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Third episode of my odyssey to digitize our entire family slides collection. If you want to know all the details of the project, I invite you to check my two other posts but here is a quick recap of the situation.

I modified a slide projector to be able to digitize fast a big number of slides by taking photos of them with a Nikon D5000 using a Macro reverse ring. I'm shooting both in RAW (NEF) and JPEG and both of these formats have visible noise.

I'm now near perfect image quality (at least to my appreciation) but there's one detail I'd like to fix: there's still too much noise on the photos in my point of view especially visible with blue sky or skin for exemple.

My camera's settings are as follow:

Aperture: manually set a couple of steps down from wide open (as advised in an answer of another question of mine)

Shutter speed: 1/400

ISO: 200

Exposure compensation: 0

Picture style: Neutral

White balance: custom (preset with no slide in front of the light)

I chose an ISO of 200 because that's the base ISO of the Nikon D5000. However I also tried with a 100 ISO and 1/200 Shutter speed but that gave no change whatsoever (at least not that I can see with my own eyes).

I don't know with which camera the slides have originally been shot so I'm not sure if I'm just shooting the noise that is already in the original shots or if the appearing noise has been added when shooting the slides with my camera.

Also, as advised in this answer I added several layers of tracing paper to best diffuse the light rays in all directions. The paper I bought is the best quality I could find with the least grain. So I'm wondering if the noise might come from this paper.

Photo sample with visible noise

So here are my questions:

  • Do you think the noise is already in the original shots?
  • If not, do you think that could be improved?

If that could be improved do you think that could be solved with any of these changes:

  • Changing the LED used for projecting the slides (I bought a cheap cool white 50W LED on Ebay)
  • Changing the shooting settings (Aperture, shutter speed, ISO, exposure compensation)
  • Changing the camera to use one with a bigger sensor size (full frame or medium format)
  • Removing some tracing paper layers or change it completely to another kind of diffuser
  • Another idea ?

Some changes are acceptable to me like changing the settings or the diffuser type and some aren't like buying a full frame camera for exemple. But even if some of these changes aren't doable I still would like to know if you think they might solve this issue.

I really would like to get the best photo quality before digitizing thousands of them.

Thanks for your answers.

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    \$\begingroup\$ It's certainly possible that the original slides have noise/ grain - One question: were these photos originally shot on slide film? or were they shot on normal negative file and slide copies made? This would be the first step that would introduce a degradation in quality. Do you still have a projector? can you project an image onto a completely white surface and look for noise/grain in that? then you'll know where they source is. Extra note: in your attached example, your focus seems a little off. \$\endgroup\$
    – Digital Lightcraft
    Nov 13, 2020 at 14:37
  • \$\begingroup\$ I'm pretty sure these photos were originally shot on slide films because we don't have any of these photos on paper format and I didn't find any negative films at my parents home. Yes my parents still have a working projector, I guess during Christmas I'll try to check some slides. But I must be quick because the original light bulb is producing lots of heat and makes the slide films pop. \$\endgroup\$
    – Jérôme MEVEL
    Nov 13, 2020 at 14:49
  • \$\begingroup\$ @DigitalLightcraft you're probably right for the focus, the thing is with the reverse ring I'm not able to focus properly. This is all very blurry and it's only once I take the shot that I can see a clear picture... I guess I should improve my focusing process and maybe write another SO question if necessary \$\endgroup\$
    – Jérôme MEVEL
    Nov 13, 2020 at 14:51
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    \$\begingroup\$ You can use a 50mm prime as a loupe. Look through the front of the lens. \$\endgroup\$
    – xiota
    Nov 14, 2020 at 21:19
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    \$\begingroup\$ @JérômeMEVEL What you keep describing as noise looks mostly to be film grain (which also means the slide is in pretty good focus and any blurriness in the photo is also blurry in the slide). Using the lowest level of in-camera noise reduction may give you a result you find more pleasing with the in-camera JPEGs (though the raw files will not be affected - unless your raw converter automatically applies NR based on the in camera NR settings recorded in the EXIF info), though it will slightly soften details in the JPEGs to which the NR is applied. \$\endgroup\$
    – Michael C
    Nov 15, 2020 at 23:31

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Perhaps not a total fix, but some ideas in hopefully a helpful direction.

I doubt the noise is camera noise at 100 or 200 ISO, if you are completely filling the frame of the D5000. My D5500 is newer, but I'm almost sure it couldn't be that much noisier than mine.
It is, btw, just about fixable in Photoshop, pic at the end of a quick 'fix' attempt.

To fix your focussing issue, shift the camera to Live View, then use the + [magnifier] button bottom right to zoom in as far as you can. Adjust manual focus whilst you can see one of the hardest-edged details in your slide.
[I've subsequently seen the new question & don't know why the reversing ring can't focus… unless it has no electrical connections]

You have some vignetting [a darker ring round the edges] - possibly because your diffuser isn't absolutely 'perfect' or your light source is too close behind it, or indeed that the lens itself [not designed to work that way round] is vignetting. You may not be able to fix this entirely, but you could perhaps swap out the tissue I previously suggested for some proper diffuser gel. You can get this for just a few $£€ on eBay. It is, comparatively, optically perfect. It may still not be quite enough to get rid of all the vignetting. This can anyway be fixed in Photoshop to an extent.

You also have a purple-ish colour shift. this might be the film or it might be your white balance, or even the LED. Probably film. It may well change between film batches too.

With some Photoshop 'magic' you could actually work out how to automate all of this - but that's definitely for another question [& someone better at Ps batch scripting than me].

Anyway - a quick attempt to smooth the noise, pull back some of the purple, punch up the remainder, knock back some of the over-bright centre & balance out the vignette. [It's not perfect, it's a 5 minute quick fix.]

enter image description here

eBay UK link to an example gel diffuser (not a recommendation, per se)

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  • \$\begingroup\$ Thanks again for your answer. The custom white balance has been done with the LED only so I guess the purple-ish color is coming from the original shot. I know the corner are darker, this is because the LED is a bit smaller than the slides. I added some aluminium paper to reflect the light rays even in the edges. This did reduced a bit the middle-lighter effect but not completely. This is only visible in landscape photos like this one. I guess I'd have to live with it \$\endgroup\$
    – Jérôme MEVEL
    Nov 13, 2020 at 17:39
  • \$\begingroup\$ I will try your advise about the diffuser gel, I think it will be better than my tracing paper. As for the zoom, I zoomed as much as I can so it fits both portrait and landscape photos. I automated everything from taking photos to automatic cropping. I'll give a try to the extension tube instead of reverse ring as you suggested. I really hope this will fix my focus issue \$\endgroup\$
    – Jérôme MEVEL
    Nov 13, 2020 at 17:42
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    \$\begingroup\$ Jérôme - I had another tweak at the picture, the purple was still bothering me, & solidified the centre of the image a bit more [OCD said 'try harder', that's my excuse ;) The vignetting is slightly off-centre, so that's quite hard to fix [I've probably over-cooked it now]. Wish you luck on the ext tubes. \$\endgroup\$
    – Tetsujin
    Nov 14, 2020 at 17:27

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