08/15/16 A close look at the Dynamic Range of the Phase One IQ100
I have been using the IQ100 now for several months, and have noticed that there are some interesting facets to the dynamic range of this digital back. Lets take a more detailed look at this particular image taken on the Buffalo River, in Arkansas
The IQ100 is of course the first 100MP digital camera ever marketed, was introduced in January of 2016 by Phase One, and so far has had a very good reception. I was very interested in the previous IQ250, 50MP digital back, however it has a 1:3 crop factor, which for my work, (example this image) would have been too much to sacrifice. I use wide angle lenses in most of work unless I am stitching and the 30 percent loss in focal view was too much for me. But I easily saw with the IQ250 the massive advantages that CMOS had over the traditional CCD Phase One backs. This showed up for me in two main areas, noise and dynamic range. These both have many definitions but for me it’s simple:
Noise, how much noise will I see in areas of shadow, at base ISO and at higher ISO. If I push an image, how much detail is lost to noise in the shadows. With a CCD back, there was never too much room here even at base ISO of 50
Dynamic Range, with one single exposure, what can I capture? If I adjust for highlights, will my shadows be filled with too much noise or vise versa. Also how well does my color saturation hold up at higher ISO ranges. With CCD digital backs, the color saturation fell off very quickly once past the base ISO. You might be able to get one more stop before the saturation was lost.
Moving to the IQ100 from the IQ260 I was hoping to see similar if not greater dynamic range at base ISO to the Nikon D810. I still regard the Nikon D810 as the flagship for dynamic range at base ISO of 64. With the Nikon D810 it’s easy to push a single exposure as much as 2.5 stops and still have wonderful details in the areas of shadow. Phase One (P1) rates the IQ100 at a base ISO of 50 so I was hoping to be able to get at least 2 stops of details when shooting at ISO 50. So on my first couple of outings with the IQ100, I mainly used ISO50 and planned to push the shots when necessary. I quickly found out that this the chip in the IQ100 (made by Sony) behaves differently that the 36MP chip in the D810 (also by Sony).
In working at base ISO 50, it became apparent to me that a shadow push of even 1 stop may be enough to cause you to lose details in the shadows, and also a huge amount of color saturation. This was a surprise to me as I had expected to get even better push than what I was seeing with the D810. However it was also soon apparent that the IQ100 has quite a bit of leeway with highlights, much more so than any of the CCD backs I have used from Phase One in the past. You can easily let your highlights go past 1 to 1.5 stops and still regain the finer whites. If you combine the “highlights” slider in Capture One, along the exposure slider, there is a lot of recovery. Looking at the example below: Click on the image to view it larger
The image on the right side is the base image before any adjustments, the image on the left side, I just pulled the overall exposure down from center to -99 (almost 1 stop) and then adjusted the highlights to 47 from the far left. This pulled back all of the sky and actually provided some very nice cloud features. I then just added a local adjustment layer to the lower portion of the file, (non sky) and pulled up the overall exposure then added one more adjustment layer to tweak a few dark areas. Overall the end result to me is very nice and again is testimony to just how much range is in a single exposure from this chip. The take away is for sure feel free to let your highlights go a bit so that you can pull in a bit more shadow details.
Here another example.
Here the original raw file is on the left side. Initial thoughts are that the sky is pretty blown, but with just a bit of highlight adjustment and overall exposure work, you can pull back the sky to a very manageable level. The bluff and trees will easily recover to most of their full detail with a bit of shadow recovery and local adjustment layer to work only on that part of the image.
From my photography I feel if there is a downside to the IQ100 dynamic range, it would be in the shadow recovery. Here you have to be very careful as just one stop or two can make a huge difference between good details and color in the shadows. Lets go back to an example from the same set of images. If you look at the image at the top of this article, you can see that towards the far right on the bluff there is a dark area. I shot this scene in several brackets at both ISO 50 and 100 as I was unsure as to just how the clouds would capture. As it turned out, the clouds/sky were not the problem, but the dark shadows were. Look at this comparison: make sure to click on the image to view it full screen.
The image on the left was shot at ISO 50 at 1/25th of a second, F12, and the image on the left was taken immediately next at ISO50 and 1/60th of a second F12. If you click on the image, you can see that the bluff and trees along the bluff are almost devoid of color and there is considerably more noise. Both of these screen crops are from sharpened final images. The image on the left holds the green down into the shadows where as the same part of the image on the right is starting to lose the color fidelity. The color you may be able to pull back with some work in Photoshop, but the noise and loss of overall details you will never get back. So the point, is that you really need to watch your exposure and if you are unsure, bracket the frames. Just a difference in 1/25th and 1/60th can make a big improvement in the overall quality of the final image.
I feel that there is considerably more dynamic range in the IQ100 CMOS back, over similar CCD backs like the IQ260 and IQ380 (60 and 80MP respectively)
The IQ100 has a tendency to push to a green overall tint and it seems that the greens can easily be come over saturated.
When working in mixed outdoor lighting, I would recommend exposing to the right, and pushing the highlights, as from my shooting experience you can easily recover 1 stop and possibly 1.5 stops in the highlights.
The shadows will quickly loss details and color if underexposed, even at base ISO of 50 or one push to ISO100. Once these details are lost you will not be able to get them back easily.
Considering that the 100MP back will start to suffer softness from diffraction at apertures past F11, you need to balance your shooting between both shutter speeds (subject allowing) and ISO.
When working on a single file, don’t be fooled into thinking that you have lost your highlights as you will be surprised to see just how much dynamic range and malleability is available in these fantastic files.