Ultra Hi-Res Sensors and the Demise of Pixel Peeping

645d Oct 2, 2011

With 35 mm digital sensors (full frame and cropped) now encroaching into image sizes once reserved for medium format digital (MFD) systems, photographers are going to have to change the way they examine their images for picture quality. With the introduction of the Sony SLT-A77 and NEX-7, cropped (APS-C) sensors have now surpassed the 22 megapixel mark, entering into the medium format image zone. Before anyone runs out to saddle up the high horse, please understand that I am not saying that 35 mm sensors of any flavor are better or worse than medium format digital sensors, just that the image sizes are now starting to overlap.

Full frame sensor cameras from Canon, Nikon and Sony have been in this region for several years now, but the cameras that housed those sensors were relatively expensive (~$8K for Canon/Nikon and Sony ~$2800, roughly) so only professionals and really affluent amateurs had access to them. (By comparison, MFD systems start around ~$10K USD.) Sony’s offerings are a harbinger for what is going to be a new wave of ultra hi-res sensor cameras that are more affordable and thus, more mainstream. On an interesting note, if you scale the sensor technology used to create the 24 mpx sensor in the SLT-A77/NEX-7 up to full frame, you are talking about a sensor in the 36 megapixel range, putting it almost on par (size-wise) with mid-level MFD systems.

The funny thing is when images get that big, everything about them gets magnified too, in a way.

A common practice of the more advanced photographer is to open a file in their favorite photo editor and zoom the image in to 100% view, allowing them to examine images at the pixel level. This practice is called pixel peeping. This is fine,and dandy, but when you are talking about mondo big files like the ones mentioned above, looking at the images on the pixel level can be a bit disappointing. Images look can quite grainy and noisy, especially in poor light/high-ISO conditions. MFD systems, as a rule, rarely shoot above ISO 1600, with ISO 50-100 being preferred for maximum image quality. Phase One, using their Sensor+ pixel binning technology allows for relatively clean ISO 3200 images, albeit at ¼ the resolution of the sensor (i.e. a 40 mpx sensor records 10 mpx images in Sensor+).

Now MFD manufacturers have had to deal with this issue for years and they have perfected their RAW converter software to optimize the images captured by their systems to minimize noise and maintain high levels of dynamic range and astounding color depth (over 281 trillion colors – that’s trillion with a “t”, 12 zeroes, also known as “thousand billion” outside the U.S.) and MFD know that the proof of image quality does not lie at the pixel level, but in the final output.

To wit: I have gathered several examples of images from various ultra hi-res cameras and produced a series of images comprised of 100% crops (pixel level) and images reduced for web consumption. Why web consumption? Simple, even a 24 mpx image would require 12 HD monitors in order to display the image completely at 100% and no one outside of a Nokia engineer’s mother has the bandwidth to see images that size with any speed.

I understand that this comparison is highly unscientific. The images are captured in a variety of lighting conditions, different lenses, and various ISO levels (one at ISO 50). The point is, when the image is prepared for its final output, all of the horrible details we have been seeing at 100% crop go away.

Here a shot from Leaf Aptus-II 8 MFD back (40 mpx) on a Phase One 645DF camera at ISO 50:


and now the ill image reduced to 1000 px high for web viewing:


As you can see the image is very, very clean and sharps with tons of details in the cactus.

Next we have a Hasselblad H4D-40 shot with a 100 mm f/2.2 lens at ISO 800. First the crop:


Now the full image reduced to web size:


Even at ISO 800, the Hasselblad H4D-40 and the Phocus software do an excellent job of mitigating noise. The HC 100mm f/2.2 is a frighteningly sharp lens.

Next up is an ISO 200 shot from a Pentax 645D – first the crop:


and now the web scaled full image:


A little bit of grain can be seen in the crop but it vanishes entirely in the full image. It should be noted that the 645D can only 14-bit capture as opposed to the Aptus-II, H4D-40, and (below) Phase One IQ180 which can capture 16-bit color.

Next is the IQ180, Phase One’s top of the line 80 megapixel back – first the crop:


and now, the web image


These were shot at ISO 100. Please note that the above images were all shot in the appropriate RAW format and the native RAW converter was applied except for the Pentax 645D where Lightroom 3.5 was used. The software has been optimized to reduce noise in each case while maintaining a high level of detail. Another mitigating factor here is lens quality. The H4D-40 + HC 100mm f/2.2 has lens correction data stored in the lens and transmitted to the digital back to be encoded into the image for later processing. The Phase One image was shot with a Schneider Kruzenack 110mm LS lens (arguably one of the sharpest lenses on the market). I do not have lens data for the Aptus-II 8 or 645D shots as I did not take them. I will update this document if that information becomes available.

Now shots from the Sony. It would have been better to compare images from MFD systems of similar resolution, such as the Phase P25+ and the H3D-II/22 but neither of those cameras were available to me. Also, these shots were taken with a pre-release camera and prototype firmware, and processed with Lightroom 3.5 (which has first gen support for the A77).

First the crop:


and now the web sized full image:


The crop is a bit noisier than the crops from the MFDs, it is also the lowest resolution image in the bunch with the smallest pixel pitch. It is, however, at twice the ISO of the highest possible in the MFD. Be that as it may, when you reduce the image to the intended medium (web, in this case) the image is perfectly usable with a pleasant grain effect. It would probably make a great B&W print.

And what was the point of this exercise?

To show that pixel peeping isn’t quite as useful at these ultra hi-resolution sizes. The proof is in the final destination for your image, be it print or online.

Thanks for reading!