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Member
 
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| Hi, Could anyone pls advice some usefull tips to fix a camera for the best view in 3Ds Max. As an example, I put a target camera for my highway viz with camera ht 3m, target ht 2m and focus 50mm (I've told 50mm is the human eye view!). I got the view but the far away buildings looked so close and big and non proportional to the existing situation. Then I dig some old files and found the camera was fixed for 24mm and use target distance set to 300m etc. etc. It seems there must be some formulae (tips) to fix a good camera. Any comments welcome??
Jerlin
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"old dog"
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Über Geek
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There might be a formula out there, but we don’t use it. The best way to get a good match is to use the Camera Metadata to derive your Focal Length. To find this, open Photoshop CS or CS2 and go to File>Browse. This will open the file browser in CS and laceName w:st="on">AdobelaceName> laceType w:st="on">BridgelaceType> in CS2. Navigate to where the image is located and select it. In the left area of the screen, you should see a Metadata tab. In here you can get every bit of information the camera will give. Some higher end cameras will give a lens focal length in 35MM equivalent or the native amount of the camera. A 35MM equivalent is best as it is the Camera MM value in the modifier tab for 3ds max. If the data for focal length is in a native value, you must find out the size of the imager or backplane of the camera. This value is then entered into the Common Properties tab of the Render Control Panel in Max, right next to where you set the render resolution. It’s called Aperture Width. Once this is done, you should be able to get a fairly close camera match in max. If you have measurements from your location, this makes the camera match easier as you can create geometry in your scene that approximates the elements in your shot. Once this is done, you simply plug in the focal length data into your camera and manually adjust until your elements match. Good Luck!
Mark Kauffman
Technical Lead / PA
Project Visualization TEC
Parsons Brinckerhoff, Inc.
Kauffman@pbworld.com
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Junior Member
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I am no expert on the subject, but this what I think I know.  Also my knowledge is limited to digital SLR type cameras.
The sensor in all but the most expensive pro digital cameras are smaller than the area exposed on 35mm film. When using a lens designed for film, the image seen by the lens is cropped by the smaller sensor. This results in a multiplication factor to get a relative 35mm focal length. A good source for these numbers are the camera specs at www.dpreview.com.
http://www.dpreview.com/learn/?/key=focal%20length%20multiplier
So for our camera, a Nikon D100, using a 17-35mm lens, I can use a multiplication factor of 1.5 to get my effective focal length of 25-52mm. HTH,
David
-- David Hinnant
IT Manager
NCDOT Enterprise Visualization
www.ncdot.org/~visualization
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loydering (4/10/2007)
Getting the focal length is the tricky part. Yes! This is what I want to know. Thanks a lot for the tips. But still I've some more doubts, pls.... From the reply of Mark Kauffman, I understand, all these setups are for deriving the parameters from an existing photograph of the area. And again this Camera Metadata (may be, i'm not sure) is available only from some particular photographs?!! If existing site photos or datas are not available what we should do? Is it possible to say, Settings for Interior view.....exterior view....Bird'd eye view etc. etc.?? (Some typical formulae!) Thanks.
Jerlin
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"old dog"
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Member
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| Thanks Loydering. I was surprised to see those "Meta Data" through my Photoshop browser as explained by Mark Kauffman. Great! I tried it with some downloaded pictures too! I didn't get time to try those datas in my camera and run in Max. Let me try it soon and will be back. If anybody got any related comments, welcome anytime!
Jerlin
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Veteran
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The other big thing for camera matching existing photos is:
[size=5] DO NOT CROP THE IMAGE!![/size]
That will make it nearly impossible to ever get an accurate sim. That includes stitched panos. you always want to work with a completely unadulterated source image (save for color correction)
Back to the original intent of the post (as I understood it):
When creating cameras for a 3D rendering or animation, there's no formula for awesome looking images, but there's some things that will make them more realistic and more pleasing to the eyes:
People are very accustomed to how cameras work, even if they've never touched one. We see them every day on TV and the movies and pictures, so we know what to expect. In 3d, you can create very unrealistic cameras and situations. What I've done personally is to try and pay attention to what focal lengths and techniques professional cinematographers use for certain shots/situations.
In your case, the narrow focal length made everything look "flat", but you wanted more depth, so a wider angle lens, and positioning the camera closer to your subject gave you more foreshortening, and more depth.
And, slightly off topic: I prefer not to use target cameras, especially in most animations. Target cameras have 2 sets of keyframes to pay attention to (the camera and target) and it can sometimes get very complicated to do simple things, but that's personal choice as well.
--Tom
THOMAS SHANNON
SENIOR DESIGN VISUALIZATION SPECIALIST
PB Project Visualization
http://www.pbprojectviz.com/
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