All Forum Comments
Comment by Algernon posted on Something to ponder! at 25/11/2013 - 18:09
Perhaps a quick rough sketch will demonstrate that the Photozone
article is correct..... at least for the brighter Pentax Users
The sketch shows a WA shot and a Tele shot looking down a road.
Note the kerbline angles stay the same all the way to the vanishing
point (which isn't shown here). Therefore each lens produces it's
own individual perspective view and you can't obtain one picture
from the other by cropping. The format (FF or APS-C)
wouldn't change the kerb angles either.
The WA lens kerblines always converge faster than the
Tele kerblines which become closer to parallel with
longer Teles.
Moving the camera providing you stay on the centerline
won't make any difference.
If you can't see it from the sketch.... try it yourself with a
camera and two lenses (or a zoom).
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article is correct..... at least for the brighter Pentax Users
The sketch shows a WA shot and a Tele shot looking down a road.
Note the kerbline angles stay the same all the way to the vanishing
point (which isn't shown here). Therefore each lens produces it's
own individual perspective view and you can't obtain one picture
from the other by cropping. The format (FF or APS-C)
wouldn't change the kerb angles either.
The WA lens kerblines always converge faster than the
Tele kerblines which become closer to parallel with
longer Teles.
Moving the camera providing you stay on the centerline
won't make any difference.
If you can't see it from the sketch.... try it yourself with a
camera and two lenses (or a zoom).
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Comment by Algernon posted on Something to ponder! at 25/11/2013 - 17:20
TonyM wrote:
OK, am I thinking of sensor size then? I.e. dof for any given lens on APS-C is greater at a specific aperture than the full-frame?
That's correct.... One of the few advantages of FF is that theOK, am I thinking of sensor size then? I.e. dof for any given lens on APS-C is greater at a specific aperture than the full-frame?
same shots have a shallower DOF. If you want more DOF FF
becomes a disadvantage.
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Comment by Algernon posted on Something to ponder! at 25/11/2013 - 12:31
TonyM wrote:
The person who wrote that article must believe that a telephotoGary Hickin wrote:
Honestly, it is very interesting - includes a nice equation !
Indeed it is, and the key quote is: "two shots of the same scene from the same distance will exhibit identical perspective distortion, regardless of lens used"Honestly, it is very interesting - includes a nice equation !
lens isn't a magnifier In other words... That's garbage
There were some excellent photos on the Talk Photography Forum
demonstrating this, but I can't fine them
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Comment by Algernon posted on Something to ponder! at 25/11/2013 - 11:46
There's a very good example of compression/magnification
at the very bottom of the page Gary linked to.....
http://en.wikipedia.org/wiki/Perspective_distortion_(photography)
link
Direct Link to photo link
It's the building taken with a 300mm lens ....... Only a 300mm
lens can produce that amount of foreshortening because it magnifies....
It can't be done with a 50mm and format does not matter.
http://painting.about.com/od/artglossaryf/g/defforeshorten.htm
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at the very bottom of the page Gary linked to.....
http://en.wikipedia.org/wiki/Perspective_distortion_(photography)
link
Direct Link to photo link
It's the building taken with a 300mm lens ....... Only a 300mm
lens can produce that amount of foreshortening because it magnifies....
It can't be done with a 50mm and format does not matter.
http://painting.about.com/od/artglossaryf/g/defforeshorten.htm
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Comment by Algernon posted on Something to ponder! at 25/11/2013 - 11:33
ChrisA wrote:
The problem with that article is that it's shockingly misleading. The reason the author got the different perspectives is that he moved between shots.
At 17mm he was close to the lamp, so it looked bigger relative to the background than at 100mm, when he would have had to move back to get the lamp to be the same size on his image.
If he had stood in the same place, taken images at different focal lengths, and then cropped out appropriate bits to compare the perspectives, he would have found that the perspective was exactly the same in each one.
Don't take my word for it, try it!!
I don't know why you bring up the subject of magnifying lenses (I assume you mean, as in magnifying glasses) - they create virtual images not real ones like in a camera.
I can't believe that you don't know what perspective is! Algernon wrote:
I don't believe a word of what Chris has said!
The PhotoZone article is spot on. If it were anything else
a magnifying lens couldn't exist and all optical
science would have to be re-written
The article is self explanitory.
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Algy, at risk of getting my wrists slapped by JR, you're a numpty (and/or a dreadful stirrer!) I don't believe a word of what Chris has said!
The PhotoZone article is spot on. If it were anything else
a magnifying lens couldn't exist and all optical
science would have to be re-written
The article is self explanitory.
--
The problem with that article is that it's shockingly misleading. The reason the author got the different perspectives is that he moved between shots.
At 17mm he was close to the lamp, so it looked bigger relative to the background than at 100mm, when he would have had to move back to get the lamp to be the same size on his image.
If he had stood in the same place, taken images at different focal lengths, and then cropped out appropriate bits to compare the perspectives, he would have found that the perspective was exactly the same in each one.
Don't take my word for it, try it!!
I don't know why you bring up the subject of magnifying lenses (I assume you mean, as in magnifying glasses) - they create virtual images not real ones like in a camera.
If you draw lines from say the top of the lamp to the top of the
church spire and from the bottom of the lamp to the bottom of
the church spire it produces perspective lines and they are
different for each focal length regardless of where you stand.
The 100mm view will produce almost parallel perspective lines
because it is a magnified view. Similar to watching horse
racing on TV the horse only moves slowly towards you because
the distance appears compressed. It's actually the horse that is
magnified.
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Comment by Algernon posted on Something to ponder! at 25/11/2013 - 10:52
The 85mm will be a magnified view irrespective of format.
The 50mm will be a less magnified view. I've never actually
carried out the test to see which lens sees the same as my
eye without any magnification. Quite easy to do.... just
watch how an artist views a scene by holding up a pencil.
They say it's 50mm, but I don't know for sure.
For landscapes you can simulate FF frame by using APS-C in
portrait/vertical orientation and taking 3 shots overlapping
slightly less than half of the frame and stitching.
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The 50mm will be a less magnified view. I've never actually
carried out the test to see which lens sees the same as my
eye without any magnification. Quite easy to do.... just
watch how an artist views a scene by holding up a pencil.
They say it's 50mm, but I don't know for sure.
For landscapes you can simulate FF frame by using APS-C in
portrait/vertical orientation and taking 3 shots overlapping
slightly less than half of the frame and stitching.
--
Comment by Algernon posted on Something to ponder! at 25/11/2013 - 10:29
I don't believe a word of what Chris has said!
The PhotoZone article is spot on. If it were anything else
a magnifying lens couldn't exist and all optical
science would have to be re-written
The article is self explanitory.
--
The PhotoZone article is spot on. If it were anything else
a magnifying lens couldn't exist and all optical
science would have to be re-written
The article is self explanitory.
--
Comment by Algernon posted on Something to ponder! at 25/11/2013 - 10:11
The leaf looks like it's dyed
Comment by Algernon posted on Please remember me at 24/11/2013 - 08:51
I haven't got a moustache even though I should have.....
Algernon is a given name which derives from the Norman-French
soubriquet Aux Gernons, meaning "with moustaches".
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Algernon is a given name which derives from the Norman-French
soubriquet Aux Gernons, meaning "with moustaches".
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Comment by Algernon posted on Another pointless thread at 22/11/2013 - 14:43
all the way back to the vanishing point and the angles will not
alter and they will always be different for a WA and Tele.
In the sketch the WA kerbline is about 40deg off vertical and
the Tele is about 7deg.
One normal use of a WA is distorted faces and bodies such as this
link
You can't get that shot with a Tele and you can't recover normal
perspective from it either there will always be distortion.
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