Go Back   Steve's Digicams Forums >

Reply
 
LinkBack Thread Tools Search this Thread
Old May 20, 2019, 8:34 AM   #1
Senior Member
 
Join Date: Jan 2013
Posts: 362
Default Iris vs ND filter

Hi,
I've heard that many of the modern cameras have replaced the iris with ND filters. Can anyone confirm this? If this is so, can anyone explain how ND filters would perform the same function as an iris?
Thanks,
.... john
Shinnen is offline   Reply With Quote
Sponsored Links
Old May 20, 2019, 2:19 PM   #2
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,723
Default

It's true of many 'Point & Shoot' cameras, because it's simpler and cheaper than a mechanical iris.

Either is used to limit the amount of light that gets to the sensor. An iris does it by making the hole smaller. An ND filter does it by absorbing and reflecting some of the light. The effect on exposure is the same, but while using an iris changes the Depth of Field, using an ND filter does not. That's why it's not often used in more expensive cameras where their owners often want to adjust the depth of field.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old May 20, 2019, 5:25 PM   #3
Senior Member
 
Join Date: Jan 2011
Location: Australia, New South Wales central coast
Posts: 3,301
Default

G'day John

You will have seen many a camera lens with the diaphragm opened / closed to form the apertures... and while this works well on lenses over say, 50mm - when it comes to shorter focal length lenses, the physical sizes of everything becomes so much smaller

Now think of a fone-camera and the 'how-to' moderate exposure when dealing with such tiny, tiny lenses

Variable ND filters are also often used in video cameras, as their frame rate / shutter speeds would give exposure issues on very bright days - so they often have an ND filter that drops exposure by either 2-stops or 4-stops just to make things a bit easier

Hope this helps, Phil
__________________
Has Lumix mirrorless & superzoom cameras and loves their amazing capabilities
Spends 8-9 months each year travelling Australia
Recent images at http://www.flickr.com/photos/ozzie_traveller/sets/
Ozzie_Traveller is offline   Reply With Quote
Old May 20, 2019, 10:47 PM   #4
Senior Member
 
Join Date: Jan 2013
Posts: 362
Default

So, if the camera gives a range of apertures, (i.e. 10) from large to small then I'm safe in assuming that it has an iris?
...... john
Shinnen is offline   Reply With Quote
Old May 21, 2019, 3:18 AM   #5
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,723
Default

Yes. Cameras that use ND filters, usually only have one or two filters for adjusting exposure.
__________________
  • The lens is the thing.
  • 'Full Frame' is the new 'Medium Format'.
  • "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
TCav is offline   Reply With Quote
Old May 21, 2019, 6:26 PM   #6
Senior Member
 
Join Date: Jan 2013
Posts: 362
Default

Thanks again guys.
.... john
Shinnen is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 3:03 PM.