Some months ago Fujifilm released a printer driver for the Instax Link WIDE printer. I got interested as a way to print to a chemical photograph a digital image. Instax film is not particularly big, but with its approx. 6 x 10 cm image size, the Instax WIDE is acceptable.
When I did the first tests however I noticed that even with the PC/Mac driver, and not just with the app for iOS and Android, getting an accurate framing was hard, i.e. despite having the correct proportions, the image I sent to the printer was cropped a little bit.
So I started investigating what actual image size in pixels the printer supports. I found out that the answer is not trivial. This post is to share my findings with anyone who may have the same questions in the future.
According to the specifications, the native image size is 800x1260 dots with a resolution of 12.5 dots/mm (318 dpi, 80 μm dot pitch) producing an image of 62 x 99 mm.
If you do the math, these numbers are not 100% exactly consistent. If we take the 800x1260 size in dots and the 12.5 dots/mm as exact, then we get an image size of 64 x 100.8 mm. This would explain the little crop on all sides that I was obtaining when sending my 800x1260 image, as the image area is just 62 x 99 mm. And this would correspond to a "bleed" of 1 mm per side, which is a common practice in printing to ensure that the image fills a page with no white margins.
Now, if we apply the 12.5 dots/mm resolution to the image size of 62 x 99 mm of an Instax Wide film, we get 775 x 1238 pixels. So in Photoshop I created an image of 800x1260, with white margins of 12 pixels per side, and bingo, I got the full image printed.
The specifications mention that the supported image formats are JPEG, PNG, HEIF, DNG. This made me think that some conversion to a format supported by the printer firmware was occurring, and motivated the quest for what this format could be, so that I could send to the printer something that would not be processed in any way.
Inspired by the discussion at https://github.com/jpwsutton/instax_api/issues/21 I sniffed bluetooth communication between the computer and the printer, and found that what is sent by the driver is a JFIF file of 840x1260 pixels! So regardless of the size or format of the image you pass to the driver, it does some conversion before sending it to the printer.
The only way to send a truly unprocessed file (I mean, doing all the editing and resampling in Photoshop upfront, and then sending an exact byte by byte copy of that file to the printer) was to write my own "driver".
So I completed the reverse engineering of the BLE communication and wrote a Python command line program that allows you to send a JPG file with height 840 pixels, width 1260 pixels and maximum size 337920 KB byte by byte (remember that the visible area is just 775 x 1238 pixels, so you have to leave white margins). You can find it at https://github.com/paorin/InstaxLink
Since I have an old Mac that doesn't even have BLE, I also reverse engineered the communication with Bluetooth Classic, which is used when connecting with an Android phone, and implemented it in the same program.
So the program I share also allows you to print to an Instax Link from computers not supported by the official Fujifilm driver.
Enjoy!
When I did the first tests however I noticed that even with the PC/Mac driver, and not just with the app for iOS and Android, getting an accurate framing was hard, i.e. despite having the correct proportions, the image I sent to the printer was cropped a little bit.
So I started investigating what actual image size in pixels the printer supports. I found out that the answer is not trivial. This post is to share my findings with anyone who may have the same questions in the future.
According to the specifications, the native image size is 800x1260 dots with a resolution of 12.5 dots/mm (318 dpi, 80 μm dot pitch) producing an image of 62 x 99 mm.
If you do the math, these numbers are not 100% exactly consistent. If we take the 800x1260 size in dots and the 12.5 dots/mm as exact, then we get an image size of 64 x 100.8 mm. This would explain the little crop on all sides that I was obtaining when sending my 800x1260 image, as the image area is just 62 x 99 mm. And this would correspond to a "bleed" of 1 mm per side, which is a common practice in printing to ensure that the image fills a page with no white margins.
Now, if we apply the 12.5 dots/mm resolution to the image size of 62 x 99 mm of an Instax Wide film, we get 775 x 1238 pixels. So in Photoshop I created an image of 800x1260, with white margins of 12 pixels per side, and bingo, I got the full image printed.
The specifications mention that the supported image formats are JPEG, PNG, HEIF, DNG. This made me think that some conversion to a format supported by the printer firmware was occurring, and motivated the quest for what this format could be, so that I could send to the printer something that would not be processed in any way.
Inspired by the discussion at https://github.com/jpwsutton/instax_api/issues/21 I sniffed bluetooth communication between the computer and the printer, and found that what is sent by the driver is a JFIF file of 840x1260 pixels! So regardless of the size or format of the image you pass to the driver, it does some conversion before sending it to the printer.
The only way to send a truly unprocessed file (I mean, doing all the editing and resampling in Photoshop upfront, and then sending an exact byte by byte copy of that file to the printer) was to write my own "driver".
So I completed the reverse engineering of the BLE communication and wrote a Python command line program that allows you to send a JPG file with height 840 pixels, width 1260 pixels and maximum size 337920 KB byte by byte (remember that the visible area is just 775 x 1238 pixels, so you have to leave white margins). You can find it at https://github.com/paorin/InstaxLink
Since I have an old Mac that doesn't even have BLE, I also reverse engineered the communication with Bluetooth Classic, which is used when connecting with an Android phone, and implemented it in the same program.
So the program I share also allows you to print to an Instax Link from computers not supported by the official Fujifilm driver.
Enjoy!
