Camera match - digital SLR

[moshenko]

Hi,

 

I must be going crazy, and I haven't done a decent camera match project in a while, but I'm having a horrible time getting a Max camera to match the view of a photo and I'm not sure why. Without going into a lot of detail about the project (I can't) is it unreasonable to expect that a base photograph taken with a full-frame digital camera (Canon EOS 5D) and a 50mm lens should be able to be accurately matched using a Max 50mm camera? For the life of me I can't get it to work out. I've dealt with other matching projects where a crop factor had to be taken into consideration because the source photo was taken with a non-full-frame digital camera but I thought this one would be different.

 

Does anyone have some advice/thoughts on this?

[thatch]

Im no lens expert but isnt the 50mm on that camera the 35mm equivelant and you should be using the actual values?

[moshenko]

Im no lens expert but isnt the 50mm on that camera the 35mm equivelant and you should be using the actual values?

 

That is my understanding, and that's what I'm trying to do but it just ain't workin'. What does work is using a Max 80mm camera (which would be roughly the crop-factor equivalent if this camera was not full-frame). Clearly, I must be messing something up somewhere, although it's kind of hard to do so in this situation

[William Alexander]

Did you take the lense distortion out of the Base image? Have had some major problems with lense distortion and camera matching...in any app. Some work without being corrected, others....will give you fits for an eternity unless the base image is corrected.

 

 

My 10cents

Wax

[nisus]

digital camera (Canon EOS 5D) and a 50mm lens should be able to be accurately matched using a Max 50mm camera

 

Not at all! Check camera-info online... as far as I remember there is a factor 1.23 (or so) that makes up for the difference between digital and analogue camera.

Call your dealer, he should know.

 

rgds,

 

nisus

[sterealkey]

Guys does Max not automatically adjust your camera lense in a case like this?

 

Ive done many camera matches and never have a problem like this, it matches perfect everytime.

 

Are you trying to match it by eye, or are you using Max's camera match tools?

 

The only other thing I can think of is maybe an incorrect measurement on your model somewhere, like maybe something in your model is longer or shorter than it is on site.

 

I'll be watching this thread. Peace

[nisus]

Guys does Max not automatically adjust your camera lense in a case like this?

 

Not if you use the 'freeze FOV' in the camera match tool... because the 50mm virtual camera is NOT the same as the 50mm of your SLR...

 

nisus

[moshenko]

Not at all! Check camera-info online... as far as I remember there is a factor 1.23 (or so) that makes up for the difference between digital and analogue camera.

Call your dealer, he should know.

 

rgds,

 

nisus

 

This is true for some cameras (most DSLR's have a "crop factor" of about 1.6), but not the 5D. It is indeed a full-frame DSLR with no crop factor. In other words (and according to a photographer friend of mine) an image shot with the same lens on both a Canon 5D and a film SLR should be identical in terms of the extent of image that is captured.

[moshenko]

Hi,

 

Last night I figured out what my issue was, and the answer was so simple I wanted to smack myself: I had shot my pictures in portrait orientation because the subject (new building) is a tall-ish tower. In Max I set up my camera to match the real lens (50mm) and set my render size to equal that of my photo which, in my case, was 2912px wide by 4368px tall (12 megapixel camera!). This was my big mistake, and the answer lies in the fact that all lenses have different vertical and horizontal fields of view (FOV). In the real photo, I actually turned the camera on its side to gain a portrait orientation. This meant that the horizontal FOV was now the vertical FOV, and vice versa. However, in Max all I did was change the size of the render while maintaining the same FOV values (as set by the lens size). The result was a horizontal FOV that was much too wide and a vertical FOV that was much too narrow, causing the match to be completely wrong. Now that I’ve gone through the exercise the answer is simple (in the case of my 50mm lens):

1. Calculate the FOV for the real world lens (http://www.tawbaware.com/maxlyons/calc.htm has a nice FOV calculator);
   
2. Adjust the horizontal FOV and vertical FOV values of the Max camera to match the vertical FOV and horizontal FOV (respectively) of the real world lens. This is because the physical camera was rotated and the FOV numbers are now reversed;
   
3. Perform the camera match with the new camera which now reads as being a 74.975mm lens.

I tested this by setting up a scene and comparing the rendering results (see attachment). You can see that the three images produce a box of the same size (when the camera is in the exact same spot each time), but the image where the render size is simply adjusted to match the portrait photo size the subject is much smaller, indicating an incorrect FOV. I suppose this would have been most obvious if I had been using the “35mm” setting from the Output Size dropdown; it would have forced me to realize that I needed to either change the orientation of the camera or adjust the camera FOV values.

 

I can't believe that this is something that I have never really concentrated on; it's kind of embarassing to learn this after doing this kind of work for so long!

[William Alexander]

LOL......The devil is in the detials, isn't it. Cough, I've never made an error like that EVER before,

 

Not sure, but I don't believe I ever saw that Max ever got enough information to actually "correct" for lens distortion. If the building you're matching goes from center frame off to one of the corners.....you can get a match in max, however if your using the image and camera mapping or modeling from it....You'll know, you'll know The edges of the projected image are curved and the mesh is not. My thoughts

 

Wax