Pondria
Offline
Dedicated FM
Upload & Sell: Off
|
 p.1 #1 · Dynamic Range Measure | |
It's been more than 6 months since we updated teh FM DR database. We need contributions from the new camera owners.
The procedure I'm proposing is simple and easy. Constructive comments are Welcome. The essence of the procedure is to measure the upper and lower exposure limits of the camera with common s/w that most of us have.
1. Find a off-white color wall. Just make sure that the area has no feature or shadows. Naturally lighted In-door is preferred.
2. Set the Camera ISO @100 ( or whatever the Native ISO )
3. Set the Exposure stop increment to 1/3.
4. Set the Camera at the manual setting. Fix the Aperture @ f/8 or so ( Not critical ). Now, we are going to play with only the shutter speeds.
( If you take more than 2 min through this point, you would not be a photographer  )
5. Click the shutter speed dial to push up your exposure meter to +2.
6. Take a shot, and increment the shutter speed dial by one click.
7. Repeat the step 6 above about 6 times to cover +2 to +4 range with 1/3 increment.
8. Click the shutter speed dial to opposite direction to push down your exposure to -2.
9. Take a shot, and decrement the speed dial by one click.
10. Repeat the step 9 above about 9 times to cover -2 to -5 range with 1/3 decrement.
Now you have bunch of raw files. Good news is that you don't need to process them. You only look at them with Adobe ACR.
11. Open Photoshop. Make sure the Brightness setting in the ACR is 50.
Let's decide the upper limit.
12. Open the files one by one from +2. The peak will gradually move toward the right . Eventually you will see something like the one on the left below.
13. IMPORTANT: Slide the Exposure adjust slider to the left to see if you can move the ENTIRE peak to the left. ( See the one on the right hand side ). If you can, the shot is within the range. If you cannot, it is blown-out.
Now, let's decide the lower limit. This is not as obvious as the upper limit. This can be very subjective, too.
14. Open the files one by one from -2. The peak will gradually move toward the left. Eventually you will see something like the one on the left below.
15. The ENTIRE peak should be still contained. ( Check the left tail hitting the ground )
16. IMPORTANT: Slide the Exposure adjust slider to the right to see if you can move the ENTIRE peak to the right. ( See the one on the right hand side ). You will see that the left tail is dragging over long. You should be able to separate it cleanly. You will get to the point where you cannot separate the peak out of the noise ( or left wall ). ( The Blue tail will drag longer )
In my case with D30, the upper limit was 1/5 sec and the lower limit was 1/500 sec. With the camera in hand, I counted the clicks from 1/5 to 1/500 to find that there were 20 clicks. So, the DR is 6 2/3 stops.
The whole procedure is much simpler than it looks. Once you understand how the lower and upper limits are determined, you can do this quickly.
==
Please, post your result with your Canon DSLR. I volunteer to collect the data.
The DR may look greater than you think. It all depends on how much noise you can take. It is important that everyone measures the lower limit the same way consistently.
Edited by Pondria on Feb 18, 2008 at 10:16 PM GMT (Reason: Data update)
Edited on Feb 19, 2008 at 06:16 AM
|
