GENERAL: Basics of Photography
Posted: Fri Nov 11, 2005 6:55 pm
Photography basics for Maxwellians
One of the beauties of Mawell is that it’s basically a simulation of a traditional camera. Though most of 3d artists have some background in real photography, it might be useful to put together some essential notions about how to use the Maxwell camera for those who are not familiar with the manual settings. The purpose of this tutorial is not to teach photography (there are plenty of info about that around the web), but to go through the essential settings for the benefit of Maxwell beginners. This will be continued if there is a demand for it and if I have time.
The basic settings of the Maxwell camera are : Film size, Lens focal length, Focus distance, Aperture settings (value, shape, angle), film sensibility, shutter speed.
For still images without motion blur, all these parameters are normally set in this order.
Film size
In classical photography, a large film or CCD is used to capture more details. It compensate for the imperfection of the lenses (that’s why a high end 4 million pixel large CCD digital SLR will yield better looking pictures than a 8 million pixel compact camera). Of course, this is not the case with Maxwell : if you want detailed pictures, render high resolution. The film size setting in Maxwell is only a matter of depth of field. For a given angle of view, the smaller the film, the more DOF you get (that’s why under standard lighting conditions, everything seems in focus when shooting with compact digital camera, and that’s also why if you shoot in 16 mm, you can survive a less than ideal focus pulling whereas in 35 mm this would lead to certain disaster).
Unless you have a good reason to do otherwise, for instance for compositing, it’s generally ok to stick to the default 24*36 mm film size (135 SLR). You still have plenty of control over the DOF with the other settings.
By the way, a good thing to know about DOF is to consider it’s only dependent on two parameters : magnification (ratio between the size of the object and the size of the film) and aperture. The more important the magnification, the less DOF you get. If you are photographing an elephant, there is a good chance that it will be completely in focus ; this unlikely if your are photographing an ant.
Focal length
The effect of the of the focal length on the picture is linked to the film size. A standard lens has a focal length close to the size of the diagonal of the film. For instance, about 45 mm for a 24*36 film, or 85 mm for a 6*6 camera. Through a standard lens, the perspective is the more natural. The objects are neither closer nor farther than they seem to the naked eye.
The horizontal field of view when using a standard lens to take a 4/3 picture is about 45 degrees. That’s not enough for most interior shoots.
A shorter focal length is a wide angle lens. It gives a wider field of view and at the same time, it exaggerates the perspective. The deformations tend to be quite visible for objects located off axis. As it make all thing look smaller, you get more DOF with short lenses.
A lens longer than standard is a telephoto lens, it has a narrow field of view and squash the perspective. It doesn’t deforms the geometry, but the images tend to lack some depth.
Here are some standard focal length for 24*35 film :
18 or 20 mm : very short lens. Horizontal FOV : 89 or 83 ° for 4/3 image. Useful in really tight situations, but exaggerates the perspective a lot. If you want your 9 square meter room look the size of average gymnasium, that’s the way to go. I would not recommend using this unless you really want a special effect.
24 mm : quite short, FOV 73°. Less extreme than above. About the shortest lens I would care to use for an interior shot without feeling bad. Indeed, I would not go under 28 if I can avoid it (64°).
35 mm : all purpose short lens, with 54° FOV. Add a nice dynamism for exterior and interior shots without altering too much the reality. A favorite for action shots. In real life, I’d choose this lens if I can only have one.
50 mm : standard lens with 44° FOV. True-to-life lens. Useful for that.
80 or 135 mm lens : telephoto lenses with 25 or 15 ° FOV. Useful when you need to squash a little the depth or your picture. The first is often a favorite for the portrait, since it avoid the « big nose small ears » effect you get with shorter lens and at the same time allow for a reduced DOF thus better focusing on the main subject. I would not normally care to use longer lenses with Maxwell, since you have normally no limits as where to place the camera. Now, if you want to reproduce this « paparazzi look » in a picture, go for at least 300 mm (7° FOV).
Diaphragm
Diaphragm is a small mechanical device use to reduce the diameter (or aperture) of the lens. It has two purposes : to control the quantity of light going through the lens and to give some control over the DOF. The aperture is set by specifying a number, or f-stop. This number is the ratio between the diameter of the lens and the aperture of the diaphragm : a 8 f-stop means that inner diameter of the diaphragm is 1/8 the diameter of the lens. In real life lenses, the aperture setting ring is etched with standards numbers corresponding to a 50% reduction of the surface (hence of the quantity of light) between two consecutive numbers. These numbers are : 1 (rarely seen, only, for SLR on one Leica and one Nikon lens, both 50 mm and both ridiculously expensive), 1.4, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Real life lenses won’t normally use smaller aperture, but if you really need it, just multiply a number by square root of 2 to find the next one.
The larger the aperture, the smaller the DOF.
For objects much bigger than film size, you can consider that 1/3 of the DOF is located before the focus point (between camera and focus point), and 2/3 behind. So it’s generally a good idea to set the focus a little farther than the main subject of the picture.
When photographing very small objects, such as object significantly smaller than film size, you tend to get more DOF before the focus point than beyond. Anyway, in this case, the DOF is very small, and you may need to use extremely tight diaphragms such as 32 or more.
The shape of the diaphragm has an influence on the aspect of the focus blur. In particular, out of focus bright spots take the shape of the diaphragm. You can control this with shape and angle settings (broken in beta). Furthermore, the term « Bokeh » is used to describe the quality of the blur, notably its evenness. I’m not sure there is any control over this in Maxwell.
Film sensitivity
Quite self explaining. For still images without motion blur, you can leave the default settings and fine-tune your image interactively in the viewer. In real life, high ISO settings films or CCD tend to be noisier. No idea if it’s the same in Maxwell.
Shutter speed
Simply the time of exposure of the film. It is linked to exposure and motion blur. Control of motion blur could be the subject of a tutorial of its own, but we can keep this for later, especially as motion blur quality is quite poor in beta. So shutter speed should be adjusted to match the aperture settings and give a correct exposure.
HD
One of the beauties of Mawell is that it’s basically a simulation of a traditional camera. Though most of 3d artists have some background in real photography, it might be useful to put together some essential notions about how to use the Maxwell camera for those who are not familiar with the manual settings. The purpose of this tutorial is not to teach photography (there are plenty of info about that around the web), but to go through the essential settings for the benefit of Maxwell beginners. This will be continued if there is a demand for it and if I have time.
The basic settings of the Maxwell camera are : Film size, Lens focal length, Focus distance, Aperture settings (value, shape, angle), film sensibility, shutter speed.
For still images without motion blur, all these parameters are normally set in this order.
Film size
In classical photography, a large film or CCD is used to capture more details. It compensate for the imperfection of the lenses (that’s why a high end 4 million pixel large CCD digital SLR will yield better looking pictures than a 8 million pixel compact camera). Of course, this is not the case with Maxwell : if you want detailed pictures, render high resolution. The film size setting in Maxwell is only a matter of depth of field. For a given angle of view, the smaller the film, the more DOF you get (that’s why under standard lighting conditions, everything seems in focus when shooting with compact digital camera, and that’s also why if you shoot in 16 mm, you can survive a less than ideal focus pulling whereas in 35 mm this would lead to certain disaster).
Unless you have a good reason to do otherwise, for instance for compositing, it’s generally ok to stick to the default 24*36 mm film size (135 SLR). You still have plenty of control over the DOF with the other settings.
By the way, a good thing to know about DOF is to consider it’s only dependent on two parameters : magnification (ratio between the size of the object and the size of the film) and aperture. The more important the magnification, the less DOF you get. If you are photographing an elephant, there is a good chance that it will be completely in focus ; this unlikely if your are photographing an ant.
Focal length
The effect of the of the focal length on the picture is linked to the film size. A standard lens has a focal length close to the size of the diagonal of the film. For instance, about 45 mm for a 24*36 film, or 85 mm for a 6*6 camera. Through a standard lens, the perspective is the more natural. The objects are neither closer nor farther than they seem to the naked eye.
The horizontal field of view when using a standard lens to take a 4/3 picture is about 45 degrees. That’s not enough for most interior shoots.
A shorter focal length is a wide angle lens. It gives a wider field of view and at the same time, it exaggerates the perspective. The deformations tend to be quite visible for objects located off axis. As it make all thing look smaller, you get more DOF with short lenses.
A lens longer than standard is a telephoto lens, it has a narrow field of view and squash the perspective. It doesn’t deforms the geometry, but the images tend to lack some depth.
Here are some standard focal length for 24*35 film :
18 or 20 mm : very short lens. Horizontal FOV : 89 or 83 ° for 4/3 image. Useful in really tight situations, but exaggerates the perspective a lot. If you want your 9 square meter room look the size of average gymnasium, that’s the way to go. I would not recommend using this unless you really want a special effect.
24 mm : quite short, FOV 73°. Less extreme than above. About the shortest lens I would care to use for an interior shot without feeling bad. Indeed, I would not go under 28 if I can avoid it (64°).
35 mm : all purpose short lens, with 54° FOV. Add a nice dynamism for exterior and interior shots without altering too much the reality. A favorite for action shots. In real life, I’d choose this lens if I can only have one.
50 mm : standard lens with 44° FOV. True-to-life lens. Useful for that.
80 or 135 mm lens : telephoto lenses with 25 or 15 ° FOV. Useful when you need to squash a little the depth or your picture. The first is often a favorite for the portrait, since it avoid the « big nose small ears » effect you get with shorter lens and at the same time allow for a reduced DOF thus better focusing on the main subject. I would not normally care to use longer lenses with Maxwell, since you have normally no limits as where to place the camera. Now, if you want to reproduce this « paparazzi look » in a picture, go for at least 300 mm (7° FOV).
Diaphragm
Diaphragm is a small mechanical device use to reduce the diameter (or aperture) of the lens. It has two purposes : to control the quantity of light going through the lens and to give some control over the DOF. The aperture is set by specifying a number, or f-stop. This number is the ratio between the diameter of the lens and the aperture of the diaphragm : a 8 f-stop means that inner diameter of the diaphragm is 1/8 the diameter of the lens. In real life lenses, the aperture setting ring is etched with standards numbers corresponding to a 50% reduction of the surface (hence of the quantity of light) between two consecutive numbers. These numbers are : 1 (rarely seen, only, for SLR on one Leica and one Nikon lens, both 50 mm and both ridiculously expensive), 1.4, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Real life lenses won’t normally use smaller aperture, but if you really need it, just multiply a number by square root of 2 to find the next one.
The larger the aperture, the smaller the DOF.
For objects much bigger than film size, you can consider that 1/3 of the DOF is located before the focus point (between camera and focus point), and 2/3 behind. So it’s generally a good idea to set the focus a little farther than the main subject of the picture.
When photographing very small objects, such as object significantly smaller than film size, you tend to get more DOF before the focus point than beyond. Anyway, in this case, the DOF is very small, and you may need to use extremely tight diaphragms such as 32 or more.
The shape of the diaphragm has an influence on the aspect of the focus blur. In particular, out of focus bright spots take the shape of the diaphragm. You can control this with shape and angle settings (broken in beta). Furthermore, the term « Bokeh » is used to describe the quality of the blur, notably its evenness. I’m not sure there is any control over this in Maxwell.
Film sensitivity
Quite self explaining. For still images without motion blur, you can leave the default settings and fine-tune your image interactively in the viewer. In real life, high ISO settings films or CCD tend to be noisier. No idea if it’s the same in Maxwell.
Shutter speed
Simply the time of exposure of the film. It is linked to exposure and motion blur. Control of motion blur could be the subject of a tutorial of its own, but we can keep this for later, especially as motion blur quality is quite poor in beta. So shutter speed should be adjusted to match the aperture settings and give a correct exposure.
HD
