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Author Topic: progessive stretch  (Read 14497 times)
marc gerritsen
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« on: May 15, 2010, 06:18:38 AM »
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you have a tilt shift camera and you fiddle about to get everything into the right plane on location or you don’t have one and you do it in post

either way your building is going to look very pointy on the top or your interior might have proportionally  too much ceiling

in post though you can deal with both the perspective and also the disproportion of size

i have devised a way around that by using “progressive stretch”

how this works is that I divide the photo in increments

lets say i select the bottom 95% of the photo and stretch it by 5%

then the bottom 90% stretched again by 5%

i keep doing this until  i reach the bottom  

as you can see in the samples the the building which is progressively stretched isn't as "pointy" as the one which was just stretched

the windows progressively become smaller towards the top which ads to a more natural look

also the lobby shot which was progressively stretched, looks more natural as the top half and the bottom half are now in proportion

for those who think they don't want more work in post; it took 15 secs to straighten the photo vertically and a push of a button to set an action into motion for the progressive stretch.

for those who think that the photo would fall apart, think pixel interpolation; yes, you will end up with a lesser quality photo, but if you start off with a 110 mb tif file you can still end up with a 70mb tack sharp photo  

the samples and actions are just a first try and need to be perfected so please critique the way of working but not  the photo ....... as yet.

maybe i am barking up the wrong tree and there is software available that can do all this, but my extensive search has failed to come up with something

cheers
marc

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Dick Roadnight
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« Reply #1 on: May 15, 2010, 07:48:31 AM »
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Quote from: marc gerritsen
you have a tilt shift camera and you fiddle about to get everything into the right plane on location or you don’t have one and you do it in post

either way your building is going to look very pointy on the top or your interior might have proportionally  too much ceiling
You do not get the problem if you use movements... if you keep the sensor parallel to a rectangular building, it looks rectangular in the picture...

In your skyscraper shot, if the top of the building in the foreground comes opposite a point h% up the building behind (or the hth floor of a 100 floor building) that is how it will look (as a proportion of picture height, using shift to keep parallel) in the picture.

The unnatural look you get is the result of stretching the whole picture, and you (attempted to compensate) with progressive stretching.

Unfortunately, your technique makes square windows look rectangular in the upper floors.

It would be possible to correct the barrel distortion in the interior picture (bent ceiling line)... this would be a PITA, but it would increase the apparent height of the far corner of the room.

Does anyone know of any decent software to do this? Last time I tried it in PS you had to extend the picture so that the distortion was symmetrical (so that the fattest part of the barrel was in the middle of the picture) and in this case you would also have to split the picture in two.
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marc gerritsen
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« Reply #2 on: May 15, 2010, 08:00:58 AM »
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Quote from: Dick Roadnight
Unfortunately, your technique makes square windows look rectangular in the upper floors.

It would be possible to correct the barrel distortion in the interior picture (bent ceiling line)... this would be a PITA, but it would increase the apparent height of the far corner of the room.


when you look at the unstretched photo the windows appear rectangular because they are further away from the viewer
i have done the same with the progressive stretch to create a more natural look

as far as the interior photo is concerned there is no barrel distortion as phocus certainly has taken care of it
so don't understand your comment there
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marc gerritsen
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« Reply #3 on: May 15, 2010, 08:14:21 AM »
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when you look at this photo which was shot with a camera with movements
i find that the top of the building is way overstretched
and when you look at the different sections ticked in red
they are all the same size which is unnatural as the top sections should be smaller then the bottom sections
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adammork
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« Reply #4 on: May 15, 2010, 10:09:59 AM »
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Quote from: marc gerritsen
when you look at this photo which was shot with a camera with movements
i find that the top of the building is way overstretched
and when you look at the different sections ticked in red
they are all the same size which is unnatural as the top sections should be smaller then the bottom sections

Dear Marc,

To my eyes as an architect and arch. photographer, your progressive stretch simply destroys the proportions of the building..... it completely looks like the height of the floors are decreasing at the top - also, in the other image, the height of the round furniture looks quit tall, of course I have not seen them in real life - and again it's to my eyes  

the last example shows, that this was maybe not the best viewpoint for this building.... I know - this could be the only spot were the camera could stand  

very best,
adam
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fredjeang
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« Reply #5 on: May 15, 2010, 10:16:04 AM »
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Quote from: adammork
Dear Marc,

To my eyes as an architect and arch. photographer, your progressive stretch simply destroys the proportions of the building..... it completely looks like the height of the floors are decreasing at the top - also, in the other image, the height of the round furniture looks quit tall, of course I have not seen them in real life - and again it's to my eyes  

the last example shows, that this was maybe not the best viewpoint for this building.... I know - this could be the only spot were the camera could stand  

very best,
adam
Yes, I do have the same impression. When it comes to crucial details that's where the problems start.
Acheiving such perfection in PP is then a long task.
At the end, as I've asked before here, nothing seems today able to replace a proper view camera.
Maybe in a close future.
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JeffKohn
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« Reply #6 on: May 15, 2010, 10:16:18 AM »
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Quote from: marc gerritsen
when you look at this photo which was shot with a camera with movements
i find that the top of the building is way overstretched
and when you look at the different sections ticked in red
they are all the same size which is unnatural as the top sections should be smaller then the bottom sections
The problem with this shot is that you're just too close; the FOV is too wide for a natural looking rectilinear perspective and there also could be some barrel distortion to make things worse. The best "fix" for this situation would be to back up a little, but of course that's no always possible. Sometimes when you're really close, tilting the camera up just enough to add a very small amount of keystoning will look more natural, because when we look at a building from that close in person we see some keystoning.
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JoeKitchen
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« Reply #7 on: May 15, 2010, 10:30:08 AM »
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Quote from: marc gerritsen
when you look at the unstretched photo the windows appear rectangular because they are further away from the viewer
i have done the same with the progressive stretch to create a more natural look

I am pretty sure that this effect you only get if you are correcting the perspective in PS and not optically.  If you are parallel to a plane (or line) no matter how any 2 dimensional object (or 1 dimensional for a line) is moved about that plane, the object is not going to change shape.  In the image I have below, the vertical perspective was corrected optically and all of the windows have the same proportion throughout the building (of course you need to compare windows in the same column since there is horiz distortion).  Now I know there is horizontal perspective distortion but try to ignore that.  All of the vertical lines on the windows (from the ones that are similar in real life) are equal throughout the image.  I am sure if you find the area of each parallelogram formed from the windows in the image they will all be the same thus proving the proportions are equal.  

For you first image, it just does not look right and I cant go into any further detail then that.  Also, I am sure in the high res image the building appears less sharp at the top, something you would not get (or get as much since sharpness does falloff towards the edge of the circle) if you corrected optically.  

For the last image you showed (which was corrected optically) that distortion is from the falling off effect you get from the edge of the image circle on wide lenses.  If you could, stand further back and use a longer lens, or elevate yourself to a good height.
« Last Edit: May 15, 2010, 10:34:21 AM by JoeKitchen » Logged

Joe Kitchen
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"Photography is one percent inspiration and ninety-nine percent moving furniture."  Arnold Newman
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rsmphoto
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« Reply #8 on: May 15, 2010, 10:42:56 AM »
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Actually Marc, I totally agree with you and it is an inherent issue when using movements. The light simply has further to travel to the edges of the film/chip plane and the image gets distorted. Buildings, no matter how tall, when shot close with a wide lens look extremely top heavy and it's been a peeve of mine for years. I've used similar solutions to yours at times in the past - this is more an art, than a science, right? You do what you think is right for your particular image. I don't find this so much an issue with interiors, but from time to time...  All-in-all I agree with your thinking.
« Last Edit: May 15, 2010, 11:08:56 AM by rsmphoto » Logged
Dick Roadnight
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« Reply #9 on: May 15, 2010, 01:24:08 PM »
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Quote from: marc gerritsen
as far as the interior photo is concerned there is no barrel distortion as phocus certainly has taken care of it
so don't understand your comment there
Phocus is great, but to my eye, the ceiling line looks bent.
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« Reply #10 on: May 15, 2010, 04:09:24 PM »
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This is an odd discussion. Are you trying to capture the building as it really is? If you are using a view camera, this is the only way to do this accurately. Whether you think you see a buildings windows on the upper floor differently than the lower floors, it doesn't matter. In this example and in reality, the windows are the same size. Stretching them might feel good to you, but it's creating something that doesn't exist. Its just another way of making a building look like its falling backward.
« Last Edit: May 15, 2010, 04:12:18 PM by JonathanBenoit » Logged

CBarrett
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« Reply #11 on: May 15, 2010, 04:40:06 PM »
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While I find the decreasing window size in the shot of the building unsettling ( I prefer the "stretch the photo vertical" version).  I've really got to applaud not just the fact that Marc is so creatively inventive, but that he is willing to share the results with us.  That building could obviously not have been shot from that distance with a perspective control camera (or lens) while capturing the full height.

Here comes an interesting dilemma...  The interpolation introduced in some applications of this technique might send some of us pixel peepers running for the hills, but if you're client is only ever going to use it on the web and in powerpoints AND the shot simply cannot be achieved with a plumb and level camera.... then get the friggin shot however you can and fix it!

For 99% of my work the image circles of my lenses accomplish what I need to do while keeping my camera quite parallel to mother earth, but 1% of the time....

Nice work, Marc.
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marc gerritsen
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« Reply #12 on: May 15, 2010, 06:09:58 PM »
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thanks chris!

the building shot is indeed taken too close there was no way to go further back or go up
when i gave the photo to my client i did not do anything to it, i only used this building shot to demonstrate something,
as for as the building is concerned this might not be a good solution, must also agree with jonathan that the building
looks like it is leaning backwards a bit in the progressive stretch

as for as the interior shot i do think this is an improvement overall, as the bottom part and the top part are now more in proportion
i normally do not shoot interiors like that but in this case the focus is on the the glass sculpture hanging of the ceiling
so the only way is to shoot upwards (btw this is the largest glass sculpture in the world and runs the length of 84 m by nikolas weinstein)
and again there is no barrel distortion, if there is a perceived curving it is real, either the builders or the designers have done it but not the camera
i have tested phocus and flexcolor at nausea for this

anyway just wanted to share my rough findings of yesterday, i was really excited as i thought i was on to something,
i have never seen anybody do a progressive stretch
will certainly will do more refinement for the interiors but will leave the buildings alone

cheers
m
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rethmeier
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« Reply #13 on: May 15, 2010, 06:36:20 PM »
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I agree with Chris!
Well done Marc.
Cheers,
Willem.

N.B Isn't there something in CS5 that does something like that?
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Willem Rethmeier
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Hening Bettermann
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« Reply #14 on: May 15, 2010, 07:11:16 PM »
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Quote from: marc gerritsen
there is software available that can do all this, but my extensive search has failed to come up with something

When looking for a software that could correct perspective by the numbers (of degrees of camera tilt), I found Digital Photo Shifter:

http://www.deraltenburger.de/Win-Tools/Index.html

It can do what I wanted, with or without proportional compressing of the upper part of high vertical objects. (The latter is what you want, if I got it right).

The tool comes in different versions:
1-as a standalone Windows app,
2-as a plug-in for PS
3-as a plug-in for FixFoto,
4-as a plug-in for the Windows version of PhotoLine

http://www.pl32.com/

Only #4 offers 16 bit color depth. - German only...and I found the surface rather confusing.

Good light - Hening.
« Last Edit: May 15, 2010, 07:32:53 PM by Hening Bettermann » Logged

Kirk Gittings
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« Reply #15 on: May 15, 2010, 07:37:50 PM »
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Quote
Here comes an interesting dilemma... The interpolation introduced in some applications of this technique might send some of us pixel peepers running for the hills, but if you're client is only ever going to use it on the web and in powerpoints AND the shot simply cannot be achieved with a plumb and level camera.... then get the friggin shot however you can and fix it!

Words of wisdom......
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Thanks,
Kirk

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marc gerritsen
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« Reply #16 on: May 15, 2010, 08:03:44 PM »
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Quote from: Kirk Gittings
Words of wisdom......


yes but


this was an other test i have done to see exactly what happens with those interpolated pixels and realized that i can use this technique not just for power point and web
but print as well even used this shot on the front cover of a local developers magazine

A to E my 5-step perspective technique and G and H 100% comparison crops from before and after
when you look at the crops you will see that full page print would be easily achievable

what i do agree with 100% is to get the frigging shot anyway you can, make that client happy and get paid!!!
cheers
m
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marc gerritsen
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« Reply #17 on: May 15, 2010, 08:08:40 PM »
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this is a better crop of the edge
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emcphoto
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« Reply #18 on: May 15, 2010, 08:35:02 PM »
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Hi Marc,

I am interested in trying out your method, do you mind explaining it in more detail?

Thanks!
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Kirk Gittings
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« Reply #19 on: May 15, 2010, 10:28:16 PM »
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For new AP's......let me say also that sometimes......sometimes the best solution is NOT to correct the convergence and make the composition work without perspective correction. The cover of Antoine Predock's new Rizzoli monograph-Volume 5.

[attachment=22017:rizzoli5.jpg]
« Last Edit: May 15, 2010, 10:31:41 PM by Kirk Gittings » Logged

Thanks,
Kirk

Kirk Gittings
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