One of the things that you hear on the Interwebs is that when you buy a mirrorless camera, you may have to just grind down all your existing legacy glass to dust and dispose of it responsibly because the blood-sucking hordes of chromatic aberration are going to destroy your mind, break down your body, and leave you a gasping husk of a photographer begging for death's merciful release. But is that really true? Well, for one thing, even modern up-to-the-minute lenses are going to show some CA on today's sensors if you torture them enough. By this I mean, if you insist on pointing even a modern lens produced yesterday directly at your back-lit, detailed subject, and zoom in on the subject's edges on-screen against the backlighting you are going to notice some sensor bloom and CA. I have seen enough of Sean Reid's lens reviews to know this for certain.
And it is true that older lenses, designed film in mind instead of a digital sensor are going to have this problem. But it's like the old Vaudeville Dr. Kronkite joke. Man goes to "Dr, when I raise my arm like this, it hurts." Dr: "so don't do that."
The Pentax Takumar M42 (what used to be called universal screw-mount) lenses are beautifully built, all brass creations. I don't think there is anyone out there making lenses of this build quality today -- maybe Leica. They can still be had for a reasonable price, are compact, and fun to use. But will they perform? The punchline is, of course, that you all are going to have to decide for yourselves, but this morning I put a 105/2.8 Takumar lens on the Nikon Z8 to see what would happen.
Here's a shot of the blooms on the maple tree in the backyard with that lens wide open. The maple blossoms are funny flowers, and are often among first thing that the local bees go for when spring sets in around here. First the crocuses, then the daffodils, then the maple. It has been like that every spring since we moved here:
That's a shot of the blooms at minimum focus of about 1.2 meters. As you can see the subject is isolated by the f:2.8 aperture and the OOF areas are pretty smooth. The sun is behind me, so this isn't a torture test, but you can see a little smearing/CA in this 100% crop from the above shot:
Here's the same shot at f:8:
As you can see, there is less CA, and the perceived result in the picture is higher contrast. I should mention that these are jpg conversion from PS with no corrections applied. What you are seeing is about .3% of the data that the sensor produces. I'll return to that below with some links to full-size JPGs.
Here's a 100% area crop from the second picture:
To my eye, this cleans up nicely. Now you might be thinking that being "constrained" to shooting at f:8 would be a drag. But it does suggest that whatever the native quality of the glass is wide-open, you do have some tools to control this if that's the direction you want to go.
But what about an actual torture test? What's the use of cherry picking performance with the sun at my back? So here's a shot of a pine tree, shot up against the open sky:
There's definitely some CA there. . . I can feel the purple greeblies reaching out even at this reduced image size. Here's a crop, viewing the worst of it at 100%:
Yuck, right? Well, what about PS Camera RAW's check box for removing CA on conversion? MMMMMmm, it helps, but doesn't eliminate the problem. The above is a straight conversion with no attempt at digital "help" from PS. Here's the same crop from a version of the file with Camera RAW's CA box clicked, "help meee . . . ."
Not much help, to my eye.
So is the "problem" of legacy glass one that is insurmountable? Well, I am going to argue "no," but you have to kinda know what your tools are going to do before you press the shutter button. Today, the eFray price for a clean 105/2.8 Takumar is $89 plus $17 shipping from Japan. That's a pretty sweet deal in lens-land, even if it is more than these things were selling for a couple of years ago.
Here are some other shots for comparison. f:2.8:
f: 8 (different focus point, though):
Here's another at f:2.8:
And at f:8:
F: 2.8 again (you're getting the idea by now):
Finally, I have posted links below to 10 MB versions of jpg of a couple of the above. I dunno, I have to figure out whether Smugmug can take 8-bit TIFFs. The best way, I think, to see what's going on with these is to have copies of the files to play with on your own set-ups. But for now, the links go to larger versions of a couple of the above shots. If you think "larger images might convince me," download 'em and look.
My own conclusions is that the old Pentax M42 lenses can do great, especially for the price. I feel almost like families of lenses can give photographers a particular color palate, or "look" that would be hard to re-create digitally (or would take more time sitting in front of the computer than I want to put in). I will use this lens without particular fear of its CA properties, but will also have to take some care about shot placement vs. light source. Then again, we all do that anyway when we are working at our best. The nut behind the trigger release is responsible for how the picture turns out . . . including where he or she is placed in relation to the light. Apologies for the boring nature of the pictures. But that's what its like in my backyard after only one cup of coffee.
https://benjaminmarks.smugmug.com/Nikon-Z8-Full-Size-Test-Files/i-p9XPNC4/A
Nikon Z8 Full Size Test Files - Marks Imaging LLC
Nikon Z8 Full Size Test Files - Marks Imaging LLC
Nikon Z8 Full Size Test Files - Marks Imaging LLC
Edit: I can actually imagine a use for a portrait lens with a little softness wide open. There used to be LF portrat lenses that came with a series of diffuser disks allowing the photographer to dial in the amount of diffusion he wanted in the final portrait. You could think of this lens as a portrait lens for subjects of a certain age. I'm as vain as the next man and I wouldn't mind some of my more common defects softened a bit when the camera comes in for a close up.