Focusing on film grain

Hello there,

I have been scanning using my main mirrorless camera for some time now, and I have been noticing some inconsistency. I think this is mostly due to me not being able to properly focus on the film grain. Other variables such as level (using a mirror), film holder, light source, camera shake, etc are all being taken care properly I am pretty sure.

Thing is some scans are in sharp some others are not.

I have been trying to focus on the film grain, but when it comes to 100ASA film it’s fairly difficult.

The camera I am using, a Leica M10-R, I know it’s not the best when for this task, but I am not willing to buy another FF camera just for scanning. I am using a vivitar 55mm vintage macro lens (1:1) which is great in itself. I am using focus peaking and 6x zoom on the film, using a 2.8f when focusing: the problem is sometimes I really can’t see the grain and I have no idea where to focus otherwise. What I tend to do in this kind of situations, is to focus on the film branding, but my holder does not allow me to simply focus on that.

Do you have any recommendations?

What’s your iris set to? If it’s wide open, try stopping down to f8 or higher get a little more depth of field.

Hi there,

I tried both wide open and stopped down. Thing is if I stop down, I get the focus peaking to catch other parts of the negative, that are not necessarily the grain. And this is due to the depth of field being wider due to the small aperture.
I seem to remember that it was recommended to use a wide aperture for this reason. However after trying both approaches, I am still struggling.

Two things come to mind:

  1. Focus Shift: Focus shifts when aperture is changed. If this were the case, sharpness would not be good in a some shots and not in others, unless they were taken with different apertures…
  2. No Focus Peeking: Have you tried without using focus peeking? Simply focusing by looking where the image looks sharpest? Low iso colour films don’t have very pronounced film grain. Also, I noticed that focus peeking only shows things that are oriented in one way, say horizontally, on my EOS M6. I have to verify if FP will actually “signal” on grain only.

Update: I ran a few tests and found that autofocus (as opposed to manual focusing) works really well on my Canon EOS M6. Both AF and FP signals are taken from what the sensor sees, so why should there be a significant difference? I tested with a 645 negative. In combination with an APS-C sized sensor, reproduction ratio is nowhere near 1:1, where I found AF to struggle. I can get a tad closer when focusing manually for the reproduction of FF negatives with a FF camera.

Hi there,

thanks for getting back to me.

  1. This is something I have not considered, but I did a few tests yesterday, and none of my dslr scans were in focus. It’ s clearly a user problem. I was trying to dslr-scan some fuji velvia 100, and as I was having some issues focusing on the grain (if any) I attempted to focus on the edge of the frame, hoping this would work. It was not the case unfortunately. With regards of focus shift, I do not change the aperture between shots, therefore I would be surprised.

  2. I have not tried without focus peaking, this is something I can give it a go actually.

I had an idea, which could probably be completely useless…let me know.
What if, by using a sharpie, apply a little dot on the edge of the frame (outside the image) and then focus on that. Would that black dot from the sharpie be something I could focus on and achieve grain focus maybe?

Thanks for your continuous support.

Focusing on the edge might not be too helpful, unless

  • the negative is really really flat
  • the lens has no field curvature, which should be the case with a macro lens

I’d try the following if I had your gear (and in liveview)

  • focus with and without FP and see if sharpness changes between the two
    → keep aperture open to avoid focus shift issues
  • repeat and reduce aperture to between f/7 and f/11 while focusing.
    → see what f-stop works the best
  • don’t try to focus on (possibly microscopic) grain, but on image content
    → focus on eyes or hair, leaves, grass etc.
  • set focus and slightly change the distance if your gear allows it
    → focus bracketing is not fun, but it can give you an idea of how critical setup can be

All of the above will not help, if the original negative is not sharp :crazy_face:

Thanks I will give it a try.
One of the reasons why I was a little hesitant on focusing on the image content is that I may/may_not remember what in the image is really on focus and what not, especially with older negatives shot some time ago.

…no need to remember. Just have a look at the image with our without a loupe. The beauty of film photography is that it’s relatively low-tech. :grin:

BTW: Enlargers used to come in two flavours: Condenser and condenser-less.
Condensed light produces more acute reproductions, specially of B&W film. Condenser-less enlargers were used for colour mostly.

You should test your camera and lens combination and find the best focus aperture. Shoot a series of shots from your widest to smallest aperture keeping the ISO, shutter speed, and WB constant. Compare them one against the other in Lightroom or some other software and pick the sharpest aperture. For example, I’m using a Sigma 70mm macro lens on my Sony a7iii and the sharpest aperture was f/13. Remember, your camera and photo object are fixed so shutter speed is irrelevant. You just want a sharp image. Plus, that f-stop gives me extra depth of field so even if the autofocus, focus peaking, or eyeball focus is off a little bit, the image will probably be sharp as it is within the depth of field of the lens.

I hope this helps a little.

Agree. Wide open is rarely the sharpest aperture for any lens. A smaller aperture gives a wider depth of field which make focusing much easier.

Depth of field at micro distances is fantastically thin, and depth of field is the “almost sharp” part of the image that is “acceptable.” At 100% on a computer monitor, you can really see that it’s only really sharp where you focus. It takes a really good modern lens to be sharp wide open, have no field curvature and no focus shift (which changes the point of absolute focus as you stop down) i.e. further beyond or closer than the focused position wide open. My setup: Nikon D850, 60mm f/2.8 G Micro-Nikkor, manual focus. I always focus wide open at maximum magnification. With my previous lens, a 60mm f/2.8 Micro-Nikkor AF-D, I had to focus one third of the way in from the long edge for the stopped-down focus shift and flattening of field curvature to work, and it was hit or miss. I switched to the 60mm G lens and it is sharper wide open and stopped down, with flat field and higher performance at all apertures. Remember that any lens is diffraction limited past effective aperture f/8. Since marked apertures are defined at infinity focus, focusing so closely extends the lens focal length and your marked apertures are not your actual working apertures. At 1:1 distance a lens with no focal-length-shortening at 1:1 (Nikon and others do this kind of design) must be at marked position f/4 to be effectively f/8. Your lens might be at marked position f/4.5 or so to give you effectively f/8 at 1:1. So focus wide open or maybe one stop down.

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This strategy works for me:

  • Manual focus without focus peaking
  • Move the camera with lens to focus. I use a macro sliding stage.
  • Use a large screen TV as my viewfinder. Mine connected with HDMI.
  • My camera will “live view” magnify the viewfinder image for manual focus – and use it
  • Set aperture for sharpest image and use same for focusing
  • Use a remote trigger for camera exposure.
  • You may need to change your rig to reduce vibration. I found that vibration induced camera motion caused serious loss of sharpness

I found a 35mm lens testing target to be very helpful for diagnosing sharpness problems-- and evaluating my lenses. This is the one I use

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