This is the sixteenth in a series of posts on the Fujifilm GFX-50S. The series starts here.
A reader has been commenting that he is getting far better results with Otus lenses and his D810 than I’ve been getting with the a7RII, which I’ve been using as a reference camera for some of my GFX testing. This has gone on long enough that I am now motivated to get to the bottom of it, and intend to do so in this post.
But first, I’d like to talk about what I’ve been showing you for the last few days, and how to interpret it. I have been developing the raw files in Lightroom with nearly the default settings (and noting any departures from those settings). I have been exporting tight crops from the developed images as 700-pixel-high JPEGs, and posting them here. That means that the images are all heavily upsampled. The GFX images are 253% of their original size in both dimensions. The a7RII images are at 295%. And the D810 images come out at 317%. The different ratios are necessary to compensate for the variations in the height of the three sensors when measured in pixels.
If you just want a rough idea of the differences, just look at the images as displayed in-line in the posts. However, if you wish to compare these images in detail, you should view these images by clicking on them to see the source files, then setting your browser for 100% zooming. Even better, download them and make Photoshop stacks.
No matter what you do, these crops are all going to look horrible. I’m blowing them up so much so that they will represent the original file after JPEG’s discrete cosine transform has had its way with them. If you want to get a good idea of what the images would look like printed, get far away from your monitor. No, farther than that. Put a bunch of the images up on the screen and back up until the best one starts to look good. Then look at the others.
There’s another reason why these images won’t look like the best thing the camera/lens combination can deliver. They’re demosaiced with Lightroom. Lightroom is not awful, but for a particular image, there are usually better raw processors. I use Lr because it’s a de facto standard, because I know it well, and because it’s got good tools for dealing with groups of images.
The images were made with a Sony alpha 7R Mark II with the Zeiss Otus 55 mm f/1.4 DF.2 lens, and a Nikon D810 with the same lens. While it’s not central to the theme of this test, I will show images made with the Fujifilm GFX and the Zeiss Otus 85 mm f/1.4 ZF.2 lens as well.
Shutter set to EFCS for both cameras, which meant it really was EFCS at the narrower apertures for the GFX. The D810 has a similar EFCS defeat, but that did not some into play here. F-stops were f/2.8 through f/8 in whole stops. Normally I’d go to f/11, but that wouldn’t have affected the point of this exercise, and would have raised the possibility of wind-induced subject motion blur, especially with the Nikon. Exposure compensation set to zero. Manual Focusing for all lenses. I focused three times at each aperture, and picked the sharpest images. 2-second self-timer used in for the GFX and the a7RII; 3-second shutter delay used for the D810. Arca-Swiss C1 cube on RRS sticks. Focus was near the center of the image, and all images were refocused at each aperture. Tripod and head were not deliberately moved between series, though there appears to have been some shift during the camera and lens changes. Small exposure corrections in Lr. Daylight white balance selected in Lightroom.
The entire frame with each camera:
In the center, at roughly 250% magnification for the GFX, and the same vertical sensor extent for the lower-resolution a7RII. This would give the same vertical field of view if the lenses were vertically equivalent focal lengths. Details: the GFX crops are 357×277 pixels, and the Sony crops are 306×237 pixels, and the Nikon crops are 252×195 pixels. All are enlarged to 700 pixels high on export from Lightroom.
Here’s how to use these highly-magnified crops. The dimensions of the GFX sensor are 8256×6192 pixels. If we make a full-frame print from the GFX on a printer with 360 pixels per inch native driver-level resolution, like the Epson inkjet printers, we’ll end up with a 23×17 inch (58×44 cm) print. The 318×246 pixel crop you’re looking at will end up 0.8333×0.6833 inches (2.12×1.74 cm). Let’s imagine that you or your viewers are critical, and will look at the 22×17 inch print from about 18 inches (conventional wisdom is that the distance would be a little greater than that, or 28 inches (the diagonal), but you did buy a high-resolution camera for a reason, didn’t you?).
The next step is dependent on your monitor pitch, which you may or may not know. Turns out, you don’t have to know it. Just take the 253% crops and view then at 1:1. How high are they? Get out your ruler and measure, or just guess. Let’s say they are 6 inches high. 6 inches is about 7 times 0.8333, so in order to view the crops the way they’d look from 18 inches on the print is to view them from 7 times as far away, or 10.5 feet.
Everything here scales proportionately. If the image on your screen is bigger than 6 inches, increase your viewing distance by the ratio of your image height to 6 inches. If you thin your viewers are going to almost get their nose to that print and look at it from six inches, divide that 10.5 feet by 3, and look at the image on the monitor from three and a half feet away.
The images from the D810 and a7RII are scaled to the same print height of 17 inches. Because they have fewer pixels vertically, that require slightly greater magnification.
The Nikon and the Sony images are of the same part of the scene. Because of the lens field of vie differences, the GFX image is of a different part. Note that the chosen scaling leaves the subject size the same in both the a7RII image and the D810 image, even though the two cameras have different resolution.
I could show you corner crops, but I think the center crops prove the point.
In most cases, the lens is plenty sharp enough for the sensor. The D810 images look a bit softer than the a7RII images. I put that down to the difference in resolution between the two cameras. It’s harder to see here because the cropped part of the scene is different in the GFX images, but the differences relative to the a7RII look about like they have in the other comparisons: the GFX is a bit sharper with the Otus lenses, because it is both higher resolution and lower pixel pitch.