Dynamic Range test at home

[IVPhoto]

I wanted to share a method I found for testing the Dynamic Range (DR) of a camera at home. Actually, it's not exactly the DR, as that's often just a marketing gimmick, but rather the usable range of exposure that the camera's sensor can handle.

The DR figures you see in camera specs or in tests, like those from DxO, don't hold much practical value beyond marketing. They simply show that the sensor can detect some shades of black and white at the extreme ends of exposure. In reality, these exposures are useless for artistic photography (examples to follow).

Quote

 

Dynamic range is the range the camera can see from the deepest darkest shadows to the brightest highlights in the same shot. Dynamic range is when can discern visually a brightness change at both ends of the range (dark-bright). So a camera that can resolve 14 stops DR will be able to shoot a scene with a 14 stop brightness range and show some information from stop 0 to stop 14.

One note of caution with published dynamic range figures or measurements is that while you may be able to discern some picture information in those deepest shadows or brightest highlights, just how useable both ends of the range are will depend on just how the camera performs at it’s extremes. It is not uncommon for the darkest stop to be so close to the cameras noise floor that in reality it’s barely useable, but as it can be measured it will be included in the manufacturers dynamic range figures.

Latitude is the range within the dynamic range where we can expose and still get a usable image. Latitude is a measure of just how flexible you can be with your exposure without significantly compromising the finished picture. The latitude will always be less than the cameras dynamic range. The latitude would then be how much can you over expose or under expose and still have an acceptable result.

 

Test Methodology

Take a series of 18 shots with equal exposure steps of a constant light source, preferably a computer monitor. Display red, green, blue, black, and white colors on the monitor, or use a test chart. You can also photograph a phone screen.

The focal length doesn’t matter; just make sure the screen fills the entire frame so the light covers the whole sensor.

Choose an aperture so that at a mid-range exposure (1/15s), the screen is exposed at the center of the histogram. This will be the midpoint of the exposure, and then shoot in the following sequence:

1. ISO 100, 30s
2. ISO 100, 15s
3. ISO 100, 8s
4. ISO 100, 4s
5. ISO 100, 2s
6. ISO 100, 1s
7. ISO 100, 0.5s
8. ISO 100, 1/4s
9. ISO 100, 1/8s
10. ISO 100, 1/15s
11. ISO 100, 1/30s
12. ISO 100, 1/60s
13. ISO 100, 1/125s
14. ISO 100, 1/250s
15. ISO 100, 1/500s
16. ISO 100, 1/1000s
17. ISO 100, 1/2000s
18. ISO 100, 1/4000s

Processing the Results

Open all the photos in an editor. The shot with 1/15s exposure (#10) is the reference image. For the longer exposures, adjust the EV by decreasing one step for each (i.e., bring them down by 1 EV). For the shorter exposures, increase the EV by one step for each.

For example:

1. EV -5

2. EV -5

3. EV -5

4. EV -5

5. EV -5

6. EV -4

7. EV -3

8. EV -2

9. EV -1
    

10. EV 0
     

11. EV +1

12. EV +2

13. EV +3

14. EV +4

15. EV +5

16. EV +5

17. EV +5

18. EV +5

If processing the results is too much trouble, feel free to upload the RAW files to any storage, and I'd be happy to process them for you and share the results.

Results

For example, the usable dynamic range of the Sony NEX-5T, as you can see, is about 9 stops—those where colors aren't ruined by long exposures and where there isn't too much noise at high shutter speeds.

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Edited September 7 by IVPhoto

[Pieter]

Interesting methodology, and somewhat useful I guess. The only thing you're missing here is that you assume the sensor is ISO invariant. Most new Sony sensors have a dual gain sensor, which improves dynamic range at higher ISOs by about 1 stop. In practice this means that you'll get better results if you raise your ISO in camera than to push exposure in post.

You can actually test for this with your procedure by varying ISO rather than shutter speed and then normalizing the exposure in post. You'll likely find that you'll get slightly bigger dynamic range than you did with your first procedure.

[Cameratose]

While DR as posted by DxO and Photons to Photos may be 'marketing', it's still a useful tool to compare cameras since testing is controlled. It's good information to help someone make a decision. As for actual use, I become accustomed to what my camera will and won't do and learn to shoot within those parameters.