Shading strip on LS-40

b4t · Jul 27, 2025

Hello all,

I scan 35mm films with my LS-40, and I get a "shading strip" on the left border on most of my pictures.

It more or less visible depending of the picture (it's exposure?). It happens with B&W and neg color films.
It's not on the film: the strip is not on the pictures I previously scanned with a LS-2000.

I use SA-21, with VueScan on Linux.

A dirty mirror? A light leakage?
Any idea is welcome!

brbo · Jul 27, 2025

Clean the mirror.

b4t · Jul 27, 2025

I will try that. I'm a little afraid of damaging the mirror. I wouldn't want to manipulate it if not needed.

I thought the main consequence of a dirty mirror is getting blurry pictures.

brbo · Jul 28, 2025

Well, you will get that kind of problem when the image area of the negative is not completely masked and the light shining through the unexposed part will bloom into the image area. This will be more pronounced when the mirror is dirty.

Maybe your mirror is perfectly clean and this is a problem with the holder that doesn't position the negative properly so the gate doesn't mask the unexposed area of the negative perfectly. If you have a piece of unexposed slide film, make a tiny hole in it and scan it. See how much flare you get around the hole. Compare your results to what some other people get (a few examples here...).

b4t · Jul 28, 2025

Thanks. I will try that as soon as I find time.

Other ideas:

Using FH-2 to see if film hidding unexposed border changes anything,
Switching the scanner off while scanning, to see the film position at this time.

About unmounting the mirror, I saw 2 methods on Youtube: upside up with some paper to receive the mirror when it falls, and upside down with some difficulties to grab it. Any advice?

Can I expect to see the mirror condition without unmounting it? Or is it too hidden to see anything?

brbo · Jul 28, 2025

I'd definitely try using a different holder, putting film the other end first, etc. to see if anything changes.

I don't know how accessible the mirror is in LS-40, but I'd try to find a way without full disassembly and get to the mirror with a bent cotton swab...

b4t · Aug 1, 2025

So, so...

1st step: cleaning the mirror

That's not that difficult. I put the scanner upside down, removed the clip, and and took gently the mirror off.

It was dirty. I used isopropyl alcohol and lens-cleaning Kodak sheets.

It's now cleaner, but, it cannot got it clean. It seems pitted (and has a scratch).

(Not easy to shoot a mirror! )

I tried some scan:

Inverting the film direction:

The problem is roughly the same on the other side.

2nd step: trying another film holder (FH-2)

Once the picture positioned in the holder, the picture border is completely masked by the holder plastic frames.

The picture has no strip.

My conclusion is the shading strip comes from using SA-21 with dirty/pitted mirror.

The SA-21 gate is larger than the exposed picture (feature to ease positioning with a simple cropping),
The dirty/pitted mirror spreads the light onto the picture border, which is visible especially when the border is bright (dark on film).

Seems I will try to buy some replacement for my mirror.

Archiloque · Aug 1, 2025

There are relatively cheap mirrors available on aliexpress. Unfortunately it's 5 units per order.

There.

Patrick Robert James · Aug 1, 2025

I'd clean the front of the lens as well when you install the new mirror.

There is a Coolscan group on Facebook if you are on there. Easy enough to ask if anyone has mirror you can get from them. There is one guy who repairs them too so he would have one for sure.

b4t · Aug 15, 2025

I've just changed the mirror (https://nbtg.dev/product/coolscan-mirror/, cheaper from Netherlands to France), but there is no change.

My main suspect is now the SA-21. It's seems to works correctly and I don't see any physical defect. I tried to add black gaffer on SA-21 border (upside, since the light comes from there), to prevent any possible light diffusion. No change.

Of course I could use FH-2, but it's much much slower for scanning rolls. Am I alone with this issue?

Other ideas?

b4t · 2025-09-14T04:50:00-0400

Other test: masking borders.

On the scanned picture, there is no more shading strip. But one can seen some blurred light strip.

So, no solution in this way. I don't see any hope to align frames and replacing shadow by light is not good either.

b4t · 2025-09-14T05:01:19-0400

Another test with a LS-8000 and the FH-835S film holder.

Of course, the result is good.

I tried to shift the film to have the picture border in the scanned frame.

I do not see any shadow on the left of the picture!

So having the empty space between the picture in the scanned frame does not necessarily lead to a shading strip.

I don't know if it's a defect of my LS-40 (dust somewhere?) or a design defect of all LS-40 (and maybe LS-4000, LS-50, LS-5000). I don't find any strip on my old pictures scanned with LS-2000.

Shading strip on LS-40

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