Instax - Scanning

This is a quick walk through with examples of my experience with scanning Instax film.

The idea is to cover what I have found that works, and what the expected quality would be.

I also intend to provide very high-resolution crops of the results to give a sense on the limits of the process as online most examples are very low resolution and don't provide enough detail.

Background:

Instax film is an affordable and reasonably high-quality instant film. The colors tend to be vibrant with good contrast.

But looking at the Instax datasheet [1], we can see a few initial issues. A very generous read of the exposure response curves gives a range of around 2 Log 10. Or about 100:1 Giving us a usable range of 6-7 stops depending where you place your end on the curve.

Having shot the film, I would say 6 stops about as good as you can expect.

This makes it more difficult to expose then even slide film. You really do need to nail exposure for a quality image.

The next issue is the film is highly reflective which always makes it a little trickier to scan.

The last piece is that the resolution figure (I will assume low contrast and not high contrast) is about 10 lines per millimeter.

For Instax square which I am shooting, we can expect the 62x62mm image to have decently resolved detail at about 620x620 pixels. As it's best practice to shoot at twice the target resolution for Nyquist, a 1200x1200px scan likely extracts everything in the images.

I will be scanning with a 48mp digital camera giving us many times more information from the scans then we should expect and sharing some 1:1 crops to let details be evaluated, and plenty of detailed scans of real photos.

The Setup:

Using the same general film scanning setup, some modifications have been done to make reflective style scans of images. As the Instax film is not much larger than a medium format frame, this works well for me.

This does mean we need a quality light source positioned to at the correct angle to avoid reflections into the lens.

The other challenge is that the film does not like to be flat. The top and bottom of the Instax film is slightly thicker than the middle. This gives a slight bowing. In a flatbed setup this shouldn't be an issue, but for the camera setup, it can provide focus variation that can be troublesome.

The lighting:

To get even lighting, using a flash or light that is approx. 45 degrees from the work should prevent reflection. A pair of white boards are placed on the opposite side for some fill. The reason being to maintain a slight bias, so the bottom of the Instax print maintains a darker edge.

Setup: Negative Under glass with a single light and bounce cards

I've been adjusting the setup and placement to reduce additional reflections, but the current setup is the above. I'll update with any improvements.

The biggest issue is still very dark prints can show additional reflections from other surfaces in the room. So increased distances from any walls or objects helps. But for most prints there have been no issues.

Using Glass:

A common trick to fix flatness issues is to lay a piece of glass over the work piece. The problem with this is there is a phenomenon of newton rings. Colored artifacts that happen when two glossy surfaces touch.

There is special glass that handles this called Anti-Newton-Ring Glass. The way this glass works is it has a chemically etched side to make it microscopically rough, preventing it from touching the surface of the work piece in a way to cause the rings.

It's quite expensive and difficult to acquire. But there are alternative options.

Instead of investing in ANR glass of the needed size for this scan, I have a piece of anti-glare framing glass. [2]

I do suspect that the texture of the glass shows up in the very high-resolution scans.

But we can also shoot without any glass at all. If we carefully try to focus the image on a very flat piece of instant film, we can then evaluate.

The difference in terms of any details actually resolved is pretty minimal. The largest difference is that the anti-glare glass seems to add a very subtle texture that gets exaggerated with sharpening.

But as it makes it much faster to get flat scans that are sharp, it seems worth the trade-off.

1:1 Crops of 2000x2000 pixels of the above images are provided. This should be enough to see the level of detail and difference between the method.

No Glass - No Sharpening - Glass

I do have a piece of "ANR" acrylic to use to compare:

Which also likely exceeds the level of detail needed, but the texture is even more apparent than the inexpensive anti-glare glass.

Note: The test images are a photo of a Macbook Air Display at 2880x1864. Aliasing artifacts are from the display. But the pixels on the display are not rendered at all. This works out to a pixel resolution of 34 lines per mm. About 3 times the films rated resolution.

Editing:

One thing is that without any editing the results are very soft looking. From some advice online and experimenting, I've found a certain amount of aggressive sharpening and disabling noise reduction gives better, film like results.

You can see the difference here.

No Glass - Aggressive Sharpening - Glass

One big disadvantage is that if you use glass to flatten the image, you need to check for dust. It can build and stick to the glass and needs to be cleaned as editing out the dust is tedious.

While I do not have a V750 Pro flatbed anymore or similar, we can take a typical flatbed scanner and test at its highest optical resolution.

No Sharpening - Sharpening

And a 1:1 crop at 2400dpi

No Sharpening - Sharpening

I think it is clear there isn't 2400dpi of resolution in these images which is why I didn't post the 4800dpi crops. At 95lines per mm, we are almost 10x the spec'd resolution of the film.

The No glass and Glass examples both seem to provide better results than the flatbed scanner. I will include a couple flatbed scans for comparison in the samples section.

Dust:

One aspect of Instax I wasn't expecting is how much of a Dust Magnet it appears to be.

While Dust with film is always an issue, cleaning the dust off the Instax film is a pain.

Because of this, there needs to be a dust removal step. If you have Photoshop the Dust & Scratches works well enough.

Otherwise this process is very tedious, and a flatbed scanner with dust removal might be worth using for that aspect alone.

Final Summary:

The impact of the glass in the scanning sometimes gives a slight sharpening effect that is smaller than the effective resolution of the film. I think it's a worthwhile trade-off to improve scan quality in terms of flatness and speed.

The max resolution does appear to not need more then 1200x1200 for the image area. As we want the border as well this means 1440x1720 is a good target resolution (About 2.5mp). I've been going a bit higher at 2500x3000 as my final output so I could print an 8x10 image without issue, but without any actual additional details of the image from the film.

I will update this with additional details as I fine-tune my process.

Samples:

Samples scaled too approx. 2000px across which is plenty for any details in the print.