perspective match

[e[dub]]

Anyone have any tips to successfully match a view to a photograph?

 

Is there anything in the manual about this? (if so, I can't find it).

 

What if I don't know the focal length of the camera used to take the picture? On most digi cameras the focal length changes w/ zooming anyways, right?

 

Is it just trial and error with moving camera around?

 

Do you use the editor camera, or a view camera?

 

Any suggestions welcome.

 

-Erik

[leed]

have a look at this

http://www.vreel-3d.de/plugins/PhotoMatch/links.html

produced by

Arndt von Koenigsmarck

 

hope it helps

[ecastillor]

What i do,when i take the photo is put markers of the corners of the buildings real dimmensions with stones or little flags or whatever, , and try to find a phisical reference within the picture for height.

 

Then I draw guides in PS over my picture and use this as a pre background. Use the horizon as a guide also,and when my camera is ready i replace my background with tho original picture and presto! Render as TGA to get an alpha channel

 

(I usually tweak the render a little in PS to perfectly match the background)

[e[dub]]

have a look at this

http://www.vreel-3d.de/plugins/PhotoMatch/links.html

produced by

Arndt von Koenigsmarck

 

hope it helps

 

looks nice! have you tried it?

[STRAT]

i've usually a good idea where the photo was taken compaired to where i place the camera in my model, but yup, it's usually an eye things up job. that works nicely with the more experience you get.

 

also, try mapping everything with frontal mapping of the backround photo when judging the camera, this will also help slip things into place better.

[Chris_Mac]

']

What if I don't know the focal length of the camera used to take the picture? On most digi cameras the focal length changes w/ zooming anyways, right?

 

 

 

-Erik

 

If your photo has been taken on a digital camera, then the focal length of the shot will be stored in the EXIF data.

 

To access this info, open your image in photoshop and acces it via File >> File info - then under "section" select EXIF.

 

You can also find the make and model of the camera which took the photo - this is useful in finding the aperture width of your camera. I use this website quite a lot... it has the technical specs of most available digital cameras:

 

http://www.dpreview.com

 

Once you have the focal length and the aperture width of your photo, you can then input this data into your camera in Cinema, which should make it much easier to match the shot.

 

Hope this makes sense.

 

[e[dub]]

 

To access this info, open your image in photoshop and acces it via File >> File info - then under "section" select EXIF.

 

I just had my mind blown!... this is VERY useful!! Thanks

[leed]

Sorry e[dub]

been away from my computer for a while.

 

I have used the pers match tool...

I think it is ok if you have good references in the image, definite paralell lines running off to the left and right.

lee

[Wokka]

The information from EXIF is great, but how does it relate to the C4D camera. My image in Photoshop says the Focal Length is 9.3mm or 93/10, what settings should I place in the camera object for Focal length (93?), apature width and field of view? I've tried photomatch on the same image and it tells me the focal length should be 41(ish).

I've also tried 11th Moons cameramatchsystem but it's documentation is difficult and again I don't get consistant results.

I'm so confused, I think I need a lie down.

 

Any help asap would be really appreciated.

 

Cheers

[Chris_Mac]

Okay,

 

first off you need to know the aperture width of your camera.

 

You can usually find it at this website = http://www.dpreview.com....

 

For example, if your camera is a Canon Powershot G6, you would find it's tech specs here - http://www.dpreview.com/reviews/specs/Canon/canon_g6.asp

 

We can see that it's sensor size is 7.18 x 5.32 mm... (see attached image)...

 

In the camera settings in Cinema, your aperture width would be 7.18 (for landscape photographs) or 5.32 ( for portrait photographs). Your focal length would be the focal length from the j-pegs EXIF data.

 

These settings should produce the field of view angle to match with your photograph.

[Jorge Arango]

Okay,

 

first off you need to know the aperture width of your camera.

 

You can usually find it at this website = http://www.dpreview.com....

 

For example, if your camera is a Canon Powershot G6, you would find it's tech specs here - http://www.dpreview.com/reviews/specs/Canon/canon_g6.asp

 

We can see that it's sensor size is 7.18 x 5.32 mm... (see attached image)...

 

In the camera settings in Cinema, your aperture width would be 7.18 (for landscape photographs) or 5.32 ( for portrait photographs). Your focal length would be the focal length from the j-pegs EXIF data.

 

These settings should produce the field of view angle to match with your photograph.

 

By the way, the words "aperture width" seem misleading to me since aperture in photography relates to f stop. Should be something like "back plane width" or similar.

 

Jorge Arango

[Wokka]

Chris_Mac, thanks for that clarification.

So (assuming my camara's senso size is 7.18), focal length is 9.3,Apeature Width is 7.18 and therefore field of view is 42.215! Great. Time to test it in the real world

 

Jorge, couldn't agree more. I've been a amatuer photographer for years (ahh the smell of developing fluid in a red lite room brings tears to my eyes). Maybe thats why I get so confused.

 

Thanks guys

[Ernest Burden III]

(ahh the smell of developing fluid in a red lite room brings tears to my eyes)

 

All day, all night. Then you emerege with one really nice print.

[edub]

Okay,

 

first off you need to know the aperture width of your camera.

 

You can usually find it at this website = http://www.dpreview.com....

 

For example, if your camera is a Canon Powershot G6, you would find it's tech specs here - http://www.dpreview.com/reviews/specs/Canon/canon_g6.asp

 

We can see that it's sensor size is 7.18 x 5.32 mm... (see attached image)...

 

In the camera settings in Cinema, your aperture width would be 7.18 (for landscape photographs) or 5.32 ( for portrait photographs). Your focal length would be the focal length from the j-pegs EXIF data.

 

These settings should produce the field of view angle to match with your photograph.

 

 

It's been a while since I started this thread, but I guess I always eye-ball a good enough view, and forget about my struggles with this... until the next project!!!

 

Now, I re-read the step-by-step above, and it all started to make sense - but I still don't get a good match!!

 

It seems I don't have enough of a wide-angle, based on the above method. Does everyone else get good results??... is it just me??

 

p.s. I realize I need that Photmatch plug-in!!

[Wokka]

Erik,

Don't expect too much from the plug-in. I've been using it for a while and though helpfull I still don't feel it is the 'be all and end all' for photomontage matching, espescially with wide angle camera angles. The camera match system is a bit more logical in it's use but doesn't always create a result.

 

My usuall workflow is to take the photo, build a model of existing buildings from a survey and then try the camera match system or photomatch plugin to place the camera in the correct position. The Photomatch plugin doesn't put the camera into an existing model but just creates the correct camera for the job (approxiamatley). You then create a polygon trying to match the correct height and length. I then take the camera and polygon (together under a null) into the building model and rotate, scale and move the null untill the polygon match's an equivilent building in the survey model. This sounds like it should work, but either through my poor modelling or judgement, it hasn't ever been that easy and I still spend hours (literally) trying to get a good match. Don't get me wrong, I think it is a good plugin for what it does, but the actual mechanism of lining up arrows on a screen isn't ever going to be 100% correct so I guess I feel there needs to be a different approach that uses real vectors and lines.

I'm a bit paranoid about this as I've almost been caught out with a minor difference (500mm) and could have cost my clients a lot of money. No amount of disclaimers was going to satisfy them. Unfortunatley this is becoming a really critical part of my work and as councils, commitee's and clients now expect anything that comes from a computer to be extremely accurate, relying on moving a few lines on a digital image to create a camera that 'looks right' but may not be could cost me a day in court.

Anyhow, midnight on a Saturday night and I think I need some sleep. Good luck and let me know if you find the 'click this button to place camera' plugin that is accurate.