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− | Many small form factor cameras such as the IXUS/SD series only have one real aperture setting, which is commonly f/2.8 at wide-angle ( |
+ | Many small form factor cameras such as the IXUS/SD series only have one real aperture setting, which is commonly f/2.8 at wide-angle (i.e. when the camera is not zoomed in at all). |
− | The lens in all point |
+ | The lens in all point-and-shoot cameras (and some D/SLR zoom lenses) has a variable maximum aperture value (lowest f number), which means Canon will list the camera with zoom specs 6.2 - 18.6mm and aperture f/2.8 - 4.9. |
− | In this case, the maximum aperture will be f/2.8 when the camera is at its |
+ | In this case, the maximum aperture will be f/2.8 when the camera is at its widest focal length (6.2mm) and increases as you zoom in until the telephoto setting (of 18.6mm) is reached with an f-stop maximum value of f/4.9. That is, when zoomed in at 18.6mm the camera is at f/4.9 and cannot go any lower (i.e. to f/2.8). |
− | + | This is why there are different aperture values when zooming in, despite these cameras having a single fixed aperture. |
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== How the ND filter in these cameras work == |
== How the ND filter in these cameras work == |
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− | When your camera detects a really bright scene, it |
+ | When your camera detects a really bright scene, it will swing the ND filter in. This in effect makes the scene look darker and will effect the exposure (but not depth of field as a real aperture would). |
− | With the ND filter in, the camera can select a slower shutter speed without |
+ | With the ND filter in, the camera can select a slower shutter speed without overexposing the entire scene. |
Also, with the ND filter swung in, the camera will capture an image with an aperture of f/8 - This is a fake aperture value caused by the ND filter swinging in. |
Also, with the ND filter swung in, the camera will capture an image with an aperture of f/8 - This is a fake aperture value caused by the ND filter swinging in. |
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− | With CHDK |
+ | With CHDK the ND filter out can be kept out, but a faster shutter speed to compensate as to be selected. |
− | In CHDK |
+ | In the CHDK menu this operation can be found at: |
Extra Photo Operations -> ND filter state |
Extra Photo Operations -> ND filter state |
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'''Notes:''' |
'''Notes:''' |
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− | * |
+ | * Setting the ND position in a script takes effect just before the actual shot is taken and after the exposure is set; |
* Not all cameras have an ND filter; all cameras of the Ixus series have a ND Filter instead of a real aperture, also some other ones, e.g. the A450, A460, A530, A550, A560, A1000, TX1. |
* Not all cameras have an ND filter; all cameras of the Ixus series have a ND Filter instead of a real aperture, also some other ones, e.g. the A450, A460, A530, A550, A560, A1000, TX1. |
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* Some higher end cameras have both an ND filter and a real aperture, e.g the cameras of the G series. |
* Some higher end cameras have both an ND filter and a real aperture, e.g the cameras of the G series. |
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== External Resources == |
== External Resources == |
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− | * Learn more about Neutral |
+ | * Learn more about Neutral Density filters - http://en.wikipedia.org/wiki/ND_filter |
* Learn more about Minimum/Maximum Apertures - http://en.wikipedia.org/wiki/Aperture#Maximum_and_minimum_apertures |
* Learn more about Minimum/Maximum Apertures - http://en.wikipedia.org/wiki/Aperture#Maximum_and_minimum_apertures |
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* Understanding Camera Lenses - http://www.cambridgeincolour.com/tutorials/camera-lenses.htm |
* Understanding Camera Lenses - http://www.cambridgeincolour.com/tutorials/camera-lenses.htm |
Revision as of 19:30, 29 December 2014
Many small form factor cameras such as the IXUS/SD series only have one real aperture setting, which is commonly f/2.8 at wide-angle (i.e. when the camera is not zoomed in at all).
The lens in all point-and-shoot cameras (and some D/SLR zoom lenses) has a variable maximum aperture value (lowest f number), which means Canon will list the camera with zoom specs 6.2 - 18.6mm and aperture f/2.8 - 4.9. In this case, the maximum aperture will be f/2.8 when the camera is at its widest focal length (6.2mm) and increases as you zoom in until the telephoto setting (of 18.6mm) is reached with an f-stop maximum value of f/4.9. That is, when zoomed in at 18.6mm the camera is at f/4.9 and cannot go any lower (i.e. to f/2.8).
This is why there are different aperture values when zooming in, despite these cameras having a single fixed aperture.
How the ND filter in these cameras work
When your camera detects a really bright scene, it will swing the ND filter in. This in effect makes the scene look darker and will effect the exposure (but not depth of field as a real aperture would).
With the ND filter in, the camera can select a slower shutter speed without overexposing the entire scene. Also, with the ND filter swung in, the camera will capture an image with an aperture of f/8 - This is a fake aperture value caused by the ND filter swinging in.
With CHDK the ND filter out can be kept out, but a faster shutter speed to compensate as to be selected. In the CHDK menu this operation can be found at:
Extra Photo Operations -> ND filter state
Just select one of the options from there: Off/In/Out
- 'Off' means the camera is in control of the ND filter state.
- 'In' means the ND filter is swung in.
- 'Out' means the ND filter is not in.
Notes:
- Setting the ND position in a script takes effect just before the actual shot is taken and after the exposure is set;
- Not all cameras have an ND filter; all cameras of the Ixus series have a ND Filter instead of a real aperture, also some other ones, e.g. the A450, A460, A530, A550, A560, A1000, TX1.
- Some higher end cameras have both an ND filter and a real aperture, e.g the cameras of the G series.
ND Filter Scripting Functions
get_nd_present() - return status indicates whether camera has an ND filter and/or a diaphragm
set_nd_filter() - 0=auto, 1=in, 2=out
An exampe HDR script using the ND filter : http://chdk.wikia.com/wiki/ND_Filter_HDR_Script
List of cameras with ND filter
Camera model | Notes, reference |
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A series | A410*, A420*, A430, A450, A460*, A470*, A480*, A490*, A495*, A530, A550*, A560*, A580*, A710, A800*, A810*, A1000*, A1100*, A1200, A1300, A2000, A2100*, A2200*, A2300*, A3000*, A3100*, A3200*, A3300*, A3400 |
D series | D10* |
G series | G7*, G9*, G10*, G11*, G12*, G1X* |
Ixus series | The cameras in the Ixus line-up lack a physical aperture and use an ND filter instead. |
SD series | See also: Ixus. Look up equivalent model in P-ID (Table) |
SX series | SX40 HS*, SX50 HS*, SX220 HS*, S230 HS*, SX240 HS, SX260 HS |
TX series | TX1* |
(* Per platform/(model)/platform_camera.h - CAM_HAS_ND_FILTER)
Resources
A disassembled IXUS800 (SD700) with photos of lens and ND Filter - http://chdk.setepontos.com/index.php/topic,548.0.html
External Resources
- Learn more about Neutral Density filters - http://en.wikipedia.org/wiki/ND_filter
- Learn more about Minimum/Maximum Apertures - http://en.wikipedia.org/wiki/Aperture#Maximum_and_minimum_apertures
- Understanding Camera Lenses - http://www.cambridgeincolour.com/tutorials/camera-lenses.htm