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07-29-2015, 09:23 AM   #1
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wanted: DA 15 perspective distortion examples

I was lightly looking into a DA 15 and wanted to see photos that empathize prospective distortion. I have a Sigma 10-20 and love the PD it gives but wanted to compare examples

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Randy

07-29-2015, 09:32 AM   #2
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This thread would probably be a great source for images:
https://www.pentaxforums.com/forums/122-lens-clubs/86234-15mm-limited-controls-my-mind-club.html

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07-29-2015, 09:44 AM   #3
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QuoteOriginally posted by Adam Quote
Could you please delete this Adam? Can't seem to be able to do it on this side.
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07-29-2015, 10:15 AM   #4
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Pentax SMC-DA 15mm f/4 AL ED Limited - Review / Test Report - Analysis is a good review to start with . From personal experience, the distortion is easy to correct in LR and is quite mild. The distortion though is not perfectly barrel, so may cause some small issues if you are stickler for perfectly straight diagonal lines in a shot.

07-29-2015, 10:34 AM   #5
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QuoteOriginally posted by y0chang Quote
Pentax SMC-DA 15mm f/4 AL ED Limited - Review / Test Report - Analysis is a good review to start with . From personal experience, the distortion is easy to correct in LR and is quite mild. The distortion though is not perfectly barrel, so may cause some small issues if you are stickler for perfectly straight diagonal lines in a shot.
I am actually wanting as much perspective distortion as possible for the cool effect

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Randy
07-29-2015, 10:36 AM   #6
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07-29-2015, 10:38 AM   #7
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QuoteOriginally posted by slip Quote
I am actually wanting as much perspective distortion as possible for the cool effect

Thanks

Randy
Perspective distortion "for the cool effect" is not an intrinsic property of the lens, just a side-effect of your choice of distance from your subject.
A 50mm and a 15mm will both have that same perspective distortion if you shoot the same subject from the same distance, only with the 50mm you'll get a detail, with the 15mm the whole figure.
But it's only a matter of field of view.

Barrel or pincushion distortion OTOH is an intrinsic property of the lens, but most of the time it's hardly noticeable in real world use cases (ie. not brick walls )
07-29-2015, 06:48 PM   #8
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Here are a couple examples from my first outing with the DA 15 limited from a little over 2 years ago. It didn't disappoint.




07-29-2015, 07:02 PM   #9
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QuoteOriginally posted by LensBeginner Quote
Perspective distortion "for the cool effect" is not an intrinsic property of the lens, just a side-effect of your choice of distance from your subject.
A 50mm and a 15mm will both have that same perspective distortion if you shoot the same subject from the same distance, only with the 50mm you'll get a detail, with the 15mm the whole figure.
But it's only a matter of field of view.

Barrel or pincushion distortion OTOH is an intrinsic property of the lens, but most of the time it's hardly noticeable in real world use cases (ie. not brick walls )
Well, perspective distortion is an intrinsic property of the angle of view, so it is related to the lens/camera combination (assuming you don't crop the photo), but one 15mm should be pretty much like any other for this purpose.
07-30-2015, 02:51 AM   #10
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A property of the field of view and the rectilinearity of the lens, one would think. The more firmly square the optics are, the less distortion you get. Compare 10-17 fisheye vs the 12-17 portion of the rectilinear 12-24 or the 15.
07-30-2015, 11:51 AM   #11
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QuoteOriginally posted by pathdoc Quote
A property of the field of view and the rectilinearity of the lens, one would think. The more firmly square the optics are, the less distortion you get. Compare 10-17 fisheye vs the 12-17 portion of the rectilinear 12-24 or the 15.
All theses lenses have quite heavy distorsion at the same focal lense but the distorsion is not the same.
07-30-2015, 12:39 PM   #12
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I think people are getting lens distortion mixed up with perspective distortion. Lens distortion is when the lens makes lines curved when they are straight. Barrel, pincushion, and mustache distortion are examples of this. The first two are easily corrected in LR, but you lose corner resolution when you stretch out the images and the more you stretch it out the more resolution you lose. The most extreme example of barrel distortion is a fisheye lens. The DA 15 has a mild but non-linear lens distortion characteristic. you can see the corners curve more than the center. Perspective distortion is when depending on your angle of shot, things are distorted in size due to the field of view of the lens. Wide angle lens push the background away and bring the foreground closer. This makes dramatic diagonal lines in many compositions. The DA 15 is a wide angle but it is not as wide as a 10mm rectangular lens. You can still get dramatic angles depending on how close you get to your foreground subject.
07-30-2015, 12:47 PM   #13
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QuoteOriginally posted by y0chang Quote
I think people are getting lens distortion mixed up with perspective distortion. Lens distortion is when the lens makes lines curved when they are straight. Barrel, pincushion, and mustache distortion are examples of this. The first two are easily corrected in LR, but you lose corner resolution when you stretch out the images and the more you stretch it out the more resolution you lose. The most extreme example of barrel distortion is a fisheye lens. The DA 15 has a mild but non-linear lens distortion characteristic. you can see the corners curve more than the center. Perspective distortion is when depending on your angle of shot, things are distorted in size due to the field of view of the lens. Wide angle lens push the background away and bring the foreground closer. This makes dramatic diagonal lines in many compositions. The DA 15 is a wide angle but it is not as wide as a 10mm rectangular lens. You can still get dramatic angles depending on how close you get to your foreground subject.
Exactly
07-30-2015, 02:19 PM   #14
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QuoteOriginally posted by y0chang Quote
I think people are getting lens distortion mixed up with perspective distortion. Lens distortion is when the lens makes lines curved when they are straight. Barrel, pincushion, and mustache distortion are examples of this. The first two are easily corrected in LR, but you lose corner resolution when you stretch out the images and the more you stretch it out the more resolution you lose. The most extreme example of barrel distortion is a fisheye lens. The DA 15 has a mild but non-linear lens distortion characteristic. you can see the corners curve more than the center. Perspective distortion is when depending on your angle of shot, things are distorted in size due to the field of view of the lens. Wide angle lens push the background away and bring the foreground closer. This makes dramatic diagonal lines in many compositions. The DA 15 is a wide angle but it is not as wide as a 10mm rectangular lens. You can still get dramatic angles depending on how close you get to your foreground subject.
My point exactly.
07-30-2015, 04:19 PM   #15
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QuoteOriginally posted by y0chang Quote
I think people are getting lens distortion mixed up with perspective distortion. Lens distortion is when the lens makes lines curved when they are straight. Barrel, pincushion, and mustache distortion are examples of this. The first two are easily corrected in LR, but you lose corner resolution when you stretch out the images and the more you stretch it out the more resolution you lose. The most extreme example of barrel distortion is a fisheye lens. The DA 15 has a mild but non-linear lens distortion characteristic. you can see the corners curve more than the center. Perspective distortion is when depending on your angle of shot, things are distorted in size due to the field of view of the lens. Wide angle lens push the background away and bring the foreground closer. This makes dramatic diagonal lines in many compositions. The DA 15 is a wide angle but it is not as wide as a 10mm rectangular lens. You can still get dramatic angles depending on how close you get to your foreground subject.
To me this just a question on how you want to project the image into the sensor plane.

As long as the projection is not the same as our eyes have naturally and our brain intepret, this will look un-natural, distorted.

Even if you choose a rectilinear projection, a human on the border of the picture will look distorted and quite unatural... it might look more natural indeed on a fisheyes projection even through the lines are curved. But say if we speak of buildings and architecture, maybre a rectilinear lense is better because we think that the building should have straight lines, like in reality. In both cases, this is an artistic choice.

For moderate WA, like a 35mm on FF, a rectilinear look quite natural for building and so own and look quite good still on other objects if they are not near. For quite extreme WA, or UWA, this is another story and would be a case by case basis and I can assure you can improve the image by playing with the projection used, even if you come from a perfect rectilinear lense. That's actually why the options are there in your post processing software... Not just to correct lenses.

Last edited by Nicolas06; 07-30-2015 at 04:24 PM.
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