- What is Angle of View?
- What is an Achromat Diopter?
- How is an Achromat different
from a standard close up lens?
- What is a matte box?
- What is a lens shade?
- When do you need a lens shade
or a matte box?
- What is aspect ratio?
- What is 4:3?
- What is 16:9?
- What is anamorphic video?
- What is the difference between
the Mark I and Mark II fisheye lenses?
- What is anti-reflection coating?
- How should I clean my lens?
- Why should I use a bayonet
- How much does my accessory
- What is hyperfocal distance?
- What is the Hyperfocal distance
of my lens?
- What is a T-Stop?
- What is a PL mount?
1. What is
Angle of View?
Angle of view is a measure of how much of the
scene a lens can view. A fisheye lens can see
as much as 180 degrees and a telephoto lens might
see as narrow an angle as 5 degrees. It is important
to distinguish horizontal angle of view from
the vertical angle of view.
2. What is an
An achromat diopter is a highly corrected two
element close up lens that provides extremely
sharp images edge to edge without prismatic color
3. How is an
Achromat different from a standard close up lens?
Standard close-up lenses, or diopters,
are single element lenses that allow the camera
lens to focus more closely on small objects.
Single element diopters accomplish this, although
the image may not be uniformly sharp from edge
to edge and some color fringing may be visible.
What is a matte box?
A matte box is a professional light
control system, offering lens shade functions,
filter holders (usually rotatable) and accessories
such as French Flags, side flages and eyebrows.
5. What is a
A simple device that shades the lens
from stray light, improving contrast and reducing
internal reflections and lens flare. A sophisticated
lens shade may have a simple provision for
mounting a filter.
6. When do you
need a lens shade or a matte box?
To minimize stray light hitting or
entering the lens. Properly shading the lens
can increase contrast and image quality.
7. What is aspect
The ratio of width to height of an
image. This is a commonly used method of identifying
different video formats.
8. What is 4:3?
This is the aspect ratio of standard
broadcast television worldwide. Pronounced
as: “four by three”.
9. What is
This is a widescreen video format aspect ratio.
HD video is 16:9. Pronounced as “sixteen
10. What is
This is a process to capture 16:9
widescreen video using a standard 4:3 camera.
The video is captured using a cylindrical anamorphic
lens to squeeze the image and the resulting
imagery is unsqueezed during post production.
11. What is
the difference between the Mark I and Mark II
The MKI fisheye was designed for cameras
such as the Sony VX1000 Mini DV camera. Many
professional users objected to the amount of
vignetting present in the MKI Ultra Fisheye.
The MKII fisheye was designed for newer cameras
such as Sony VX2000/PD150 and the Canon GL1/2,
which have larger lenses, requiring a larger
fisheye. Vignetting was eliminated in the Mark
12. What is
Thin film anti-reflection coatings
greatly reduce the light loss due to reflection
in multi-element lenses. Reducing these reflections
results in a dramatic reduction of lens flare
and increased contrast.
13. How should
I clean my lens?
See our lens
14. Why should
I use a bayonet Mount?
Most DV cameras have lenses that use
plastic parts, including the accessory thread
on many lenses. Mounting and unmounting an
accessory lens many times can result in damage
to those threads. By utilizing the bayonet
on the front of the camera that was originally
intended by the manufacturer to secure the
lens shade, accessory lenses can be mounted
more quickly and reliably, without damaging
your camera lens.
15. How much
does my accessory lens weigh?
See the Specification
What is hyperfocal distance?
Depth of field is the zone of acceptable
focus in front of and behind the point of best
focus. If a lens is focused at infinity, the
depth of field beyond the focus point (beyond
infinity) is wasted. For a particular lens,
aperture and film format size, the depth of
field can be maximized by focusing the lens
at the hyperfocal distance. The hyperfocal
distance is the point of focus chosen so that
the depth of field extends from a near point
to infinity. As you stop down the lens, the
depth of field increases and therefore the
hyperfocal distance is closer to the camera.
What is the Hyperfocal distance of my lens?
That depends on the lens focal length,
film format size and lens aperture you are using.
You can use our Depth of Field Calculator spreadsheet
(requires Excel) to calculate hyperfocal distance
for your various requirements.
What is a T-Stop?
A T-Stop is just an f-stop adjusted for light Transmission (T for Transmission).
Transmission is affected by both absorption and reflection within a lens.
It won't matter as much on a short camera lens for photography, especially if you're metering through the lens.
In cinematography, especially in the film days, they NEVER metered through the lens.
That's changing now with digital cameras, where you can see images on a monitor and see the exposure on a scope.
In any case, the problem in the film days was that a short prime lens marked f2.8 or a LONG zoom lens marked f2.8, would give radically different exposure because there's a LOT more glass in that long zoom lens.That glass absorbs light and each element reflects light, especially when there's an air gap. So meter with your incident light meter, shoot with a short lens, every-thing's fine.
Put the big long lens on the camera and suddenly the negative is nearly a stop under exposed. Bad for your career as a camera operator.
So to correct this, lenses were marked in T-stops (T for transmission), to compensate for lenses with more glass, better or worse AR coating, etc..
See an explanation of the T-Stop/F-Stop relationship here:
What is a PL mount?
The PL Mount is arguably the standard lens mount for cinematography today. Compared to standard DSLR mounts, the PL Mount is a very robust and solid mount.
It's absolutely rock solid and can hold a very long lens without any movement or vibration.