20mm f1.7 FOV?

J

Jonathan12uiz

Well-known member
Is the Panny Pancake lens' field of view optimized for the 2x crop sensor? Meaning it will give me the same FOV as a 25mm full frame? or is the image circle on the pancake still full frame style?
 
There is no such thing as "being optimized for a sensor". A lens delivers the exact same field of view at all times. And the sensor will "see" as much of that view as it sees.

Any 20mm lens will deliver the exact same field of view as any other 20mm lens. The "crop factor" has to do with the notion that the smaller sensor will only "see" a smaller portion of what the lens is delivering.

As such, the 20/1.7 will deliver a field of view that's about the same as a 40mm lens on a "full frame" camera. If you took a 20mm "full frame" lens and put it on the GH1, it would give you the exact same field of view as the 20/1.7 on the GH1.
 
Barry_Green said:
There is no such thing as "being optimized for a sensor". A lens delivers the exact same field of view at all times. And the sensor will "see" as much of that view as it sees.

Any 20mm lens will deliver the exact same field of view as any other 20mm lens. The "crop factor" has to do with the notion that the smaller sensor will only "see" a smaller portion of what the lens is delivering.

As such, the 20/1.7 will deliver a field of view that's about the same as a 40mm lens on a "full frame" camera. If you took a 20mm "full frame" lens and put it on the GH1, it would give you the exact same field of view as the 20/1.7 on the GH1.
Click to expand...

I was kind of meaning it as in similar to the canon ef-s? lenses? where the 25mm if forced on a full frame camera it would only have a small circular picture in the middle of black. because the lense was designed to give a 25mm Full frame FOV on a crop sensor.

Where as YES a 25mm Full frame lens will be 25mm on any camera it is mounted to, but we have a 2x crop so it would = a 40mm on our camera, BUT I was wondering if the 20mm was optimized for our crop sensor. so that it would equal what a full frame camera sees @ 20mm?

Did that make sense?
 
Again, it doesn't work that way.

The EF-S lens is the same mm as the EF lens. If you take a 50mm EF-S lens, and a 50mm EOS lens, and put them both on the 7D, you'll get exactly the same image. If you put them both on the 5D, you'll get exactly the same image, except that the EF-S lens will vignette on the bigger sensor. But the image within that frame, within that circle, will be exactly the same on both.

The only "optimizing for a sensor" that gets done, is that on the smaller sensors, they design the lens less expensively because it doesn't have to cover such a large frame. But the perspective, field of view, and DOF characteristics are all the same.

The lens doesn't change, it's the size of the sensor that makes the difference. There is no such thing as optimizing a lens so that a 20mm on a 2x crop = a 20mm on a 1.6x crop or anything like that. It doesn't work that way.

If you want to look strictly at field of view, and ignore all other aspects of imaging, then it is always the case that equivalent field of view is achieved by multiplying focal length by crop factor. So if you want the fov that a 20mm lens delivers on a 1.0 crop, when mounted to a 2.0 sensor, you'd have to use a 10mm.
 
The EF-S lenses are designed to throw a circle around an APS-C sensor. When placed on a full framed sensor it vignettes (puts a border without light.)

The GH-1 and AF100 are micro 4/3, a tad smaller than the APS-C sensor. The m4/3 is fully covered with the circle light the 20mm throws. It won't vignette. The DOF will be that of any 20mm lens and the field of view will be that of the m4/3 sensor according to the crop factor. (Which you noticed on the m4/3 sensor is 2x, or approximately 40mm FoV.

Edit: Barry beat me to it. LOL
 
Barry_Green said:
Again, it doesn't work that way.

The EF-S lens is the same mm as the EF lens. If you take a 50mm EF-S lens, and a 50mm EOS lens, and put them both on the 7D, you'll get exactly the same image. If you put them both on the 5D, you'll get exactly the same image, except that the EF-S lens will vignette on the bigger sensor. But the image within that frame, within that circle, will be exactly the same on both.

The only "optimizing for a sensor" that gets done, is that on the smaller sensors, they design the lens less expensively because it doesn't have to cover such a large frame. But the perspective, field of view, and DOF characteristics are all the same.

The lens doesn't change, it's the size of the sensor that makes the difference. There is no such thing as optimizing a lens so that a 20mm on a 2x crop = a 20mm on a 1.6x crop or anything like that. It doesn't work that way.

If you want to look strictly at field of view, and ignore all other aspects of imaging, then it is always the case that equivalent field of view is achieved by multiplying focal length by crop factor. So if you want the fov that a 20mm lens delivers on a 1.0 crop, when mounted to a 2.0 sensor, you'd have to use a 10mm.
Click to expand...

ok thats what I thought originally, an article I read recently worded things a little differently so I wanted to ask.
 
Yes... 20mm lens is 20mm lens regardless of system's cropping factor. FOV of the lens depends on the system's cropping factor. Sensor cropping, zoom cropping, 1:1 cropping, etc. It's just a matter of vignetting for using lenses that can't cover entire sensor area.
 
Basically, a lens "optimized" for a crop sensor uses LESS GLASS then a full frame lens. Cropped sensors and lenses are like babies and cookies: It saves money to bake a smaller cookie since a baby can't eat a giant (full frame) cookie. But if you compared small 20mm cookies and large 20mm cookies, they'd have the same curvature, just a smaller diameter.

Try the Tamron Focal Length Comparison tool. Set a full frame lens at 40mm = 56.5 degrees FOV (diagonal) vs 20mm = 94.1 degrees FOV.
 
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