Astigmatism

I fell for Fujifilm recently. I loved 35 mm film photography in manual exposure mode, and somebody pointed out the X-T30 which operates much like my beloved Canon and Nikon full manual cameras. Having controls fall naturally to the hand is everything in a good camera. It’s nice that I could set both command dials to control ISO, which is a dial I never had to use while actually shooting on film. I haven’t tried the camera much in any automatic modes, except that I did do a series of test photos to analyze with RawDigger, sweeping through all the available ISO settings. I used aperture priority so the camera could select various odd shutter speeds, letting me keep aperture (and vignetting) constant throughout the experiment. Some of the things that have blown me away which I didn’t even know about when first getting into Fujifilm: the OIS is so good it’s scary, letting me handhold way longer and slower lens settings than I’d have imagined, like I’m temporarily pinning the image to the world. Autofocus is super nice and sharp, and it’s fantastic being able to touch the LCD screen to focus on a particular area anywhere in the image and fire off a shot. And the 50 mm f/1.0 shooting at f/1.0 is amazingly selective for the distance things are in focus, almost like dropping a curtain behind the subject. I bought a set of Fujinon XF prime lenses: 14 f/2.8 R 27 f/2.8 R WR 35 f/1.4 R 50 f/1.0 R WR 80 f/2.8 R LM OIS WR Macro And a couple Fujinon FX zoom lenses: 18-135 f/3.5-5.6 R LM OIS WR 100-400 f/4.5-5.6 R LM OIS WR Other Fujifilm gear: XF2X TC WR 2x Teleconverter X-T30 II Camera Body And a third party item: Meike 6.5 f/2.0 Circular Fisheye, a $129 barrel distortion of fun!

Wow, that's for sure. I crept downstairs last night and ordered the Fuji 100-400. All the same, there are some... interesting... options out there with T mounts. In the film days, I really enjoyed experiments with the lens off the camera, using other means (sometimes a separate lens of some sort and sometimes not) to create an image. On the down side, ruining the sensor would be a much bigger deal than ruining film. But on the up side, I could work incrementally and see what each photo looks like before taking the next.

I've heard the front of the sensor (X-Trans IV in my case) is glass, and that it is very fragile or pretty durable, and I think the manual says never touch with anything, but many 3rd parties sell little cleaners that look like a cross between a Q-Tip and a spatula. I've seen things about just scrubbing it with a dirty shirt, and similar, which I guess are jokes but it's never clear. How scratch resistant is it? And how strong, is it very thin like a microscope slide cover? The back illumination manufacturing process used to make it sounds like it would be thin. Thanks!

I've grown a nice set of Fuji XF prime lenses from 14 mm to the 80 mm macro, and have the 2X teleconverter too. But where are the primes in the neighborhood around 200 or 300 mm? In my 35 mm film photography days I had Canon equipment, almost all primes, including their 300 mm f/5.6. I loved that lens! It was a clean cylindrical shape with a built in hood that slid forward or back, which was very convenient and made it really easy to pack. That'd be similar to buying a 200 for my new X-T30 II. But they don't have Fujinon primes in this space. I have 160 when I use the teleconverter on the macro. There's not much point in buying the 90 mm prime as it's so close to the 80. And they have the 400/2, which I'd love to have, but it's way out of my price range. And nothing else between them. There's the 70-300 zoom, which I guess I'll get when I can (they seem hard to find though I have watches set at a couple stores). I'd have preferred a prime, though. I do own one zoom, the 18-135, for "one size fits all" needs, and its long end is worth having. And, there's the 100-400 zoom. If I got into the right mood, I'd order that, but it'd be kind of irresponsible for me to pay nearly $2k for it. I did order a cheap Tokina manual catadioptric lens, 400 mm, $250, to get a top end that reaches way out there, though it will probably be a bit of work to focus it well. It was supposed to arrive yesterday but is running late. We will see. I've never had an autofocusing interchangeable lens camera before, and I really like how accurately and quickly the camera does it, so an autofocusing lens would be nice. Surprisingly, 3rd parties hardly offer anything prime in this range, either. What can we hope for?

This is an old thread, I know, but I bought this 50 mm f/1.0 lens recently. It's pretty amazing. Cost a lot, though!

More on inkjet photo printing: lots of online references say they can deliver around 7 or 8 stops of dynamic range. Here are two discussions with lots of details: https://forum.luminous-landscape.com/index.php?topic=44370.0 https://www.dpreview.com/forums/thread/2254402 For a long time I've daydreamed about a printing method to get very high dynamic range: print transparencies, one backwards, and laminate them together with careful alignment. Then illuminate them from behind with a bright light, maybe uncomfortably bright in the smallest highest highlights. I've also thought about making that bright light from three nearly monochromatic light sources chosen to increase the color gamut of the printing ink (you could certainly increase the gamut by filtering out the wavelengths that contribute least to color distinction).

I appreciate your post! Thank you! This is all fascinating, including the white paper. I also get the idea that on this sensor an ISO setting of 800 is a locally sweet spot -- that is, there seems little reason to pick 640, as it is a local "sour spot". My impression is that "ISO invariance" amounts to a claim that the sensor has much more range than jpg files or monitors do, so that users can choose their ISO setting by whatever criteria they like without any image degradation. Maybe more than inkjet photo printing too, I mean to look that up. "ISO invariance" doesn't seem to be a specific technical feature, though. Is it?

Great answer jerryy! Thank you! I've wondered about several of the charts there on photonstophotos. Several of the charts show a sudden change between ISO 640 and 800. In particular the "Input-referred Read Noise versus ISO Setting" chart, in the first link below, has a step there that is overwhelming compared to the range of data nearly everywhere else. I don't know what to make of them. Maybe there's a shift between two different A/D amplifiers each of which has multiple gains, maybe there's also a digital change introduced there. I've tried to make sense of this by looking at RawDigger histograms (which are fascinating in several ways) -- do they start to have a pattern of empty bins? Or what they call "pits", nearly empty bins? Any thoughts on this? https://www.photonstophotos.net/Charts/RN_e.htm https://www.photonstophotos.net/Charts/RN_ADU.htm

As indicated how, the "L" that appears on the settings below that? Does Fuji say "artificial" somewhere?

I have a new X-T30 II and am learning about it. One mystery is the base ISO of the X-Trans 3 Sensor. I haven't anyplace in a reference from Fujifilm, including my user manual, that says. I also haven't noticed anything at PhotonsToPhotos, or in my RawDigger software, either. But there are many online references that say, and they seem equally split between 160 and 200, with a few scattered oddballs like 640 or 800 or 1000. FWIW, I think the working definition of "base ISO" would be "the ISO setting that puts the metering point at 18% (or 12%) of full scale in the green channel when metering off of an 18% gray card, while simultaneously causing a 100% white Lambertian reflectivity card next to the gray card to give raw pixel values of 2^14 in the green channel, and just saturating the sensor wells (i.e. onset of clipping by the wells)." What I have been able to find doesn't even make it clear that there is a literal definition of "base ISO" from the International Standards Organization themselves. What do you think? Thank you!!

I've just had the best time trying to understand what the ISO setting does in my new X-T30 II. ISO numbers are modeled after the old ASA numbers for film, and films were truly different to create their speeds (I was a big fan of Kodak Pan, Plus and Tri X at ASA 32, 125 and 400 IIRC). But I find references online, in the manual, and in books, that seem to confuse all this. So I bought RawDigger, which is software that reads RAW files including the ones my camera writes, and lets you do statistics on the pixels. Below is the table of data I generated. Filename is just the photo name, Sample_Name describes the central 600X400 pixel rectangle I did my measurements in, Shutter is the Shutter_Value reported in the EXIF (there's a rounded version of that that is more accessible but apparently less accurate), and for Red, Green and Blue we have an average and a standard deviation. This made it clear that the camera is writing 14 bit pixel values. I took this series of photos with the Fujinon 80 mm macro lens at f/2.8, in aperture priority mode, letting the camera adjust the shutter speed to make my exposures "right" at every ISO. By "right" they seem to mean about a 14% or 16% gray, at least in the green channel which is the one I paid the most attention to. I had the camera on a tripod with the lens a few inches from a sheet of paper, but the lens was manually focused at infinity to blur any texture in the paper. The paper was taped to the inside of our downstairs sliding glass door where it was backlit by our gray day (which wouldn't have any flicker like our indoor lighting would), and I worked quickly so the light wouldn't change much. I kept shifting the ISO and taking a picture. Filename Id Sample_Name ISO Shutter Ravg Rdev Gavg Gdev Bavg Bdev DSCF0190.raf 1 2823:1885-600x400 80 0.023810 2216.86 37.914 4618.88 57.640 3319.76 47.421 DSCF0191.raf 1 2823:1885-600x400 100 0.019231 2235.03 42.159 4653.14 63.400 3344.33 52.997 DSCF0192.raf 1 2823:1885-600x400 125 0.014286 2207.49 46.383 4595.81 69.240 3302.66 57.713 DSCF0193.raf 1 2823:1885-600x400 160 0.011765 1107.19 25.931 2301.03 37.817 1654.98 31.877 DSCF0194.raf 1 2823:1885-600x400 200 0.009091 1107.62 29.042 2302.50 41.715 1656.32 35.520 DSCF0195.raf 1 2823:1885-600x400 250 0.007143 1104.86 32.353 2297.14 46.321 1652.51 39.415 DSCF0196.raf 1 2823:1885-600x400 320 0.005882 1108.27 36.223 2305.09 51.731 1659.00 44.053 DSCF0197.raf 1 2823:1885-600x400 400 0.004545 1105.60 40.168 2300.77 57.615 1655.81 49.440 DSCF0198.raf 1 2823:1885-600x400 500 0.003571 1100.87 45.328 2303.92 64.488 1655.62 55.007 DSCF0199.raf 1 2823:1885-600x400 640 0.002941 1106.97 50.532 2319.02 72.443 1668.62 61.623 DSCF0200.raf 1 2823:1885-600x400 800 0.002381 1102.26 56.709 2310.84 80.642 1663.07 69.028 DSCF0201.raf 1 2823:1885-600x400 1000 0.002000 1115.02 63.675 2338.81 90.478 1684.51 78.111 DSCF0202.raf 1 2823:1885-600x400 1250 0.001471 1103.31 70.903 2315.34 100.94 1666.91 86.671 DSCF0203.raf 1 2823:1885-600x400 1600 0.001176 1103.12 79.595 2315.34 113.06 1668.75 97.235 DSCF0204.raf 1 2823:1885-600x400 2000 0.001000 1137.55 91.134 2390.45 128.58 1722.92 110.99 DSCF0205.raf 1 2823:1885-600x400 2500 0.000714 1132.56 101.96 2378.89 144.38 1713.78 124.72 DSCF0206.raf 1 2823:1885-600x400 3200 0.000588 1152.40 115.72 2419.68 162.58 1740.69 140.23 DSCF0207.raf 1 2823:1885-600x400 4000 0.000455 1154.66 129.77 2421.64 183.12 1741.71 157.47 DSCF0208.raf 1 2823:1885-600x400 5000 0.000370 1145.31 146.93 2399.44 205.13 1723.30 177.25 DSCF0209.raf 1 2823:1885-600x400 6400 0.000312 1152.15 163.63 2413.90 229.57 1729.91 199.96 DSCF0210.raf 1 2823:1885-600x400 8000 0.000227 1198.36 190.44 2532.11 272.33 1806.28 233.41 DSCF0212.raf 1 2823:1885-600x400 10000 0.000185 1167.54 214.59 2465.34 303.63 1755.25 259.34 DSCF0213.raf 1 2823:1885-600x400 12800 0.000143 1203.58 244.62 2535.27 343.70 1800.83 294.57 DSCF0214.raf 1 2823:1885-600x400 25600 0.000071 774.31 236.88 1594.28 295.63 1159.30 279.98 DSCF0215.raf 1 2823:1885-600x400 51200 0.000036 411.89 177.73 838.00 220.37 614.93 210.30 Here's what I learned: If by "sensor" we mean the sensor chip that includes analog to digital conversion, then over most of its range the ISO setting does change the sensitivity of the sensor by changing the analog amplification before the digitization. This, coupled with the changing automatic shutter speed (which was either mechanical or electronic at different speeds), kept the raw pixel values at around 14% or 15% of the full scale 2^14. At ISO 80, 100, and 125, which are all specially preceded by an "L" in the display, there's something else going on that I haven't figured out, but it would have overexposed areas that were just 2 stops brighter than my sample area, so not much headroom for typical photography. At ISO 25600 and 51200, which are both specially preceded by an "H" in the display, the exposure fell way off, and I think for ISO 12800 the analog amplifier must have already been at maximum gain, so all they could do is encode someplace that the jpg conversion should bump up the brightness for the two highest ISO settings. Note that over most of the range, ISO numbers go up by around 1.25X per step, but these last two are going up 2X. It is interesting to see that the noise, or at least the standard deviation as a fraction of the average as a proxy, goes up steadily. In those last couple steps this standard deviation over the mean goes way up. I might be able to clean this up with a more constant light source (which of course must not flicker), and maybe a frosted glass filter threaded into the front of the lens so there's less texture. All the same, I feel now like I know how to use the ISO -- whereas all the references I had left me nearly clueless what to do.

I got the 6.5 Meike recently and it's a blast, for $129 a whole lot of fun. The images look quite sharp to me. I have to greatly enlarge the very edge to see blur and a little chromatic aberration. I'm quite happy with it. It covers slightly more than 180 degrees. Based on a review I saw on Amazon, it seems somebody else got caught by the same problem I had. There's a setting in the camera that enables shooting without a lens, and until I turned this on, I could see through this lens with the viewfinder but the shutter would not fire. It's a manual lens, which means among other things my X-T30 II does not seem to recognize it as a lens. I was worried it was defective, but found mention of this on Meike's web site, and it fixes all. The setting to enable shooting without a lens does not seem to do any harm when shooting with Fujinon lenses, so I've just left it on.