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05-18-2016, 07:17 AM   #991
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QuoteOriginally posted by house Quote
When the field of view is identical the perspective and compression is identical?

Switching lens/sensor combo for the same field view results in identical perspective.
Imagine you are standing in front of a very wide palace, at a distance of 120 feet, and there is a row of flags in front of the palace, from the left end to the right end.

Without moving from your spot, say you want to capture a photo of the palace, and have each flag in the picture. Say you use an 85mm lens, and you're using a film camera.

Now you step up closer to the palace by 100ft, so you're now only 20ft away from the palace. To get every flag in again, you probably need an 20mm lens now.

Now compare the photos taken. They both include all the flags, from left to right. But they look very different. In order for the 20mm lens to squeeze in every flag, at such a close distance to the palace, it would have to distort the perspective. Diverging lines for example, would diverge very dramatically, more so than in real life.

So the 20mm lens, a wideangle, as compared to 85mm, introduces a visible form of distortion (which can actually look very nice when used right).

The key point here is that a wideangle lens, by its very design, introduces perspective distortion to an image that it casts.

Now, consider using an FA31 to snap a given scene, with a given FOV. Assume you're using an APS-C sensor now, eg. with a K-3. In fact, the image being captured (and also what is seen in the viewfinder) is just a crop, a portion, of the real, larger image being cast by the lens. Hence we're only seeing a part of the real picture; the effect is the same as cropping away the edges of a picture, and then magnifying the remaining portion until it comes back to the original size of the image before being cropped. In other words, there is magnification going on, of the middle uncropped portion of the picture. Or to put it another way, in APS-C, the FOV has been narrowed. That is, the FOV feels the same as if we were using an FA43 on a Full-frame sensor (here the entire image cast by the lens is captured/seen - no cropping).

So the FOV appears the same, but remember that the image cast by the 31, it being a wideangle lens, would inherently have that distortion effect (although milder than that seen in a 20mm).

Whereas an FA43, being a true-normal, does not generate this distortion effect.

Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.


Last edited by KDAFA; 05-18-2016 at 07:38 AM.
05-18-2016, 07:17 AM   #992
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QuoteOriginally posted by noelpolar Quote
I was quite surprised how well it handled the water (non pixel shifted version is in my flickr stream)
Did you process that in DCU or was it an OOC Jpeg?
05-18-2016, 07:23 AM - 1 Like   #993
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FF Mode • 100 ISO • Sigma Art 18-35mm F1.8 DC HSM
05-18-2016, 07:24 AM   #994
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QuoteOriginally posted by Zen4Life Quote
Did you process that in DCU or was it an OOC Jpeg?
Dcu to tiff to Lr to dxo filmpak

05-18-2016, 07:54 AM   #995
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QuoteOriginally posted by KDAFA Quote
Imagine you are standing in front of a very wide palace, at a distance of 120 feet, and there is a row of flags in front of the palace, from the left end to the right end.

Without moving from your spot, say you want to capture a photo of the palace, and have each flag in the picture. Say you use an 85mm lens, and you're using a film camera.

Now you step up closer to the palace by 100ft, so you're now only 20ft away from the palace. To get every flag in again, you probably need an 20mm lens now.

Now compare the photos taken. They both include all the flags, from left to right. But they look very different. In order for the 20mm lens to squeeze in every flag, at such a close distance to the palace, it would have to distort the perspective. Diverging lines for example, would diverge very dramatically, more so than in real life.

So the 20mm lens, a wideangle, as compared to 85mm, introduces a visible form of distortion (which can actually look very nice when used right).

The key point here is that a wideangle lens, by its very design, introduces perspective distortion to an image that it casts.

Now, consider using an FA31 to snap a given scene, with a given FOV. Assume you're using an APS-C sensor now, eg. with a K-3. In fact, the image being captured (and also what is seen in the viewfinder) is just a crop, a portion, of the real, larger image being cast by the lens. Hence we're only seeing a part of the real picture; the effect is the same as cropping away the edges of a picture, and then magnifying the remaining portion until it comes back to the original size of the image before being cropped. In other words, there is magnification going on, of the middle uncropped portion of the picture. Or to put it another way, in APS-C, the FOV has been narrowed. That is, the FOV feels the same as if we were using an FA43 on a Full-frame sensor (here the entire image cast by the lens is captured/seen - no cropping).

So the FOV appears the same, but remember that the image cast by the 31, it being a wideangle lens, would inherently have that distortion effect (although milder than that seen in a 20mm).

Whereas an FA43, being a true-normal, does not generate this distortion effect.

Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.


Great explanation.

It's like somebody took all my lenses away one night and added some mystical element to them.

The only downside is it feels like my 300mm got shorter even though I know I can crop it to get exactly the same FOV.
05-18-2016, 07:58 AM - 1 Like   #996
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QuoteOriginally posted by KDAFA Quote
Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.
This is getting OT but perspective distortion is a property of distance to subject not FL of lens. So standing in the same spot and changing both sensor and lens for equivalent field if view should give identical perspective.
05-18-2016, 08:00 AM   #997
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QuoteOriginally posted by KDAFA Quote
Imagine you are standing in front of a very wide palace, at a distance of 120 feet, and there is a row of flags in front of the palace, from the left end to the right end.

Without moving from your spot, say you want to capture a photo of the palace, and have each flag in the picture. Say you use an 85mm lens, and you're using a film camera.

Now you step up closer to the palace by 100ft, so you're now only 20ft away from the palace. To get every flag in again, you probably need an 20mm lens now.

Now compare the photos taken. They both include all the flags, from left to right. But they look very different. In order for the 20mm lens to squeeze in every flag, at such a close distance to the palace, it would have to distort the perspective. Diverging lines for example, would diverge very dramatically, more so than in real life.

So the 20mm lens, a wideangle, as compared to 85mm, introduces a visible form of distortion (which can actually look very nice when used right).

The key point here is that a wideangle lens, by its very design, introduces perspective distortion to an image that it casts.

Now, consider using an FA31 to snap a given scene, with a given FOV. Assume you're using an APS-C sensor now, eg. with a K-3. In fact, the image being captured (and also what is seen in the viewfinder) is just a crop, a portion, of the real, larger image being cast by the lens. Hence we're only seeing a part of the real picture; the effect is the same as cropping away the edges of a picture, and then magnifying the remaining portion until it comes back to the original size of the image before being cropped. In other words, there is magnification going on, of the middle uncropped portion of the picture. Or to put it another way, in APS-C, the FOV has been narrowed. That is, the FOV feels the same as if we were using an FA43 on a Full-frame sensor (here the entire image cast by the lens is captured/seen - no cropping).

So the FOV appears the same, but remember that the image cast by the 31, it being a wideangle lens, would inherently have that distortion effect (although milder than that seen in a 20mm).

Whereas an FA43, being a true-normal, does not generate this distortion effect.

Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.
It's not the lens, it's the distance.

Do a Brenizer with a longer focal length and it will look exactly the same as a wide angle shot (if you shoot from the same spot and match the FoV); take a cropped wide angle and a tele and they will again look the same (again matching shooting point and FoV).

Edit: as house said.
05-18-2016, 08:36 AM   #998
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Hi guys,

Thanks to all who responded, and for correcting my error. But, as a few have already mentioned, this could end up running this thread off-topic, so best to stop it here. It is after all a picture-posting thread.

Cheers.


Last edited by KDAFA; 05-18-2016 at 09:04 AM.
05-18-2016, 09:26 AM   #999
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It's made my head hurt thinking about it. But I think I see that house's logic is indisputable.
05-18-2016, 09:55 AM - 1 Like   #1000
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My first attempt at pixel shift. D-FA f2.8 100mm macro iso100 1/30 sec at f5.6. Developed in PDCU with lens corrections to auto. Saved as an 8 bit tiff - processed in Elements 9.0. (Changed from adobeRGB to sRGB for web and reduced pixels for forum. ) The auto lens corrections do a great job; the purple fringing so visible in a straight raw of this shot vanished in this version.

Platinum Diamonds and Amethysts
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Last edited by HoustonBob; 05-18-2016 at 10:29 AM.
05-18-2016, 10:07 AM - 5 Likes   #1001
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Took a walk with the K1 here this morning. K1 + 28~105.
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05-18-2016, 10:53 AM - 1 Like   #1002
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QuoteOriginally posted by KDAFA Quote
So the FOV appears the same, but remember that the image cast by the 31, it being a wideangle lens, would inherently have that distortion effect (although milder than that seen in a 20mm).

Whereas an FA43, being a true-normal, does not generate this distortion effect.

Bottom line, the FOV appears the same, but the FA31 image has that perspective distortion effect in it.
EDIT: I just noticed that other people already corrected this, but I'll just leave this here for anyone interested in a more detailed explanation of perspective and "wide angle distortion", as this misconception is quite common.

Perspective is entirely controlled by distance. If A and B are the same size, but B is twice as far as A, B will look half the size of A. It's that simple. No properties of lenses or cameras, just pure geometry. Compare the same two objects, and you will find the ratio of their sizes are the same for any rectilinear lens (or your own naked eyes) when shot from the same distance and orientation.

"Wide angle distortion" (objects on the edge of the frame look bigger/stretched compared to the center) is a property of "rectilinear" (gnomonic) projection, and is controlled purely by angle of view in rectilinear lenses. It is a result of mapping a spherical scene onto a flat plane. As the angle approaches 180 degrees, the distortion (stretching) approaches infinity. All rectilinear lenses display this property, just that the size difference between the center and the edges only becomes noticeable as you get very wide. If you've ever seen a video game that lets you dynamically adjust FOV (AOV), you will see this is a property of the geometric projection, not of any lens in particular.

Last edited by Cannikin; 05-18-2016 at 11:24 AM.
05-18-2016, 11:25 AM - 1 Like   #1003
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Others have said it, but if you shoot from the distance on APS-C and full frame with equivalent lenses, you will have the same shot. I'll have to post a couple of examples, but it is hard to get my kids to hold still long enough to do so.

This is a shot with the DA *55 wide open.

Elliot.

05-18-2016, 11:28 AM - 14 Likes   #1004
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K-1 and 150-450

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05-18-2016, 11:32 AM - 3 Likes   #1005
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Beautiful bird shots Philip!

The K-1 does red. With the D FA 28-105 @ 105mm, center crop, ISO 1600.
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