Hello,
I’m trying to do some motion tracking with blender.
To have good results, we need to precise the focal used by the video camera, and the CCD width.
But I have difficulties to understand the constructor language.
My video camera is a sony DCR-SR58E.
The specifications (http://www.sony.fr/support/fr/product/DCR-SR58E/specifications) tells me the CCD is 2.3cm, but is it the width?
Infact, I’m lost between 1.8 focal (wich is very small, isn’t is?) and the relation with CCD, and the 35mm equivalence.
Wll, I’m confused, so does anyone can help me to give blender the correct parameters please?
Thank you
ps : sorry for my bad english, I’m french.
The image sensor is 1/8" which gives a sensor width of 1.6mm http://en.wikipedia.org/wiki/Image_sensor_format
For the focal length only you know what you used when you shot the footage (1.8 to 108mm)
Thank you for your answer.
Unfortunately, I have an error of around 2000, compared to 12 as vith the default parameter. So I guess these parameters should not be correct.
Thank you for your answer.
But i fear that these values aren’t good, because the error factor is over 2000 with them, and around 12 with default parameters…
I still have a big error factor in blender (~120) with these parameters. I don’t understand where could be my mistake, because There is no other values given by sony.
quoted in agreement… 1.8 would only be the right value if you were shooting at 1x(see below)… did you shoot at 1x?
Speaking of zoom, if you zoom in or out during the clip, I don’t think it’s possible to track it.
Yes, you can use the 35mm equivalents, and in my opinion it might actually be better. The tables from the link above show typical sensor sizes and can vary by manufacturer (it shows a 1/8 sensor diagonal of 2.0 and yours is clearly 2.3). If they give you the equivalent values, they have already taken all of this into account.
From your link:
Image Device: Size 2.3cm (1/8 type) CCD Sensor
F1.8-6
f (Focal Distance) (mm)1.8-108
f (35mm conversion): Camera mode (mm)16:9 Mode . 39-2340/ 4:3 Mode . 44-2640
f (35mm conversion): Memory mode (mm)16:9 Mode . 49-2944 / 4:3 Mode . 44-2640
It shows you that even though 1.8 seems to be very small, it translates to 49 (in 16:9,memory mode) which is pretty standard.
The specs above also bring up another interesting fact… the effective sensor width can change according to the mode that you are in…That is how you can end up with 3 different focal length ranges with the same lens. That means when you shoot your video you not only have to document what level of zoom* you are using but what mode(s) you are in (ie: a wide shot in memory mode 16:9 is 49 & in 4:3 it’s 44)
Note: zoom level is often what a camera like this shows you and it is just a multiplication of your base focal length
(49 - 2944 indicates you have a 60x zoom capability 2944/49=60)
so if you are shooting at exactly 5x your focal length would be 495=245
To make a long story short, leave the width at 35, determine your base focal length by the mode you are in(39, 44,or 49), and multiply that by zoom to get your focal length
Finally, turn off image stabilization, it can mess up your distortion values and your solve