Something to ponder!
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Posted 25/11/2013 - 10:42
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Having sat through the theory lessen I took ChrisA's advice and did the practical. Well, proof is in the pudding as they say! I must admit, I had noticed the bit about moving position, but thought that it couldn't make that much difference.
No full-frame for me!!
No full-frame for me!!
Posted 25/11/2013 - 10:45
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Algernon wrote:
The 85mm will be a magnified view irrespective of format.
The 50mm will be a less magnified view.
Yes.The 85mm will be a magnified view irrespective of format.
The 50mm will be a less magnified view.
But magnification does not change perspective, because everything in the image is magnified by the same amount.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Posted 25/11/2013 - 10:52
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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.
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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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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 25/11/2013 - 10:58
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Algernon wrote:
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.
Cobblers.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.
The perspective lines are nearly parallel because the horse is a long way away.
Take a 100mm macro lens, for instance. It has the same focal length (and hence magnification) as a 100mm non-macro lens. But its mechanism allows it to focus a lot closer, in which case, once you get closer (and not otherwise), your perspective lines are less parallel.
I shall say no more. Hopefully the rest of the forum won't fall for all this claptrap.
Why don't you do the experiment that Tony did?
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Posted 25/11/2013 - 11:21
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Here are the pics (not on a tripod, but on a table, so probably a slight movement on changing lenses - I have to work you know!):
10mm (heavily cropped)
200mm (needed to use f/32 and high iso to get dof)
That Sigma 10-20 is bl**dy good, innit !
10mm (heavily cropped)
200mm (needed to use f/32 and high iso to get dof)
That Sigma 10-20 is bl**dy good, innit !
Posted 25/11/2013 - 11:23
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Honestly, it is very interesting - includes a nice equation !
Posted 25/11/2013 - 11:24
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Fletcher8 wrote:
JAK, I was only referring to ISO and shutter in relation to creating the same image in relation to how it would look, but I had not thought about the horizontal angle and the diagonal field of view measurements.
Changing the ISO, shutter speed and aperture would only affect the depth of field (ie how much looks to be in focus) but not the field of view.JAK, I was only referring to ISO and shutter in relation to creating the same image in relation to how it would look, but I had not thought about the horizontal angle and the diagonal field of view measurements.
I mentioned the different ways of showing field of view because manufacturers / retailers are not consistent as to which angle they refer to. Some camera makers (not all) confuse the matter further on small compact cameras by showing the focal lengths on the camera as 35mm equivalents without making that fact clear. If the focal lengths indicated were true the lens would have extreme telephoto properties!
ChrisA, the key point in that PhotoZone article is
Quote:
so I moved my position according to the focal length as opposed to "zooming"
so the article is completely correct as the examples show.so I moved my position according to the focal length as opposed to "zooming"
John K
John K
Posted 25/11/2013 - 11:33
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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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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 25/11/2013 - 11:37
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Gary 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 !
Posted 25/11/2013 - 11:37
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JAK wrote:
ChrisA, the key point in that PhotoZone article is
I know it says that. But at the very beginning of the article it says:ChrisA, the key point in that PhotoZone article is
Quote:
so I moved my position according to the focal length as opposed to "zooming"
so the article is completely correct as the examples show.so I moved my position according to the focal length as opposed to "zooming"
[quote="complete berk"]The following slide show illustrates the effect of different focal length on the perspective.[/quote]Which it very much does not.
It illustrates how the perspective changes when you walk around.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Posted 25/11/2013 - 11:46
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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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Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Pentax K-1 + K-5 and some other stuff
Algi
Posted 25/11/2013 - 11:58
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TonyM wrote:
which probably won't help your portraits (big nose!)
You wouldn't get the "big nose" because the subject would be far enough to make the nose appear in approximately the same plan as the cheeks and eyes.
which probably won't help your portraits (big nose!)
Yves (another one of those crazy Canucks)
Posted 25/11/2013 - 12:02
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Yep, get that now. Am I correct in thinking that dof will change though, i.e. f/8 will give a different dof if you crop the full frame image to the same fov as the APS-C?
Posted 25/11/2013 - 12:09
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TonyM wrote:
Y Am I correct in thinking that dof will change though,
The DOF will be the same if you use the same aperture and you stand at the same place, irrelevant of focal length. Cropping will be different, and details will be lost due to cropping, but everything else will be identical.
Y Am I correct in thinking that dof will change though,
Yves (another one of those crazy Canucks)
119 posts
18 years
Lincolnshire
Interesting.