Every once in a while (doesn't happen much), I write a more serious
note (see sig). This is one such.
I've collected many questions along my studies and my research, and taken the time to present them here.
Without further adieu.
Is the depth of field measured in meters, or as a percent of the zoom? Translating to; At aperture A
, will there be a difference at the depth of field for different distances? Yet clearer - does the depth of field change when having a constant A
aperture, but moving to / away from the subject (assume continuous lens focus)?
If so, doesn't that render close-subject aperture effect irrelevant?
If not, doesn't the distance to the object have any effect on the depth of field?
What do the ratios 1:1 / 1:3.5 / 1:12.5 (general X:Y
) mean? can X
be greater than Y
Why is a dedicated macro lens needed in the first place? Olympus 570 ultra zoom
's lens does 26mm to 520mm, and still macros down to 1cm
. Why do DSLR lens only start focusing at 30cm-40cm? is this limitation meant to squeeze consumer wallets?
- Constant scene
- Constant zoom
- Aperture A
- Starting distance X
- Ending distance Y
As theory: Is it technologically possible to shoot Z
shots from X
in constant focal gaps, such that at aperture A
they collectively cover the whole focal distance, to synthesize 1 image
, such that any object in the scene between X
is in crystal clear crisp sharpness as if the lens was souly focused on it?
Theoretically, this could create high depth pictures, where any object is perfectly focused at any distance range.
If so, why hasn't this been done?
If not, why?
A polarizer filters light waves from different angles to the lens (as I understand). Imagine a photographer shooting a fish just under water level of some river. Now consider light waves from both the fish, and water surface reflections. Both are bouncing off an object in front of the lens, and traveling in a straight line towards the sensor. To be clear - both are traveling along the same line
towards the lens (same angle to lens), the only difference between them is the origin distance (one from the fish underwater, the other from the water surface).
Now, how does the CPL know to filter the reflections wave from the fish wave if they both income to the lens from the same angle?
Gordon recommends applying exposure compensation manually to images taken with a CPL, since it blocks a portion of the light. Since the camera measures the amount of light before each shot through the lens (TTL), why does this have to be done manually? don't the camera realize its darker now from a simple TTL measurement? does this manual set / unset have to be done, or can I forget this recommendation?
How does the behavior change for linear polarizers, and if they produce wrong measurements for the camera's exposure system - why do they still exist?
Why was white balance created? Specifically: A sensor converts an amount of light to a current using an analog mechanism. This analog current is converted to a digital signal through a per-pixel DAC. At this point we have an image we can apply basic SHARP / SAT / BRI / CON and save it to jpeg as is. Why is white balance needed? isn't the signal incoming from the sensor good so we'd need to play with its hue now?
Seems like all this hue-play has brought is trouble, and semi-orange pictures of people because some WB sensor got things wrong and ruined the picture. What am I missing?
What is Astigmatism
in DSLR lenses? are there any samples of element astigmatism? can this be solved? is this done on purpose in some cases?
What does "X elements in Y groups" mean? what does a "group" do? can any customer really conclude anything about a lens from this data (except weight)? if each element essentially decrease the amount of light, doesn't this mean "the smaller the X the better"?
Whats the difference between a penta-mirror
and a penta-prism
Don't anti shake systems (IS/VR, or sensor-shake) proliferate vignetting?
Why is there a shutter? In days of old, a pre-used film strip would "burn" when exposed to light. Thus it had to have been kept safely closed in a dark chamber. A shutter would be used to to make a controlled exposure, and only the wanted amount of light would "brun" the image to the film.
CCDs and CMOS digital sensors don't "burn".
Why aren't they constantly exposed, and only record data when told to? why must we keep counting shutter actuations? is the shutter a dying dinosaur?
Why does the mirror-box still exist? Why is an OVF still needed? Is the micro-4/3rds movement due to all digicams? What would this do to the world of lens?
Thanks in advance
(feel like I dropped a bomb - gona go rest my fingers now