an oblique view of photographs

25th January 2008, 18:45
In order to get photographs of some plans (with permission)
I have had to take an oblique angle to eliminate reflections from
the glass. Is there any software that can straighten everything
to a rectangle? I know there is a vertical alignment programme,
but it only works one way. To be frank, I can't afford expensive
software, either. I have used the perspective settings on PSP,
with fair results, but I wondered if there was something that
could do it in one fell swoop, or by using the cursor to stretch.
Best Wishes, Raymond

25th January 2008, 21:24
The newer versions of Photoshop supposedly have this facility but are quite expensive (although you can download a 30 day trial version) I suspect that you will be left with some dimensional inaccuracies even with the adjusted version.can you retake the photographs with a polarising filter?


K urgess
25th January 2008, 21:38
Some of the effects in Corel Photopaint will allow you to stretch a picture in any direction you like.
I'm sure there are plenty of software packages out there that will do likewise.
Since expanding the "narrow" end of the picture will make lines appear thicker as they are expanded to fill the space, some sort of conversion to vecotr graphics may be needed first.
Best of luck, Raymond.
You really need to be a whizz at Chinese puzzles to figure out how to do some of these things. [=P]

25th January 2008, 21:48
Thanks Kris ...
To my regret, on occasion, I am a whizz with geometry, trigonometry
and perspective calculation. There have been a number of occasions
when the only way to survey an elevation was to take photographs
and calculate the whole thing. The plans were on board ship, screwed
to the wall. I really do not wish to push my luck too far by asking again.
Best Wishes, Raymond

K urgess
25th January 2008, 21:59
Most of your problem will probably be with the non linear characteristics of the lens.
Attached are two examples showing a perspective stretch by the software I mentioned. Probably a bit simple and not too good an example.
I didn't stretch the second one vertically to compensate for compression.
The subject matter is not a reflection of my attitude to some software packages. [=P]


25th January 2008, 22:30
I see what you mean, as the school report used to say "could do better".

26th January 2008, 09:15
DxO Optics software I have used (demo version) to great effect. Price tag too much for occasional usage ($299).

Otherwise I consistently use the Photoshop 'Distort' function.

26th January 2008, 11:00
Sometimes a polarising filter will do the job.
But be warned there are two types of filter, it depends if you use an SLR or point and shoot.

Gavin Gait
26th January 2008, 11:06
OK I guess your having to use a flash so here's the simple ( and cheap ) way to take photos through glass.
What you need is a cheap generic flash unit ( one that clips onto the top of the camera ) , a hot-shoe adapter ( this should have 2 blocks one to clip onto the camera and one to clip onto the bottom of the flash unit ) and a 1m/3ft connecting cable. Most digital cameras need to have the hot-shoe adapter switched on for the external flash from the settings so do that first.

Hold the flash unit out to one side at a 45' angle across the glass ( put a bit of very thin paper - the type they wrap clothes in - around the flash head to soften the light ) and take the photo square on to the plans. With a bit of experimentation to get the distance from the plans and the angle of the lens you will be able to take photos without the glare of the flash.


Pat Thompson
26th January 2008, 11:19

A cheapo flash brolly might help?????????


Pat Thompson

You can't get enough photos of "O'Boats" (especially if they are well lit!!)

Bob Preston
26th January 2008, 15:11
Photoshop Elements 5. Pull down the "View" menu. Superimpose a grid, then Pull down filters and select "distort". Then play with it by pulling on the various handles.The grid lets you check the accuracy of all horizontals and vertical lines

You can pick up Photoshop Elements 5 for 20 or less on e-Bay, several of my students did only last week.


26th January 2008, 16:17
That sounds a good one, Bob, Thank you ...

Here's a for example ... on side deck ...
screwed to wall, mounted in "glass", window behind me directly opposite the drawing.
I either get a figure of myself framed in the window reflection, or I take it on the oblique.
If I cut the picture into sections and rotate the section so the centre of the image is
horizontal, then using the perspective altering tool, and then alter the image proportion,
it is near right, after a few calculations as to the original size and comparing it with the
size on the image. But, as Kris says, the line thicknesses are also altered. I have the
dimensions of the ship and so can sort most of it out, but it would have been so much
simpler if vector points could be set and just slid around. PSP does have the function,
but only on drawn objects, not photograph images. I think what I will have to do is to
simply print off what I can get and to draw physically the final layout ... I always wanted
to be a marine architect. I also have had to take pictures of plans in a record office, on
the skew because no flash can be used (nor should it be).
Best Wishes, Raymond

26th January 2008, 16:36
Well, I have ordered said Ps Elements from me old mate Amy zon.

K urgess
26th January 2008, 17:27
Tried to straighten out your picture, Raymond.
Not really enough contrast or resolution to convert it to a vector drawing or even remove the glass.
Purely from a rough try, funnily enough in a Serif program that allows unlimited distortion.


26th January 2008, 18:07
That is pretty good, Kris, that is probably the worst
of the images, and it was reduced down to fit SN limits.
Every now and then I simply have to take what is there,
or nothing, and I would rather have the first option and
sort it afterwards. Serif, I may have the CDs here somewhere.
I used to have them on the PC of two eras ago until I got
PSP7 anniversary Ed. There are things that can be done on
the original PSP that cannot be done at all on this new all
singing all dancing collection of jargonese. I still use the old one.
All Best, Raymond

K urgess
26th January 2008, 18:52
Photopaint has a colour mask facility that I use quite a bit to remove the discoloured paper from behind prints. Unfortunately there isn't enough contrast in your picture to differentiate between the grey of the glass and the drawing in all instances. You get about 50% of the drawing selected.
The same applies to converting it to vector graphics.
Serif Photoplus 7 has a total distortion tool that I hadn't tried before.
The picture is the result of about 5 minutes fiddling.
I usually find you have to use a lot of tricks from different software packages before you get a decent result.


Bob Preston
26th January 2008, 19:30
Have you tried a Polarising Filter !!!!!! Here we are getting overwhelmed with vectors etc.. and forgetting basic optics! What makes it so galling is I have one for my Canon T90 lying 9 the left of my keyboard. So if you have one it will eliminate all reflections. But you will loose about 3 stops.

Who's a smart ****!!


PS my spell checker tells me I've spelt **** wrong. Oh dear

K urgess
26th January 2008, 19:49
Sorry bob but this is about making the best of existing pictures.
As Raymond said he doesn't want to go back and retake so he wants a solution that'll work on what he's got.
I'm sure next time he'll have a polarising filter fitted.[=P]


26th January 2008, 20:41
Yup, I have a few oblique photos of plans, some on walls behind
glass/perspex. The problem is equally about plans on desks, with
poor lighting where I have had to get the best I could in poor circumstances.
I used to use a polarising filter on my old neg film camera, but have not
yet got a "round tuit" for this digital jobby. Most reading search rooms are
not equipped for the digital age, and it is also necessary to accept the
fact that some pictures will have a certain amount of Noise on the image.
In a nutshell, I am glad to get anything in this way. Proper Job !!
Best Wishes, Raymond