Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-08-2011, 04:25 AM   #1
New Member




Join Date: Dec 2009
Photos: Gallery
Posts: 13
Exposure time and camera

Do exposure times vary according to camera make? Using my pentax k2000, using f2 lens at f2, I always get exposure time greater than 1 sec for indoor shots with ISO < =200.Even with ISO bumped to 800, I can never go over 1/20. Wonder if the GXR is a great low light performer. Eg:-

Exif | VenusFort | Flickr - Photo Sharing!
Exif | VenusFort | Flickr - Photo Sharing!
Exif | VenusFort | Flickr - Photo Sharing!

So, using the same lens at the same aperture,same light conditions, do exposure time vary for different cameras?

03-08-2011, 05:43 AM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
in principle, ISO 200 is the same on every camera, but there has been some debate on camera makers deliberately mis calibrating things.

for lenses, F2 is a mechanical property of the lens, specifically the focal length divided by the opening diameter . Individual lenses may have different light lossses so exposure can vary from lens type to lens type.

your issue is shooting at IS0 200,. if you can't get exposure at ISO 200 no camera will, you need either to raise the ISO or add external light.

when they talk about low light performance they are talking about the difference in image quality at high ISO from one camera to another.
03-08-2011, 05:47 AM   #3
Veteran Member




Join Date: Nov 2010
Location: Fife, Scotland
Posts: 834
They shouldn't. You do get slight variations between lenses as they transmit slightly different amounts of light but I say again, these are slight variations - for example the same ISO and f-stop in identical conditions might give 1/30th on one setup and 1/25th on another.

You weren't there with your camera when they took the shots, so you don't have a direct comparison. I suspect the location had a lot more light than the average indoor setting.
03-08-2011, 08:34 AM   #4
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,400
QuoteOriginally posted by cats_five Quote
They shouldn't. You do get slight variations between lenses as they transmit slightly different amounts of light but I say again, these are slight variations - for example the same ISO and f-stop in identical conditions might give 1/30th on one setup and 1/25th on another.

You weren't there with your camera when they took the shots, so you don't have a direct comparison. I suspect the location had a lot more light than the average indoor setting.
I have an old rikenon 135F2.8 which begs to differ. it is a full stop slower at any aperture.

there are also many "anicdotal" comments about large differences between DA or similar technology lenses even posted in the forum.

Not saying they are all right/correct in the post, but the issue is often commented or reported on.

At one time, there were lenses calibrated in T stops, this went away not so much because lenses got better (they did but that was coincidence) but because metering, and later flash metering were done through the lens, so knowing the true transmission factor became less important.

to get back to the OP's post, I think the final question is, YES. Same light Same lens, same settings, exposure does change because of what I mentioned earlier, each camera maker "cheats" a little on declared ISO.

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, exif, exposure, exposure time, f2, flickr, iso, pentax help, photo, photography, time
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
how to bracket exposure time? Urmas R. Pentax DSLR Discussion 4 02-01-2010 07:31 AM
Exposure Time fusionimaging Troubleshooting and Beginner Help 6 11-29-2009 01:31 PM
Camera Exposure Compensation with Flash With camera in Manual Mode jrforman Flashes, Lighting, and Studio 0 09-11-2009 10:03 AM
Long time exposure must use NR? yipchunyu Pentax DSLR Discussion 21 06-21-2009 05:08 PM
Trouble with Exposure Time jcleary47 Photographic Technique 7 06-17-2008 04:24 AM



All times are GMT -7. The time now is 03:54 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top