Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Reply
 
Thread Tools Search this Thread
Old Mar 4, 2010, 9:27 PM   #1
Senior Member
 
Join Date: Jan 2007
Location: Decatur, GA
Posts: 2,053
Default Exposure Issue Help Needed

Today I was playing around with my camera 9Sony A-350) trying to capture longer exposures of water/white caps on a lake. When I set the image to 1.3 seconds or longer all I get a frame that is very very bright - overblown and almost white in nature. If it matters I was also using a tripod and lens hood......

I tried adjusting my f-stops, exposure comp down etc.

What am I doing wrong? What can I do to resolve the issue if anything?

dave
Photo 5 is offline   Reply With Quote
Sponsored Links
Old Mar 4, 2010, 9:41 PM   #2
Senior Member
 
Hawgwild's Avatar
 
Join Date: Mar 2006
Location: Pensacola, Florida
Posts: 3,525
Default

Hi Dave, from the sound of it, you may have more light than the camera can compensate for at 1.3 seconds. In other words, if the scene called for iso 100, f22 at 1/30th sec for proper exposure, then 1.3 sec will blow it out big time. A neutral density filter may be needed for daytime exposures of that length.

Robert
__________________
Always use tasteful words - you may have to eat them.
You cannot find knowledge by rearranging your ignorance.

My Flickr
-Robert-


Hawgwild is offline   Reply With Quote
Old Mar 5, 2010, 5:21 AM   #3
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

I agree. This is the real 'Rule of Reciprocity' in photography. If you double the exposure time, you must halve the ISO or close the aperture a full f-stop. It sounds like you didn't reciprocate for the longer shutter speed by closing down the aperture.
__________________
  • 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 Mar 5, 2010, 8:15 AM   #4
Senior Member
 
Join Date: Jan 2007
Location: Decatur, GA
Posts: 2,053
Default

even at ISO 100 and f/22 it didn't help at all.........

dave
Photo 5 is offline   Reply With Quote
Old Mar 5, 2010, 8:27 AM   #5
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

Then a 1.3 second exposure was just too long. Try something shorter.
__________________
  • 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 Mar 5, 2010, 8:35 AM   #6
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Dave:

The old "Sunny 16" rule of thumb is that an exposure at ISO 100 and f/16 should be 1/100 second. In other words, in brighter lighting, you use the reciprocal of the ISO speed to determine shutter speed at f/16. f/22 is only one stop dimmer than f/16, meaning you'd still need a 1/50 second shutter speed for proper exposure in brighter outdoor lighting. ;-)

If you try to use a shutter speed that's too slow for the aperture, ISO speed and lighting, you'll get an overexposed (too bright image). Likewise, if you try to use a shutter speed that's too fast for the aperture, lighting and ISO speed, you'll get an underexposed (too dark) image.

If you want to try and use shutter speeds that slow in daylight (approx. 1 second), you'll need to reduce the amount of light getting through to the sensor. In other words, using a Neutral Density Filter is your best bet.

For example, something like this 62mm (which is what most Tamron 28-300mm lenses use, but check your lens to make sure of it's filter thread size) ND 1.8 filter would reduce light by 6 stops.

http://www.bhphotovideo.com/c/produc...l_Density.html
JimC is offline   Reply With Quote
Old Mar 5, 2010, 9:16 AM   #7
Senior Member
 
TCav's Avatar
 
Join Date: Sep 2005
Location: Washington, DC, Metro Area, Maryland
Posts: 13,544
Default

It sounds like, if you want to get long exposures in daylight, you need a neutral density filter like Hawgwild suggested.
__________________
  • 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
 
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 Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 12:32 PM.