterbrained]

the 80mm shot at the same distance, using a FF sensor would look the same. It's all about the distance to subject.

If I understand you correctly, that's incorrect because of the restraints of the design and optical characteristics of each lens. The distance-to-subject with the 50mm causes an inevitable distortion you wouldn't get with the 80mm when the subject is similarly framed. The 80mm will always flatten perspective.

Incorrect. Distortion (on a rectilinear lens) is an effect of perspective. Take that 50mm lens, back up a bit (or simply level it) and then take another shot. Suddenly the distortion is gone. The reason why 85mm tends to "flatten" the subject is because it forces you to get further away. There is a difference between lens distortion, be it mustache, barrel, pin cushion etc, and perspective distortion.

 

[Nettles]

Thanks. Perhaps a key phrase in my point is "when the subject is similarly framed".

 

[bribrius]

the 80mm shot at the same distance, using a FF sensor would look the same. It's all about the distance to subject.

If I understand you correctly, that's incorrect because of the restraints of the design and optical characteristics of each lens. The distance-to-subject with the 50mm causes an inevitable distortion you wouldn't get with the 80mm when the subject is similarly framed. The 80mm will always flatten perspective.

Incorrect. Distortion (on a rectilinear lens) is an effect of perspective. Take that 50mm lens, back up a bit (or simply level it) and then take another shot. Suddenly the distortion is gone. The reason why 85mm tends to "flatten" the subject is because it forces you to get further away. There is a difference between lens distortion, be it mustache, barrel, pin cushion etc, and perspective distortion.

that sounded really informative unfortunately I didn't even remotely grasp it. I had no idea there were so many types of distortion it sounds complicated. If I post process and click on the distortion box does It fix all that? People have often told me my photos have distortion. I don't see it no idea wtf they are talking about.

 

[qleak]

that sounded really informative unfortunately I didn't even remotely grasp it. I had no idea there were so many types of distortion it sounds complicated. If I post process and click on the distortion box does It fix all that? People have often told me my photos have distortion. I don't see it no idea wtf they are talking about.

It's really quite simple there's just one type of distortion (perspective distortion). Narrower fields of view produce compressed (flattened) perspective and wider field of view produce more 3 dimensional images.

You can change the field of view by cropping, so if the subject is identically framed, it's all about the distance from the subject

closer -> thinner and more 3d
farther -> wider and more 2d

We're particularly sensitive to minute changes to a human face so I suggest you look at this with respect to portraits. This is a good starting point.

Keep in mind the above link is for a FF camera, if you're shooting with your D7100 you'll have to multiply the focal length on your camera by 1.5 (and be at the same distance to the subject) to get the same effects.

 

[Braineack]

the 80mm shot at the same distance, using a FF sensor would look the same. It's all about the distance to subject.

If I understand you correctly, that's incorrect because of the restraints of the design and optical characteristics of each lens. The distance-to-subject with the 50mm causes an inevitable distortion you wouldn't get with the 80mm when the subject is similarly framed. The 80mm will always flatten perspective.

if you were shooting a 50mm on your Rebel and at 80mm on a 5D standing from the same location, shooting the same subject--the perspective distortion would be the same. Because the perspective would be the same.

if you were shooting a 50mm on your Rebel and then zoomed to 80mm and stood from a further distance to framed the same shot--the perspective distortion would not be as severe. Because the perspective would not be the same.

 

[astroNikon]

If a truck is driving down the middle of the street at you doing 50mph
and you are standing in the middle of the street with a d610 and a d7100 both on tripods and sync'd remote releases.
and you have the same 85mm/1.4G lens on both of them
and if you take photos of the truck as it approaches you at speed
and if the truck driver doesn't notice you in the middle of the street.
in the end, it doesn't really matter.

now if someone found the memory cards in the ditch and started comparing the photos
they'll see the truck's grill in much more fine detail with the DX than the FX.
with with the FX, they'll be able to see more of the trucks grill

the main issue is hopefully one shot got the license plate

 

[Tailgunner]

Except that an 18 MP crop sensor will out-resolve a similar crop from a full frame camera.

The only way this isn't true is if your full frame camera has a crazy amount of MP, like with the Phase Ones and D800, and even then, you'll have more noise from the FF crop.

So is this an example of using the wrong tool for the job? Is the DX mode on a FF body there just to help one save on storage space?