5DS vs 5DS R Accutance, Resolution, and Artifact Comparison.

   Canon's new high resolution cameras, the 5DS/R have reignited the debate over the virtues and cost of having an optical low pass filter (OLPF).  Thus far the posted samples appear to show a clear sharpness and resolution advantage for the R version.  I have been wondering how much of this apparent advantage is real resolution and how much is simply a difference in accutance that can be corrected for in post processing.  With DPreview posting studio samples from the cameras, there is now a high quality comparison available.  I have opened the raw files directly into Lightroom and only adjusted the sharpening as specified below.

   The first images are the raw files loaded directly into Lightroom with the default sharpening setting of Amount = 25.  The crop from the studio scene has been chosen deliberately to emphasize both resolution and color artifacts.  Neither effect should be as strong in most real-world images.  Clearly the SR version has higher accutance and displays stronger color artifacts as expected.  Interestingly, the S version isn't completely artifact free implying that the OLPF isn't strong enough to completely eliminate aliasing.

Left: 5DS Sharpening = 25.  Right:  5DS R Sharpening = 25.

   The second set of images has a bit of sharpening applied to the S version.  Clearly a little sharpening goes a long way and increases the accutance and thus the apparent sharpness significantly above the SR version.

Left: 5DS Sharpening = 50.  Right:  5DS R Sharpening = 25.

    In this third set of images, has equal sharpening applied to both images.  The SR again leads in accutance but has become over-sharpened.  To come back to an appropriate level for a print, the sharpening needs to be backed off.

Left: 5DS Sharpening = 50.  Right:  5DS R Sharpening = 50.

   This final set of images has the sharpening set such that the accutance looks roughly equal to my eye.  Unfortunately this is rather subjective.

Left: 5DS Sharpening = 50.  Right:  5DS R Sharpening = 35.

The differences between the two images are now pretty subtle.  Upon close inspection there are some apparent details that are clearly visible in the SR version that do not show up as well or as clearly in the S version.  The SR also shows stronger color artifacts, as expected.  In the end the difference between the cameras is splitting hairs.  The S version seems to tolerate sharpening better, but also needs a bit more of it.

Personally, I am willing to give up a slight amount of detail in exchange for not having to deal with as much aliasing or as many color artifacts.  As has been demonstrated by the popularity of AA-less cameras over the last several years, others may find the SR version better for their needs.

The Image That Convinced Me to Anti-Alias

    As a Canon user, I watched cameras from Sony and Nikon outresolve my Canons by virtue of higher pixel count and lack of an anti-aliasing filter / optical low pass filter (OLPF).  I had assumed that Canon kept the OLPF around for their professional customer base but that I, as a landscape photographer, would not encounter the fine mesh patterns that the OLPF is needed for.  This sample image from Canon changed all that:

http://www.usa.canon.com/CUSA/assets/app/images/cameras/eos/EOS_5DS_R/sample_images/03.jpg

If we zoom into the reflections on the side of the hippo, there are severe color artifacts.

Crop from above.  Note the red, green, and blue color artifacts scattered in the reflections.

    The level of detail and sharpness that the AA less 50MP sensor provides is incredible, but the color artifacts render the image severely damaged.  A different demosaicing algorithm could potentially eliminate the artifacts, but not without significant loss of real detail as well.  The potential for color errors is not limited to man-made subjects, but can occur in images of any kind.

    It is worth noting the conditions in which color artifacts are most likely.  The subject must have high contrast details at a high spacial frequency and the optical system must be good enough to properly resolve those details.  Specifically, the lens must be perfectly in focus, at an aperture wide enough to limit diffraction, and sharp enough at said aperture.  The hippo shot was with a 500mm f/4 L IS II @ f/4 and so certainly meets those criteria.

   I am now grateful to be presented the choice of an OLPF and am asking myself "is the small increase in resolution worth the chance that a portfolio quality image would be ruined by aliasing or artifacts?"  Sadly for the pixel-peeper in me, I think not.

A Reasonable Backpacking Tripod

While hand-holding can work just fine for most general daylight photography, a tripod is critical as the light fades and the best photographic opportunities arise.  A tripod is also necessary for many techniques used to enhance final image quality including but not limited to HDR, nodal point panoramas, and focus stacking.  Unfortunately for our purposes, tripod stability is highly inversely correlated with tripod heft.  Thus my goal was to find the absolute lightest setup that will reasonably hold a full frame DSLR with an attached f/2.8 zoom.

In addition to an excellent strenght/weight ratio I look for twist leg-locks and an Arca-style quick release for speed of deployment and a bottom hook for hanging weight.  My solution consists of the following:

Oben CT-2331 - 26.4oz (http://www.bhphotovideo.com/c/product/864593-REG/oben_ct_2331_3_section_carbon_fiber.html)

Really Right Stuff BH-25 - 4.1oz  (http://www.reallyrightstuff.com/Shop/BH-25-Ultra-Light-Ballhead/BH-25-Ultra-light-ballhead-no-clamp-no-platform.html)

Sunwayfoto DDC-37 - 1.55oz (http://www.amazon.com/SUNWAYFOTO-DDC-37-SunwayFoto-Screw-Knob-Clamp/dp/B00BFD7Y4Q)*

*This Arca-style clamp has an M5 mounting hole that needs to be drilled out for compatibility with 1/4-20.

After removing the mounting platform from the tripod and screwing the head directly onto the center column, the total weight comes to 1 lb, 12 oz.  This gives the tripod the following specs:

Height without center column extended -   47"

Height with center column extended-         56"

Folded length-                                          21"

Weight-                                                   1.75 lbs

Manufacturer weight rating-                       8.8 lbs / 4 kg

Using the typical rule for tripods of:

Practical weight rating = Manufacturer weight rating / 2

this tripod should hold the 4 lb weight of my 5DS and 24-70 F/2.8.  There is only one way to find out for certain and is a good excuse to play around with camera equipment.  Lab test!  For the following test I shot a test chart with the 5DS and the 24-70 f/2.8 ii @ 70mm f/5.0, ISO 100, 3.2s exposure.

This is an 8:1 crop.  We can see that critical sharpness has been achieved.  However, I did have to use a cable release or >0.5s mirror lockup with the on camera shutter release to achieve stability.

Note that there are some subtle color shifts in the image.  These are imaging artifacts and not real despite the anti-aliasing filter on this camera.  Intriguing, but the subject of another post. 

The number of tripod and ballhead choices out there are absurd compared to even ten years ago.  I could not have researched every possible combination so please share what you have come up with!

I Shoot Canon ... For Historical Reasons

I will make repeated references to the equipment I am using in various tests and experiments.  This will invariably some sort of Canon DSLR and lens combination.  I expect the reader to have the following instantaneous befuddlement: "If this guy is so interested in maximizing image quality and reducing weight for non-moving subjects, WTF is he doing using Canon DSLRs???"  Good question.

The answer is a mix of cost considerations and historical reasons.  I began shooting with Velvia and a Canon Elan 7e way back when.  My lens collection grew from there to where I find myself now with a beautiful set of Canon glass.  I currently shoot with a 5DS, 24-70 f/2.8 II, 16-35 f/4 IS, 70-200 f/4 IS and some assorted primes and older bodies.  It is simply not economically viable, and in some aspects not possible, to switch systems and maintain such a high level of image quality.

I also want to diffuse any notion that I am religious about my choice of gear.  There are at least a dozen camera systems out there that when used with good technique and vision, will produce phenomenal results.  If I were to start from scratch today, I would likely end up in the Sony A7xx/FE mount universe.  The cameras are light with superb image quality.  The few available lenses are all of high quality.  But the equipment I have is also fantastic weight difference of a pound just isn't enough for me to switch.

Searching for the Gigapixel Camera Phone

Two of my favorite hobbies, backpacking and photography complement each other exceptionally well.  Except in one department, weight.  Image quality tends to scale with camera size.  Bigger sensors have lower noise and higher per-pixel resolution.  Larger sensors require heavier lenses.  Heavier lenses demand beefier tripods.  Conversely, every ounce taken off of the pack is that much more enjoyment on, and mileage of the trail.  This blog is simply a documentation of my efforts of optimization and studies in compromise.