But I getting ahead of myself. Let me start at the beginning.
If you've been a follower of this column, you know that, among other things, I also take photographs to make into very large (5-8' width) prints. Achieving high resolution at this print size while using modern, full frame digital cameras puts a strain on the camera sensor as well as the optics, not to mention the photographic technique itself. For the first part of the equation, I have been using two cameras for most of this work -- the 36MP Nikon D810 and Leica M 240. I have been using the D810 because of its exceptional sensor, and the Leica M because it takes Leica-M lenses. One thing I have noticed is that the images coming from my Leica camera always appear to be noticeably sharper than images from any other camera I use. I attribute this primarily to the optics. Then D810 is also very good, but its quality comes primarily from its sensor. Nikon optics, while really good, are not on a par with the best lenses being made by Leica and Zeiss for digital cameras.
One thing I have learned from using high resolution sensors is that they are not forgiving. If you don't have the best optics and exhibit meticulous technique -- tripod only, no hand-holding -- the results are going to be terrible, often even worse than using a camera with fewer megapixels.
I ran some specific experiments using the same Leica-M lenses on both cameras and, sure enough, Leica-M lenses on a Leica M body produced sharper overall results. I became discouraged to the point of considering selling off my new A7rII. This is not to say the A7rII is not a great camera, despite the numerous short-comings I find in the way it handles. The sensor is exceptional. But the sensor is only half of the equation. Using the lenses Zeiss makes specifically for it would probably deliver the results I require. But putting the same lenses on my D810 would probably achieve similar results and, although touted for its diminutive size, the bulk of an A7rII builds rapidly as you mount quality Zeiss optics on it.
My dilemma led me to try an experiment in post-processing. I always shoot in camera RAW and process my images into 16-bit tif files using Adobe Camera Raw. I find this program to be exception and do most of my processing with it, leaving only minor adjustments to be made in Photoshop later.
When outputting a file from ACR, you have the option of changing its size. One way of doing this is to change the megapixel count. Doing so will obviously result in a larger file size. What I have noticed is that the results from this up-res are better than by trying to increase the size later in Photoshop.
|This is where I choose the megapixel size to output from ACR.|
In addition to the sizing the image to 42MP, I also add a tiny bit of sharpening. Over-sharpening a Leica image is very noticeable so be careful with this. It must be done sparingly. How much depends upon the individual file.
The samples below illustrate a comparison between a Sony A7rII and Leica M 240 over-clocked to 42MP. Both cameras used the same Leica 50mm Summilux lens at f/5.6.
|This is the entire scene photographed. The excerpts below show the lower left corner at 100% magnification.|
|You can download this comparison photo here. I chose to use a corner because it is an area that is less forgiving in terms of sharpness.|
The photo below, a composite of ten vertical images taken in two rows of five photos each with the Lecia M 240 and Leica 50mm Summilux lens is typical of the results I need to achieve for my large prints. The final print size for this image is 28x60".
|Download a high-res sample of this image here. I had to make it smaller than the full 28x60" size so as not of over-tax my file server. Nonetheless, it is still large enough to give an idea of what this technique is capable of delivering.|