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The FA75 and the A75 attract considerable favorable comment as being sharp and a good value. These were the standard normals for the 645 film cameras, having a focal length about the diameter of the full 645 frame. They are slightly long on the 33x44 frame of the 645D and 645Z, making it a good short portrait lens for use with studio lights and outside fill flash. I bought this for the latter use case, as part of my 645NII wedding kit. The lens came from KEH over a dozen years ago, when I paid a little over $400 for it.
On the NII, this lens automatically sets the camera to LS mode, which automatically sets the shutter speed to 1/8. When using the leaf shutter, one had to meter manually (or use an automatic strobe), because the lens does not tell the camera what shutter speed is being used. Likewise, there is no A setting on the aperture ring. When using the focal-plane shutter in the camera, the leaf shutter is cocked and set to "o" for "open", at which point the lens operates with full wide-open metering and can use aperture-priority automatic exposure. Because there is no A setting on the aperture ring, shutter-priority automation is not available. The camera will automatically set the mode to Av even if the mode dial is pointing to some other setting, being M being the only allowable alternative.
But I found that the 645Z provides the same LS display, but for some reason does not set the 1/8 shutter speed. The focal-plane shutter duration has to be long enough so that the stop-down lever 1.) stops down the lens, 2.) triggers the leaf shutter cycle, which 3.) closes the leaf shutter right before the focal-plane shutter opens (and this is just a matter of designed timing--there is no mechanical interlock), then 4.) opens and closes the leaf shutter right after the focal-plane shutter opens (again, just a matter of timing--there is no interlock). The leaf shutter stays closed after the exposure, which is disconcerting for many but not for me. My experience with a range of SLR's of ancient design has taught me that instant-return mirrors are a modern luxury, not a human right. If the camera doesn't force the focal plane shutter to 1/8, it will often set the shutter speed automatically and that is usually too fast to ensure that the focal plane shutter is open when the leaf shutter fires. When that happens, one gets an image that looks like this:
I don't know why the 645Z does not operate the leaf shutter lenses as it should. The NII does it correctly, and it seems to me the 645Z firmware could do the same. Even though the camera reports "LS", the selected shutter speed is out of range--the EXIF reports "1/infinity s". It's nuts, but there it is. As has been reported here before, one must tape over the contacts on the lens (of which there are only a few) to prevent any electronic communication between the lens and the camera. Then, one must put the camera in M mode, and set the shutter speed to 1/8 second, at which point the leaf shutter will work as intended. To take a meter reading when using the leaf shutter, here's the process:
- Cock the shutter.
- Set the leaf shutter to "o", which opens the shutter for viewing.
- Set the focal plane shutter to the desired speed (which will be 60, 125, 250, or 500--the speeds provided by the leaf shutter).
- Adjust the ISO and aperture to center the metering display.
- Set the leaf shutter to the desired speed.
- Set the focal plane shutter in the camera to 1/8.
The idea was that one would not need to do this often, because one would only use the leaf shutter with flash, and the exposure would be dictated by the flash and not the meter. But when using fill flash, which is the primary use case, one must meter AND set the flash. I usually set the flash to expose a stop less than the ambient light (with an automatic flash, I set the ISO on the flash to twice that of the sensor, which will give it one stop less exposure), and then set the camera to ambient light. This requires metering the scene. Of course, one can also use an external meter.
So, in practice, the leaf shutter is cumbersome to use. But it's not any worse than it used to be with most commercial cameras--my Mamiya C3 didn't have a meter at all, let alone a fully coupled one, and the leaf shutter was the only option with that camera.
But the lens is fully usable with the focal plane shutter in the camera, with aperture-priority automatic exposure. This is not a spray-and-pray lens, but it works conveniently enough to serve as one's only 75mm prime, for those who have occasional use for synching a flash at speeds higher than 1/125. Note that the 645Z focal-plane shutter syncs with flash up to 1/125, so really only 1/250 and 1/500 leaf shutter speeds provide any real utility.
The flash we are talking about is NOT a Pentax P-TTL speedlight like the AF-540FGz. The flash sync interface is through a PC connector on the side of the lens, not through the hot shoe. This lens works best with an old-fashioned automatic flash like a Vivitar 283 mounted on a bracket that doesn't touch the hot-shoe contacts, or with studio strobes. For set shots (such as outdoor portraits), I would often set up studio lights at the site (I still have that Speedotron 1600ws Brown Line power head with two mains and two fills). The flash power would be set to be compatible with ambient lighting.
For those who never imagine themselves using the leaf shutter, get the A or FA 75mm lenses for the sake of convenience. It's a little like the old joke about the talking dog. A dog trainer comes to a talent agent, and says, "Book me at a circus, I have a talking dog." The talent agent says, "Okay, Fido, tell me what's over our heads." The dog says "woof!" The talent agent angrily kicks them out, and once outside, the dog looks at the trainer and says, "what was wong with that?" The trick is not that the dog speaks well, but that the dog speaks at all. The trick with this lens is not that the leaf shutter is easy to use, but that it's there at all on a camera fully optimized for a focal-plane shutter.
So, are optics worth all this palaver?
Pretty much.
In short, the optics are quite good, even by normal-prime standards.
Here's the full image, at f/11, using the 75mm LS:
Here's a 1:1 crop of the center at f/2.8:
It's sharp enough, but there's a bit of flare that reduces contrast and gives everything a bit of a glow. This is not a bug, but a feature. For a lens that is 1.3 times normal, and thus can serve as a short portrait lens (a useful use case for high-speed flash sync anyway), one wants a bit of softness at maximum aperture. Remember also that the 1:1 clip, when viewed at the 100 pixels/inch of typical monitors, is part of an image seven feet wide. The above is not bad.
For comparison, here's the DFA 55 at 2.8:
The 55 is a lens for making things sharp, not for making things soft, and it really doesn't do soft very well. The 75 can do both.
By f/5.6, though, it's as sharp as anyone would want. Here's a 1:1 clip at f/5.6:
Again, it's not as contrasty as the 55, but it's still quite sharp.
Here it is at f/11:
Which isn't really any sharper than f/5.6.
And at f/22:
Between f/5.6 and f/22, all that gets sharper is the out-of-focus foreground and background.
Again, here's a comparison with the 55 at f/11:
Differences are subtle, if we can barely see them at these magnifications.
So, center performance is excellent by f/5.6, but how does it do in the corners?
Upper right corner. 1:1 at f/2.8:
The leaves that are mostly in focus are also in the focus plane, being about the same distance from the camera as the lamp. No lateral color, not longitudinal chromatic aberration, no appreciable field curvature.
So, how does it compare with the 45-85 zoom, one lens that might keep me from needing this one on many occasions?
Here's the 45-85 at 65, in the center at a good aperture:
Hmmm. The 75 is good, but the zoom is just as sharp, and far more convenient. it's just not as fast. This one's on the bubble for an essential lens on a trip focusing on landscape photography, but for a gig that needs a lens that can do portraits that won't require a touch of softening in post, this one will do very well.
Rick "special-purpose lenses often get left behind even when they are good" Denney
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As before, these are straight out of the camera, processed in DxO Photolab with the driest possible settings.
One of the tests of a zoom is whether it's better to carry a range of primes. The only good prime that competes at this end of the zoom range is the DA or DFA 25mm lens, which is of course no longer in production. The only lens I have in my collection that hopes to compete at this focal length is an Arsat 30mm Fisheye. So, what the heck, let's show the center crop from that lens (which is itself also a beast). Here is the image made at f/11, so we are comparing the best aperture of that lens with the wide-open aperture of the 28-45.
The Arsat doesn't stand a chance. But if you need a fisheye, and only a fisheye will do, then the Arsat is one.
But the real test of a wide-angle lens is in the corners. Is there field curvature? Does the sharpness hold up in the corners? Let's look. Here's the lower right corner:
This isn't curvature--it's just loss of sharpness in the extreme corner at f/4.5. But this IS just the very corner--compare this with the full image above. We're talk the four or five inches from the corner on that seven-foot print. This loss of sharpness in the corner nearly completely cleans up at f/5.6, and we'll look at f/8 further down and see that the effect is completely resolved once we've stopped down a bit.
What about curvature: Here's the upper left corner:
The branches you see are about in the focus plane, and they are sharp. The loss of sharpness that would correspond to the lower right corner is suffused into the bit of house that is quite out of focus. I don't see evidence of curvature here.
And here's the lower left corner, which was generally sharp with the FA35 (which is known for curvature). The field looks acceptably flat at 28mm.
While we are at 28mm, let's look at several apertures and see if we can determine the ideal aperture. Here's the center again at f/5.6:
f/8:
f/11:
f/16:
And f/22:
There is no practical difference between f/4.5, 5.6, 8, and 11 in the center of the image and in the focus plane. F/16 starts to degrade slightly, though I may be imagining it, but not enough to keep me from using it even for a large print. F/22, though, would allow only a more subdued print size. But insufficient depth of field trumps diffraction.
Before moving away from 28mm, here's the lower right corner at f/8:
At f/8, it's sharp right to the corner.
F/5.6:
And at f/8:
Here is the FA 35/3.5 at f/11:
This makes me want to check that f/8 exposure, which is very slightly softer than the f/4.5 image. F/5.6 is the clear winner of all of these, but the 35 may be diffracting a touch at f/11. The 35mm prime is very good in the center, but it's not better than the zoom. It is a LOT cheaper, though.
Here is the upper left corner at f/8:
Again, no sign of field curvature. The branches and dead leaves are close to the focal plane. The wood at left is only five feet from the lens, and the background pines are three times as far as the focus plane. There is a touch of movement blur here--shutter speed was 1/13 second. The camera was, of course, mounted on a tripod, but that river birch tree will move in not much breeze.
Here's the 45-85 zoom at 45 and f/4.5:
The 45-85 is stunningly good, especially at the short end. The 28-45 is a bit better.
Here's the same comparison at f/8:
Again, the 45-85 is outstanding, and the 28-45 is a bit better.
Finally, a word about focus accuracy. This lens front-focused very slightly, and I set the focus adjustmentment for this one to -3.
In conclusion, a good example of the 28-45 is an amazing performer. I tested the failed lens for details about shake reduction, but I did not test again here. I find that shake reduction is good for about a stop, but I did not use it in the above images that were made on a tripod using mirror pre-release.
But these lenses are not bullet-proof. If you buy one pre-owned, 
And the 1:1 center crop, at f/4.5:
This is pretty soft. The bokeh is decent, but at f/4.5, it's hard to really paint the background with a wide, smooth brush.
Let's compare it to the 75 leaf shutter lens at f/5.6:
So, the 80-160 is better wide open on the short end than is the 45-85 wide open at the long end. Buf if you want a wide aperture, use a prime.
As with the shorter zoom, the 80-160 sharpens up very well at f/8:
It's still not as good as primes, or as the FA 45-85 at f/8, but this is a snip from the middle of what would be a seven-foot print at the usual monitor resolution of 100 pixels/inch. This is quite usable.
1:1 center crop at f/4.5:
Not too sharp. But let's look at it at f/8:
At 120mm, it's still getting sharper at f/8, but let's compare it to the 645 A 120 Macro, at f/8:
Again, the prime is better.
1:1 Center crop at f/4.5:
A little soft, but no worse than at shorter focal lengths. In fact, I think it's rather better than the short focal lengths. So much for the conventional wisdom.
1:1 center crop at f/8:
As with 120mm, it takes until f/8 to get all the way sharp, and that's the only weakness at the long end that I can see. Wide open, it has a soft-focus effect and reasonable bokeh, with a similar effect to the 165/2.8 Pentax 67 lens.
So, how does it play at the edges, wide open? Here's the lower right corner at 1:1 and f/4.5, and 160mm. The grasses are near the focal plane, so a severe curvature would show them softer than they are. The field is pretty flat. I see some coma, where the safittal performance is perhaps not quite as good as the tangential performance. This would sharpen up pretty nicely with some unsharp masking.
I don't see any lateral color, either, or longitudinal color, though the contrast might not be high enough here to reveal it.
Now, let's explore a different application. Usually, lenses of this length are thought of as portrait lenses, where we will often use selective focus to bring attention to the subject. But let's say our real objective is a landscape, where we want everything sharp. We are often most afraid of diffraction, but this is an unreasonable fear. Diffraction takes the edge off the stuff right in the focus plane, but it adds sharpness to the foreground and background, and can therefore often make an image look sharper.
Here's that center crop again at f/22:
The center is fractionally less sharp than at f/8, but everything else in the photo is sharper. Nothing is ever fully sharp if it isn't in the focal plane, but make a big print (let alone a small print) of the above and those background leaves will seem sharp.
Continuing the examination of f/22, let's look at the upper left corner, which shows foreground material, and the upper right corner, which reveals background material.
Upper left corner at 1:1 and f/22:
The leaves, which are close to the focal plane, are sharp. The bark isn't sharp at this magnification, but in a moderate print at normal viewing distance it will seem sharp enough, perhaps, and some judicious sharpening will also help.
Here's the upper right corner, with pine trees in the distant background:
Even this image, most of which depends on the depth of field, looks sharp. The bark of the River Birch at left is quite sharp, and the background is reasonably sharp. This lens can definitely make a 16x20 that never undermines the illusion of endless detail.
I had so much trouble trying to decide what the optimal aperture was, that I decided to show all of them.
I'm only showing center crops, simply because I could tell the difference between the centers and the corners. Okay, I'll show one corner. Here's the lower right corner at f/11 and 1:1:
There is some motion--this was a 1/3-second exposure. But the image is sharp. Remember, 1:1 at 100 pixels/inch of most monitors is part of a print seven feet wide.
So, back to the center. Here's the center of the frame at 1:1, shot at f/4:
Not too shabby, for sure. Sharper than the A* 300.
The bokeh isn't much to write home about, though, so I'm not thinking this is a superlative portrait lens. At wide apertures, you'll be adding gaussian blur to the image to make it tolerable for a portrait of a sitter who will actually expect the image to be flattering, but even at wide apertures, the background will be distracting. But that's not what this lens is for.
Here it is at f/5.6:
In the focus plane, I'm not absolutely sure I can tell these apart.
And at f/8:
Worse still.
F/16:
F/22:
It's bee a long time since I looked at an SLR lens that was actually at its best wide open. In fact, I'm not sure I ever have. This may be the first truly diffraction-limited medium-format lens I've ever handled. With this lens, you use the widest aperture that provides the necessary depth of field.
Let's look at that lower right corner again. Here's f/11 again:
Yup, even the corner is sharpest wide open, as long as it's in focus.
Simply amazing. Even the superb 55/2.8 got sharpened up enough down to f/11 to overcome diffraction.
Oh, you can bet this one's going to Alaska. This will be one of my most used lenses. Now, I have to wonder if this lens with the 1.4 converter will be sharper than the 200/4, which, stopped down a bit, is no slouch.
I'm going to have to adapt this lens to my Canon and put it up against my 70-200f/4L (which I think it will beat) and the 50mm Compact Macro, which is one of the sharpest lenses in the Canon line.
Rick "this one's dangerously sharp" Denney
And the 1:1 center crop, at f/4.5:
Nope, no chromatic aberration. DXO Photolab has this lens in its database, but there's no lateral color at f/8 even without those corrections. Also, the leaves that are sharp are at the focus plane, near enough, so there's not much field curvature.
Here's the lower corner, which is about half the distance to the focal plane:
Depth of field is decent at f/8 and 45mm. Remember, these are 1:1 crops--parts of images that would be 7 feet wide at the 100 pixels/inch of most monitors.
1:1 center crop at f/4.5:
Okay, this needs a smaller aperture.
1:1 center crop at f/8:
This lens really is soft at wide apertures and 85mm, so let's look at three apertures and watch it sharpen up by f/8:
1:1 Center crop at f/4.5:
1:1 center crop at f/8:
As with 65mm, it takes until f/8 to get all the way sharp, and that's the only weakness at the long end that I can see. Wide open, it's actually sort-of dreamy, with a soft-focus effect and very smooth bokeh. This would be a good portrait lens at the 85 end, though to be honest I've never used it at wider apertures. It has a similar effect to the 165/2.8 Pentax 67 lens.
Just for grins, here's a reminder of the 55/2.8 at 2.8:
And here is a crop from an image made with the 1.4 converter, downsampled to the same resolution as the image above:
No question: Downsampling the longer lens combination is not better than using the shorter lens. But considering these crops (at least the first one) is part of a 7-foot-wide print viewed at 100 pixels/inch, they are both really good. I'd use the 1.4 when I needed all fifty million of my pixels, but otherwise the A* 300 just has nowhere to go but down. It didn't go very far down here, but the converter still degraded the image more than enlargment.
Another question is whether a shorter lens plus a converter is better than carrying both the shorter and the longer lens.
Here is a 1:1 crop made using the 400/5.6 ED(IF), at f/11:
And here is a crop at 1:1 (without downsampling) from the 300+1.4 at f/11:
Not much difference here, but I would say that the 400 looks a bit better. Clearly, the A* 300 is a (slightly) better lens, but the 400 is worth bringing if one needs to optimize for that focal length.
So, the advice is: If you use the 1.4, start with a great lens. Stop it down a bit, and then 
Full scene at f/5.6
1:1 at f/5.6, not much loss compared to f/11
1:1 center crop, f/2.8:
1:1 center crop at f/4:
1:1 center crop at f/5.6:
1:1 center crop at f/11:
Rick "a steal at current prices" Denney