Tag Archives: shift

Using DSLR lenses on 3D rigs.

Just a quick note on a rather obscure subject. I do a lot of 3D work. Buying pairs of PL mount lenses for my F3’s is beyond my budget right now, so I hire in lenses when I need them. However for my own projects I use DSLR lenses, mainly Nikkors and Tokina’s. One thing that i have discovered is that many of the older manual Nikkors have a tendency to shift the image left and right when you focus. This then miss-aligns the rig. The more modern internal focussing lenses are much, much better in this respect with little or no shift at all. The only problem with the more modern IF lenses is that they often don’t have iris rings (so iris is adjusted with a MTF adapter) and the focus control often has a slipping clutch making repeatable focussing a little harder. So neither is perfect. For 3D applications I think the more modern IF lenses are preferable.

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The relationship between White Balance and the Matrix.

So… you want to change the look of the colour in your pictures but are not sure how to do it. One of the first things that you need to understand is the relationship between white balance and the colour matrix. They are two very different things, with two different jobs. As it’s name applies white balance is designed to ensure that whites with the image are white, even when shooting under lighting of different colour temperatures. When you shoot indoors under tungsten lights (you know, the one the EU have decided you can no longer buy) the light is very orange. When you shoot outside under sunlight the light is very blue. Our eyes adjust for this very well, so we barely notice the difference, but an electronic video camera is very sensitive to these changes. When you point a video camera at a white or grey card and do a manual white balance, what happens is that the camera adjusts the gain of the red, blue and green channels to minimise the amount of colour in areas of white (or grey) so that they do in fact appear white, ie with no colour. So the important thing to remember is that white balance is trying to eliminate colour in whites and greys.

The Matrix however deals purely with saturated parts of the image or areas where there is colour. It works be defining the ratio of how each colour is mixed with it’s complimentary colours. So changing the white balance does not alter the matrix and changing the matrix does not alter the white balance (whites will still be white). What changing the matrix will do is change the hue of the image, so you could make greens look bluer for example or reds more green.

So if you want to make your pictures look warmer (more orange or red) overall, then you would do this by offsetting the white balance, as in a warm picture your whites would appear warmer if they are slightly orange. This could be done electronically by adding an offset to the colour temperature settings or by using a warming card, which is a very slightly blue card. If you want to make the reds richer in your pictures then you would use the matrix as this allows you to make the reds stronger relative to the other colours, while whites stay white.