Film scanning with Sony mirrorless and Adobe Camera Raw

I’ve been shooting film for a few years now, and scanning/digitizing it myself almost as long. Here’s a guide to how I do it. This is mostly for slide film but should apply to any types of film.


Needed equipment


You’ll need to start by setting your camera at the right distance from the film. Point it at the film and raise/lower the tripod until it fills the frame. For 6x6 like I have here it will be square, for 135 it should fill the whole frame. Since this is approximate you can leave the film in the sleeve. If you can turn on grid lines on your PC app this can help here. Your film should go between the light pad and the dark mask.

Setting up for distance

View for distance in the camera app


To make sure everything is in focus, you need to have your camera perfectly parallel to the film. An easy trick for this is what the mirror is for. Place the mirror on your light pad and align your camera so the reflection of the lens is exactly centered. A grid helps here too. You may need to do several iterations of distance and centering to get everything perfect. Once it’s set up though you don’t need to touch it unless you change film formats (e.g. 135 to 120).

alignment setup


White balance

You’ll need to calibrate your camera for the backlight you’re using. Take your film out and shoot a picture of just the backlight.


Here I’ve placed several color samplers across the diagonal. Set the white balance temperature and tint so the red, green, and blue are equal (pure white). Also set your lens corrections so the lens falloff is compensated for (brightness is equal across the frame). Depending on your lens you may not able to fully compensate for the falloff. You can also do this by looking at the color histogram in the upper right, get the peak as narrow as possible and eliminate the color fringes.

Exposure settings

Put your film in, and hold it down with the mask and whatever you’re using for weight.

Your setup probably looks something like this:


For exposure settings, use the lowest base ISO your camera supports (probably ISO 100). Avoid any trick ‘pulled’ ISOs.

When it comes to aperture, shoot several test shots and see what looks best. You’ll have to balance sharper apertures with diffraction softness. Here’s a spread at f/2.8, f/4, f/5.6, etc. from the center of the frame.


It’s hard to say but either f/5.6 or f/8 looks the best, here’s the corner:


I think f/5.6 looks the best so let’s pick that aperture.

For shutter speed it’s a bit of artistic choice. I compared what I saw on the monitor to what the slide looked like on the light pad. It will also depend on the particular photo as you can compensate for over/under exposure in the scanning process.

I ended up using f/5.6 at 1/6 ISO 100 for 6x6 Fujifilm Velvia 50. Don’t forget that you will have to change the exposure for different formats as macro lenses get darker when focused to close distances.

Mess with the exposure slider in Camera Raw then set that difference on the shutter speed on the camera.

Camera Raw settings

This is also a bit of artistic choice but I found leaving everything as neutral as possible looked the best. Set all the sliders to zero as a base setting, and save that as a preset.


For image settings, generally you want to leave it at the base camera resolution. I turn it down a notch when scanning grainy film like Kodak Tri-X 35mm because the extra pixels aren’t getting you any more resolution.

To save disk space and processing time I usually leave it at 8-bit sRGB, you may want to set it to 16-bit if you take it straight into Photoshop and expect to do some heavy editing. Don’t use Adobe RGB or any other color spaces unless you can control everything all the way up to printing because any slip-up and your colors will look like crap.

You can also crop it here to square or whatever other format you may be shooting.


Really the only tweak I do in Camera Raw is the recovery slider. It will recover blown highlights that are overloading channels. Notice that the bright highlights on the hut are starting to turn glaring yellow and look like pizza cheese or something. There is also a colored triangle in the upper right of the histogram to let you know the highlights are overloaded.


Add a bit on the recovery slider to fix these highlights. Don’t use too much or your picture may end up looking dull and flat. If you find yourself adding too much, speed up the shutter speed on your camera to reduce the exposure and try the scan again, instead of trying to fix it in Camera Raw.


B&W negative

This guide has been for color slide film, which is probably the easiest to scan even though it has a reputation for being hard to shoot. For black and white negative the process is the same except you will need to reduce your exposure as B&W negative is much ‘thinner’. You can also do the inversion here by going to the curves tab. Flip the end points to the opposite side to invert it. You probably also want to add a curve to make things look more natural, here’s a sample of a curve I used.


This is also artistic choice so play around with it until you get something you like. Since negative film is much more forgiving of misexposure you’ll probably need to tweak the curve for each shot.

Color negative

I have shot very little color negative. You can scan it this way too, but you will need to do the color inversion yourself. Photoshop has some curves presets for this, but I found it pretty difficult. I know there are programs out there dedicated to the color negative inversion process. You might try them out but I have no advice there since I’ve never used them.

Lab scans

I used to have my film lab scan all my slides. They were fine, but I didn’t like the lack of control over how it looked (unless I took my film back to the lab for rescanning). If you decide to use lab scans with slide film, at least ask them to not do any color correction. If you’re shooting with filters they’ll probably color correct the filters right out!

It’s much more of a pain but I’ve found the advantages of home scanning to be:


So here’s a comparison between a lab scan and a home scan of the same slide.



Home scan


Your opinion may vary but while the lab scan has better resolution and is sharper, the home scan is properly aligned, has better shadow detail, better color, and doesn’t crop off the edges.

35mm home scan

All the previous scans have been for 120 medium format film, if you want to see what kind of resolution you can get, here’s a full unedited scan of 135 Fujifilm Provia 100F at 24 megapixels:

Provia 100F example scan

Happy scanning!

Optimizing NVMe performance with dm-crypt

I recently switched over from Windows 7 to Debian Linux on my main desktop, and along the way decided to set up full disk encryption with dm-crypt because it seemed like support was good, so why not? At the very least it would save me any worry if the drive dies and I had to throw it out. In general I would like to have ‘performance’ more than ‘paranoid’ settings when it comes to tweaks. I basically accepted Debian’s default options on the install and went for it. I also ended up doing dm-crypt-on-LVM for the flexibility of multiple partitions. The drive ended up looking like this:

nvme0n1                               259:0    0  1.8T  0 disk  
├─nvme0n1p1                           259:1    0  512M  0 part  /boot/efi
├─nvme0n1p2                           259:2    0  488M  0 part  /boot
└─nvme0n1p3                           259:3    0  1.8T  0 part  
  └─nvme1n1p3_crypt                   254:1    0  1.8T  0 crypt  
    ├─m2-root                         254:3    0   32G  0 lvm   /
    ├─m2-swap                         254:6    0   32G  0 lvm   [SWAP]
    └─m2-home                         254:7    0  1.5T  0 lvm   /home

The problem came when I started running IO-heavy workloads, generally loading large AI models from disk. These only ran at about 1000 MB/s, far short of the 7450 MB/s they promise on the box. I know Samsung probably lies on these benchmarks but not that bad. Unfortunately I can’t remember what I got when testing under Windows 7.

I turned on all the performance options in /etc/crypttab, so the line for the NVMe ends up looking like:

nvme1n1p3_crypt UUID=21d6f689-0bcf-4c4e-ae81-0181c74bcd2f none luks,discard,no-read-workqueue,no-write-workqueue

Again, no saved benchmarks there but there wasn’t a noticeable improvement. Here’s what they looked like afterwards (from kdiskmark, 1 GiB test):

Sequential   1 MiB (Q=  8, T= 1):  7096.145 MB/s [   6929.8 IOPS] <  1145.94 us>
Sequential   1 MiB (Q=  1, T= 1):  1130.209 MB/s [   1103.7 IOPS] <   905.32 us>
    Random   4 KiB (Q= 32, T= 1):   734.142 MB/s [ 183535.6 IOPS] <   173.98 us>
    Random   4 KiB (Q=  1, T= 1):    78.616 MB/s [  19654.2 IOPS] <    50.46 us>

Sequential   1 MiB (Q=  8, T= 1):  1299.046 MB/s [   1268.6 IOPS] <  6146.53 us>
Sequential   1 MiB (Q=  1, T= 1):  1093.343 MB/s [   1067.7 IOPS] <   854.56 us>
    Random   4 KiB (Q= 32, T= 1):   413.172 MB/s [ 103293.0 IOPS] <   308.34 us>
    Random   4 KiB (Q=  1, T= 1):   210.846 MB/s [  52711.6 IOPS] <    18.76 us>

Note that the queue depth 8 sequential test actually comes pretty close to the advertised speed, but the Q=1 test is more like what I was seeing when running actual large loads from disk.

For comparison I ran a (256 MiB) test on the /boot partition, which is outside the dm-crypt volume:

Sequential   1 MiB (Q=  8, T= 1):  6863.149 MB/s [   6702.3 IOPS] <  1164.45 us>
Sequential   1 MiB (Q=  1, T= 1):  3559.749 MB/s [   3476.3 IOPS] <   285.60 us>
    Random   4 KiB (Q= 32, T= 1):   971.108 MB/s [ 242777.2 IOPS] <   131.33 us>
    Random   4 KiB (Q=  1, T= 1):    66.923 MB/s [  16730.9 IOPS] <    59.35 us>

Sequential   1 MiB (Q=  8, T= 1):  4557.689 MB/s [   4450.9 IOPS] <  1631.63 us>
Sequential   1 MiB (Q=  1, T= 1):  2848.125 MB/s [   2781.4 IOPS] <   250.41 us>
    Random   4 KiB (Q= 32, T= 1):   280.971 MB/s [  70242.7 IOPS] <   453.73 us>
    Random   4 KiB (Q=  1, T= 1):   264.417 MB/s [  66104.4 IOPS] <    14.64 us>

The read speeds are mostly the same, except that important sequential Q=1 benchmark is over 3 times faster! I did a bit of looking around, CloudFlare had a good writeup on optimizing disk encryption speed, and I also found this useful Reddit post. It seems like the sector size dm-crypt is using is important. It may be using 512 bytes, even though the overlying file system (ext4 in this case) is using 4096 so we never use any less than that size. Let’s check what size nvme1n1p3_crypt is using:

# cryptsetup luksDump /dev/nvme0n1p3
Data segments:
  0: crypt
    offset: 16777216 [bytes]
    length: (whole device)
    cipher: aes-xts-plain64
    sector: 512 [bytes]

  0: luks2
    Key:        512 bits
    Priority:   normal
    Cipher:     aes-xts-plain64
    Cipher key: 512 bits

We’re using a sector size of 512. It’s also using AES-256, in XTS mode (which is why the key is 2x the size).

I set up a test using my secondary NVMe. This is older and slower (Samsung 980 Pro vs the 990), as well as in the 2nd M.2 slot which means it’s sharing 4 PCIe lanes with the network interfaces, SATA devices, etc. instead of its own dedicated 4 lanes to the CPU.

I formatted this guy up, using the above options, but AES-128 to see if there was any appreciable difference. This is the sequence of commands. Note I’m reading the password from a file (which itself is on the encrypted /home drive).

# cryptsetup luksFormat --key-size=256 /dev/mapper/nvme1n1p2 < /my/password/file
# cryptsetup open /dev/nvme1n1p2 test_crypt < /my/password/file
# cryptsetup refresh --perf-no_read_workqueue --perf-no_write_workqueue --allow-discards temp_crypt
# mkfs.ext4 /dev/mapper/test_crypt
# mount /dev/mapper/test_crypt /mnt/test/


Sequential   1 MiB (Q=  1, T= 1):  1126.740 MB/s [   1100.3 IOPS] <   908.13 us>

A little faster, maybe from the smaller key size, but largely the same as above. Let’s try reformatting it with a block size of 4096 using the --sector-size=4096 option when calling cryptsetup luksFormat. Results:

Sequential   1 MiB (Q=  1, T= 1):  1994.320 MB/s [   1947.6 IOPS] <   512.92 us>

Nearly a 2x speed-up versus the original case! Obviously this is the way to go. For experimentation I tried a sector size of 4096, but with AES-256 to see how much of an effect that has:

Sequential   1 MiB (Q=  1, T= 1):  1768.740 MB/s [   1727.3 IOPS] <   586.19 us>

A little slower, but still faster with the larger sector size.

So, let’s change the key size and sector size. Thanks to the wonderful cryptsetup, we can actually do this online, on the boot drive, while using it! It even tolerates interruptions (not that I wanted to test this, it’s scary…). The command we want:

# cryptsetup reencrypt --key-size=256 --sector-size=4096 /dev/nvme0n1p3
Enter passphrase for key slot 0: 
Auto-detected active dm device 'nvme1n1p3_crypt' for data device /dev/nvme0n1p3.
Finished, time 51m22s, 1862 GiB written, speed 618.6 MiB/s

After an fstrim, a reboot, we end up with:

Sequential   1 MiB (Q=  8, T= 1):  7251.646 MB/s [   7081.7 IOPS] <  1121.95 us>
Sequential   1 MiB (Q=  1, T= 1):  1975.299 MB/s [   1929.0 IOPS] <   519.47 us>
    Random   4 KiB (Q= 32, T= 1):   743.511 MB/s [ 185877.8 IOPS] <   171.88 us>
    Random   4 KiB (Q=  1, T= 1):    84.115 MB/s [  21028.8 IOPS] <    47.20 us>

Sequential   1 MiB (Q=  8, T= 1):  3065.347 MB/s [   2993.5 IOPS] <  2532.55 us>
Sequential   1 MiB (Q=  1, T= 1):  2050.924 MB/s [   2002.9 IOPS] <   413.80 us>
    Random   4 KiB (Q= 32, T= 1):   477.777 MB/s [ 119444.3 IOPS] <   266.06 us>
    Random   4 KiB (Q=  1, T= 1):   244.687 MB/s [  61171.9 IOPS] <    15.65 us>

Alright so not quite double, but an improvement all around, for free! Write performance was also greatly increased. Still short of the unencrypted performance, but still pretty quick.

In summary, if you’re using NVMe drives with dm-crypt, for max performance I would:

The security implications of the above are left as an exercise for the reader, but personally I’m OK with it.