Zeiss "Batis" AF lens line to be released for FF E-mount
Tariq Gibran wrote:
Lloyd may have this backwards (and I was incorrect earlier as well in stating the loss would be at the borders/ corners as I assumed barrel distortion). Typically, with barrel distortion, the center suffers less while the borders/ corners suffer more. The opposite occurs with pincushion distortion correction according to this:
\"Correction also redistributes an image\'s resolution; with pincushion removal, the edges will appear slightly sharper (at the expense of the center), whereas with barrel removal the center will instead appear slightly sharper (at the expense of the edges).\"
Firstly pincushion tends to be more common than barrel distortion with telephoto lenses, so I\'d be surprised if Lloyd was wrong on this. Secondly, I\'m afraid this is one of those cases where Cambridge in Colour is wrong on something - they aren\'t taking cropping and resizing into account.
With barrel distortion, the corners do gain from reduction in area, lose from the resampling process, and both the corners and the centre then lose from the fact the resulting image is too small and must be enlarged to match the original. So that makes for a net loss in both the corners and centre.
With pincushion distortion, the corners lose a lot from being stretched out, and from being resampled in general, but the centre is unaffected as there is no need to enlarge the resulting image, and the centre largely escapes any resampling.
If anyone is having difficulty visualising this, I\'ve made some images.
Image with barrel distortion:
Image with pincushion distortion:
Image with barrel distortion after correction:
Note that we are left with an image that contains gaps, areas that we can\'t reconstruct. These must be cropped out
and then the image must be resized back to the original dimensions. This affects image quality everywhere in the image.
Image with pincushion distortion after correction
In this case we have more image than we need so there is no need to crop and resize. Image quality is only compromised in the areas that were resampled, i.e. the corners, and importantly not in the centre.
Zeiss "Batis" AF lens line to be released for FF E-mount
Tariq Gibran wrote:
Lloyd may have this backwards (and I was incorrect earlier as well in stating the loss would be at the borders/ corners as I assumed barrel distortion). Typically, with barrel distortion, the center suffers less while the borders/ corners suffer more. The opposite occurs with pincushion distortion correction according to this:
\"Correction also redistributes an image\'s resolution; with pincushion removal, the edges will appear slightly sharper (at the expense of the center), whereas with barrel removal the center will instead appear slightly sharper (at the expense of the edges).\"
Firstly pincushion tends to be more common than barrel distortion with telephoto lenses, so I\'d be surprised if Lloyd was wrong on this. Secondly, I\'m afraid this is one of those cases where Cambridge in Colour is wrong on something - they aren\'t taking cropping and resizing into account.
With barrel distortion, the corners do gain from reduction in area, lose from the resampling process, and both the corners and the centre then lose from the fact the resulting image is too small and must be enlarged to match the original. So that makes for a net loss in both the corners and centre.
With pincushion distortion, the corners lose a lot from being stretched out, and from being resampled in general, but the centre is unaffected as there is no need to enlarge the resulting image, and the centre largely escapes any resampling.
If anyone is having difficulty visualising this, I\'ve made some images.
Image with barrel distortion:
Image with pincushion distortion:
Image with barrel distortion after correction:
Note that we are left with an image that contains gaps, areas that we can\'t reconstruct. These must be cropped out
and then the image must be resized back to the original dimensions. This affects image quality everywhere in the image.
Image with barrel distortion after correction
In this case we have more image than we need so there is no need to crop and resize. Image quality is only compromised in the areas that were resampled, i.e. the corners, and importantly not in the centre.
Zeiss "Batis" AF lens line to be released for FF E-mount
Tariq Gibran wrote:
Lloyd may have this backwards (and I was incorrect earlier as well in stating the loss would be at the borders/ corners as I assumed barrel distortion). Typically, with barrel distortion, the center suffers less while the borders/ corners suffer more. The opposite occurs with pincushion distortion correction according to this:
\"Correction also redistributes an image\'s resolution; with pincushion removal, the edges will appear slightly sharper (at the expense of the center), whereas with barrel removal the center will instead appear slightly sharper (at the expense of the edges).\"
Firstly pincushion tends to be more common than barrel distortion with telephoto lenses, so I\'d be surprised if Lloyd was wrong on this. Secondly, I\'m afraid this is one of those cases where Cambridge in Colour is wrong on something - they aren\'t taking cropping and resizing into account.
With barrel distortion, the corners do gain from reduction in area, lose from the resampling process, and both the corners and the centre then lose from the fact the resulting image is too small and must be enlarged to match the original. So that makes for a net loss in both the corners and centre.
With pincushion distortion, the corners lose a lot from being stretched out, and from being resampled in general, but the centre is unaffected as there is no need to enlarge the resulting image, and the centre largely escapes any resampling.
If anyone is having difficulty visualising this, I\'ve made some images.
image with barrel distortion:
image with pincushion distortion:
image with barrel distortion after correction:
Note that we are left with an image that contains gaps, areas that we can\'t reconstruct. These must be cropped out
and then the image must be resized back to the original dimensions. This affects image quality everywhere in the image.
image with barrel distortion after correction
In this case we have more image than we need so there is no need to crop and resize. Image quality is only compromised in the areas that were resampled, i.e. the corners, and importantly not in the centre.
Zeiss "Batis" AF lens line to be released for FF E-mount
Tariq Gibran wrote:
Lloyd may have this backwards (and I was incorrect earlier as well in stating the loss would be at the borders/ corners as I assumed barrel distortion). Typically, with barrel distortion, the center suffers less while the borders/ corners suffer more. The opposite occurs with pincushion distortion correction according to this:
\"Correction also redistributes an image\'s resolution; with pincushion removal, the edges will appear slightly sharper (at the expense of the center), whereas with barrel removal the center will instead appear slightly sharper (at the expense of the edges).\"
Pincushion tends to be more common than barrel distortion with telephoto lenses, so I\'d be surprised if Lloyd was wrong on this.
Secondly, I\'m afraid this is one of those cases where Cambridge in Colour is wrong on something - they aren\'t taking cropping and resizing into account.
With barrel distortion, the corners do gain from reduction in area, lose from the resampling process, and both the corners and the centre then lose from the fact the resulting image is too small and must be enlarged to match the original. So that makes for a net loss in both the corners and centre.
With pincushion distortion, the corners lose a lot from being stretched out, and from being resampled in general, but the centre is unaffected as there is no need to enlarge the resulting image, and the centre largely escapes any resampling.
If anyone is having difficulty visualising this, I\'ve made some images.
image with barrel distortion:
image with pincushion distortion:
image with barrel distortion after correction:
Note that we are left with an image that contains gaps, areas that we can\'t reconstruct. These must be cropped out
and then the image must be resized back to the original dimensions. This affects image quality everywhere in the image.
image with barrel distortion after correction
In this case we have more image than we need so there is no need to crop and resize. Image quality is only compromised in the areas that were resampled, i.e. the corners, and importantly not in the centre.
Re: Zeiss "Batis" AF lens line to be released for FF E-mount
Tariq Gibran wrote:
Lloyd may have this backwards (and I was incorrect earlier as well in stating the loss would be at the borders/ corners as I assumed barrel distortion). Typically, with barrel distortion, the center suffers less while the borders/ corners suffer more. The opposite occurs with pincushion distortion correction according to this:
\"Correction also redistributes an image\'s resolution; with pincushion removal, the edges will appear slightly sharper (at the expense of the center), whereas with barrel removal the center will instead appear slightly sharper (at the expense of the edges).\"
Pincushion is more common than barrel distortion with telephoto lenses. And this is one of those cases where Cambridge in Colour is wrong on something - it isn\'t taking image size loss / resampling into account.
With barrel distortion, the corners do gain from reduction in area, lose from the resampling process, and both the corners and the centre then lose from the fact the resulting image is too small and must be enlarged to match the original. So that makes for a net loss in both the corners and centre.
With pincushion distortion, the corners lose a lot from being stretched out, and from being resampled in general, but the centre is unaffected as there is no need to enlarge the resulting image, and the centre largely escapes any resampling.
If anyone is having difficulty visualising this, I\'ve made some images.
image with barrel distortion:
image with pincushion distortion:
image with barrel distortion after correction:
Note that the image is now too small, we will have to crop down to a smaller rectangle and then resize the whole thing.
image with barrel distortion after correction
All we need to do is crop back to the original dimensions, no resize necessary.
Apr 30, 2015 at 10:12 AM
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