UNDERSTANDING RAW

1. UNDERSTANDING RAW Joe Sukenick DigiQuest www.DigiQuestPC.com

2. What is a RAW file?

3. What is a RAW file? A representation in binary format of the photons (particles of light) falling on the camera’s sensor, and recorded as voltage levels in binary format, then stored in a file in the camera’s media (compact flash card, SD card, memory stick, etc.)

4. Canon uses CRW and CR2, Nikon uses NEF, and Fuji uses RAF to denote RAW files.

5. Canon uses CRW and CR2, Nikon uses NEF, and Fuji uses RAF to denote RAW files. * Most cameras capture in 12 bit and have 4,096 levels per channel.

6. Canon uses CRW and CR2, Nikon uses NEF, and Fuji uses RAF to denote RAW files. * Most cameras capture in 12 bit and have 4,096 levels per channel. * Cameras that capture in 14 bit have 16,384 levels per channel.

7. Canon uses CRW and CR2, Nikon uses NEF, and Fuji uses RAF to denote RAW files. * Most cameras capture in 12 bit and have 4,096 levels per channel. * Cameras that capture in 14 bit have 16,384 levels per channel. * JPEG is 8 bit and has only 256 levels per channel.

8. Each photosite (pixel) on the sensor has a filter that allows it to capture only RED,GREEN, or BLUE data.

9. Each photosite (pixel) on the sensor has a filter that allows it to capture only RED,GREEN, or BLUE data. The camera’s firmware (similar to the operating system in a computer) looks at adjacent pixel information, then calculates full color information from the data.

10. A RAW file is NOT a viewable image.

11. I don’t believe you, “Mr. Smart Guy”. I shoot RAW only and not RAW + JPEG. As soon as I shoot a RAW image, I see the results on the back of my camera from that raw file. You must be wrong!

12. You are looking at a JPEG thumbnail image created from the RAW data. RAW data must be converted to a viewable file format as a JPEG, TIF, PSD, or other image format before you can view what was captured in the RAW file.

13. The camera’s Analog to Digital converter processes the RAW data and converts it to a JPEG thumbnail image. You can now view the image, histogram and metadata information in-camera for the image that was captured.

14. The JPEG image is created using the camera’s default settings.

15. The JPEG image is created using the camera’s default settings. This is an opportunity for our cameras to lie to us and compromise our image quality. More about this later…..

16. Suppose you put one marble in your hand. Then you put a second one in the same hand. It feels heavier, but it doesn’t feel like it weighs twice as much.

17. If you put one teaspoon of sugar in your coffee, taste it, and add a second teaspoon. It’s sweeter but does not taste twice as sweet.

18. If we view an object lit by one 100 watt bulb and then place a second 100 watt bulb right next to it, we doubled the amount of light on that object. It appears brighter, but it doesn’t appear twice as bright.

19. Our senses will normally respond to stimuli this way. It’s called: COMPRESSIVE NONLINEARITY

20. Our senses will normally respond to stimuli this way. It’s called: COMPRESSIVE NONLINEARITY Film responds to light similar to the way the human eye responds to it… with compressive nonlinearity.

21. Our senses will normally respond to stimuli this way. It’s called: COMPRESSIVE NONLINEARITY Film responds to light similar to the way the human eye responds to it… with compressive nonlinearity. This nonlinear response is called a Tone Curve or Response Curve.

22. The huge difference with digital capture is that the sensors in our cameras record light in a LINEAR manner.

23. Response Curves Typical FILM Curve Digital Capture Curve Non-Linear Linear

24. If we were to view a RAW file with no tone curve applied, it would have very little contrast, low saturation and its overall appearance would be dark and “muddy” looking.

25. If we were to view a RAW file with no tone curve applied, it would have very little contrast, low saturation and its overall appearance would be dark and “muddy” looking. The camera applies a tone curve (a form of compressive nonlinearity) to the image when it creates the JPEG thumbnail image.

26. The tone curve it uses to create the thumbnail typically comes from the camera’s setup options.

27. The tone curve it uses to create the thumbnail typically comes from the camera’s setup options. These JPEG options can include: contrast, saturation, white balance, color tone, and other settings that may be camera or manufacturer specific.

28. The tone curve it uses to create the thumbnail typically comes from the camera’s setup options. These JPEG options can include: contrast, saturation, white balance, color tone, and other settings that may be camera or manufacturer specific. They affect how the JPEG is produced.

29. Here is where we can get into trouble. When we view the histogram to evaluate exposure, we are not looking at the RAW data we captured. The histogram we see is from the JPEG thumbnail the camera created using the camera’s JPEG settings!

30. Typical Scenario: We are shooting formals in the church * We expose for 1 stop less than the ambient background light

31. Typical Scenario: We are shooting formals in the church * We expose for 1 stop less than the ambient background light * We set our strobe or flash for a good exposure on the subjects

32. Typical Scenario: We are shooting formals in the church * We expose for 1 stop less than the ambient background light * We set our strobe or flash for a good exposure on the subjects * Our histogram shows we are overexposed and we have some “blinkies”

33. * Not wanting to have blown out highlights, we lower the flash output

34. * Not wanting to have blown out highlights, we lower the flash output * Now, good histogram and no blinkies

35. * Not wanting to have blown out highlights, we lower the flash output * Now, good histogram and no blinkies If we were shooting JPEG’s, did a custom white balance, and we usually like what comes right out of the camera, we are done.

36. If we were shooting RAW, we most likely have an underexposed shot.

37. If we were shooting RAW, we most likely have an underexposed shot. When we viewed the histogram and blinkies, the JPEG tone curve that was applied increased the exposure of the thumbnail to make it appear the RAW data was overexposed. We compensated by lowering the exposure that may have been correct.

38. How do we know how much we are “off ” between the histogram and the actual data captured? When we open our RAW images in our converter (Capture One, Adobe Camera RAW, Lightroom) and many of our images are underexposed and we compensate by increasing the exposure in our RAW converter, it’s off.

39. There is a difference between all the RAW developers in the marketplace. They do not all use the same tone curves to develop images. There will be discrepancies with the same model cameras and how the sensor captures images that can vary up to a half stop between cameras.

40. OK… What do we do? * Ruffle some white shiny fabric, a white sheet, and some black fabric over something and photograph it in RAW mode. Overexpose by 1 stop.

41. OK… What do we do? * Ruffle some white shiny fabric, a white sheet, and some black fabric over something and photograph it in RAW mode. Overexpose by 1 stop. * Note where the camera histogram falls on the camera display and note the blinkies.

42. OK… What do we do? * Ruffle some white shiny fabric, a white sheet, and some black fabric over something and photograph it in RAW mode. Overexpose by 1 stop. * Note where the camera histogram falls on the camera display and note the blinkies. * Open the RAW image in your RAW converter using “Standard” settings and compare results to the camera.

43. * If the camera shows overexposure and the RAW converter does not, (which is the most likely result) adjust your camera settings to lessen contrast, saturation, and tone - then retest.

44. * If the camera shows overexposure and the RAW converter does not, (which is the most likely result) adjust your camera settings to lessen contrast, saturation, and tone - then retest. * Repeat the test and compare until they are close.

45. * If the camera shows overexposure and the RAW converter does not, (which is the most likely result) adjust your camera settings to lessen contrast, saturation, and tone - then retest. * Repeat the test and compare until they are close. * Your camera histogram is now calibrated to your RAW converter.

46. If you do the test, and adjusting the camera settings do not affect the histogram when shooting RAW, your camera may have a standard tone curve applied to all images that ignores the camera settings. If this is the case, you should make a mental note of the allowable blinkies on the camera that are really not overexposed when viewed with your standard RAW converter settings.

47. * Different RAW converters apply different tone curves for the conversion. It is important that you calibrate to the RAW converter you always use. * The same RAW converter may change the tone curve in a new release of the software.

48. Camera manufacturers tend to bias the way the camera displays exposure toward underexposure with the histogram and blinkies. This is done to ensure the highlight information is captured without “blowing out”. They consider this to be more of a problem than blocking up the shadows.

49. Remember, It’s not a “bug” it’s a “FEATURE” to help us!

50. Conclusion: Is RAW that much better than JPEG?