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ReggieB

Dynamic Range and Color Depth: Let's step it up!

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As I stated in my first blog post, this one is where I will begin to criticize the Four-Thirds sensor. Most criticism comes from those who argue for better performance at high ISOs from our sensors because of a perceived (and inaccurate) inferiority at minimizing noise. I have, I think quite well if I do say so myself, argued that when you bring lenses in to the equation, Four-Thirds is the best crop-frame system available for its low-light performance. I stand by this assertion, but I am not here to blindly defend Olympus and Panasonic, but instead to encourage those of us who are their most loyal customers (and most heavily invested in to their systems) to put pressure where pressure is due. It is time for Panasonic, who has caught Canon and Sony in their sensor producing capabilities (Sony makes Nikon's sensors for those confused as to why I jumped from a CaNikon comparison to a CaSony one). Panasonic needs to improve color depth and dynamic range in its sensors.

I spared readers an explanation as to what high ISO noise actually is, since most people are fairly familiar with it. It is easy to understand, because you can see it. Color depth and dynamic range tend to more often come down to what you don't see. Color depth “indicates to what degree of subtlety color nuances can be distinguished from one another, often meaning a hit or a miss on a pantone palette. Maximum color sensitivity reports, in bits, the number of colors that the sensor is able to distinguish...The higher the color sensitivity, the more color nuances can be distinguished.” (DXO Labs definition: http://www.dxomark.com/index.php/en/...cores#Portrait) Dynamic range, simply put, is the amount of detail that a camera can retain in the highlights and shadows of an image.

Both landscape photographers, interested in dynamic range, and portrait photographers, interested in color depth, tend to leave ISOs very low. Usually the lowest setting available for their camera. So these specialists tend to not worry about high ISO noise, which is why most medium format cameras have major noise issues, but their users don't care and still pay upwards of tens of thousands of dollars for their camera bodies. Most of us mortals want a system that is well rounded, we can not afford a Hasselblad for the studio, a Four-Thirds camera for when we want full resolution, fast shutter speed shots with long optics (the 2x crop factor aiding here) when we are doing nature or sports photography, and a full frame, low resolution (ala the D700/D3s) for low-light photography. So we look for a system that does all of these things relatively well.

Four-Thirds sensors are behind in this regard, not by a huge margin, but a noticeable one. In a comparison of the GH1 with the Canon 7D and Nikon D300s, you find that the 7D beats the GH1 by a margin that is imperceptible (at ISO 100), but the D300s is well ahead (about double the minimum thresh-hold for what DXO labs considers a perceptible difference in color depth, and a difference that is .1 EV more than what DXO considers a perceptible difference in dynamic range). Interestingly, you will see in the chart below, that beyond ISO 200 in this comparison, the D300s falls from 1st to 3rd. While it is typical for dynamic range to drop quickly as ISO increases, the 7D registers an imperceptible drop off from ISO 100 to 200, because it starts with this flat curve, above ISO 100, the 7D passes the D300s and moves in to first place for the remainder of the comparison. The GH1 sees a generally steady, but less steep, drop-off moving it in to second above ISO 100.



Color sensitivity is another area where the GH1 lags behind, but this time for an interesting reason. Again, DXO labs asserts that color depth performance is most important at ISO 100, because it is most important to portrait photographers who are dealing with lighting that allows to never shoot at an ISO higher than this. The reason that I argue that the GH1 beats the competition regarding high-ISO noise, is the reason it lags in color sensitivity. The measured ISO (by DXO standards, see my last blog post for more on this) is 137 when the GH1 is set to ISO 100, whereas the 7D is at 94, and the D300s is at 113. At ISO 200, the D300s is at a measured ISO of 139, just 2 above the GH1's ISO 100 setting. The difference between the 7D and the GH1 is just below what DXO labs consider the threshold for a perceptible difference in color sensitivity, yet the GH1's ISO is significantly higher at its own lowest setting. If the GH1 could have its ISO (or the gain on the sensor) set lower, it would likely best the 7D.



I didn't mention the tonal range before, simply because it is a dead heat between the 3 cameras.



To put all of this in to perspective, let's be clear that I am nit-picking, these three cameras' sensors are, shortly, the best of crop-frame. I would also like to make note of the overall scores for the three cameras. According to DXO, “a 5-point difference on the scale corresponds to a gain or loss of sensitivity of 1/3 of a stop.” (http://www.dxomark.com/index.php/en/.../Sensor-Scores) The Canon 7D is 1 point ahead of the GH1, and the Nikon D300s 6 points ahead. These are slight differences, and prove that Four-Thirds sensors are very competitive with APS-C sensors, more or less across the board. I say that Four-Thirds is still behind in color depth and dynamic range, and it is, but only just. The E-3 displays a color depth that equals the GH1, with an imperceptible disadvantage to the 7D, and a difference that is just perceptible with the D300s, but it lags further in dynamic range (indicating that Panasonic is, in fact, working on the issue).



My next post will highlight why what many have said before is true, Olympus needs to switch to the newer Panasonic sensors, because they are significantly improved over the sensors Oly is currently using.

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Comments

  1. John Perriment's Avatar
    More facinating information, Reggie, and excellent presentation. Very much looking forward to Part 3.
  2. Alan Clogwyn's Avatar
    And there you have it, the exact reasons I chose my GH1 over a higher spec Oly.
  3. pepper's Avatar
    Reggie I came across your blog on here from a link on another website! Thank you for all the hard work you've put into this and I too can't wait to see part three.