This section provide brief overview of film holders for film digitizing. Find below brief descriptions of the holders from the different manufacturers and Vlads notes - prepend "IMHO" to each paragraph. 

This page is under review and will be updated soon with more info. 

What this page lacks so far is mentioning of use of classic darkroom enlarger's film holders /carriers for the purpose of camera scanning - will add that info later.

Intro

Film holders are as important for camera scanning success as a good lens and a proper high-quality light. Holder should perform number of functions:

• Hold film flat.

• Hold film reliably - meaning replacing the film strip in the holder should not break alignment and focus. 

• Holder should allow fine-tuning of film and sensor alignment.

• Holder should not obstruct or shadow the backing light.

• Holder should not introduce any artifacts and parasitic light reflections on its own.

• Holder should be stable - so advancing film should not move holder in any way.

• Holder should protect film from a stray light.

• Holder should not damage film even if film has dust particle on its own.

• Optionally holder may have means to advance film.

• Optionally holder may allow few film formats share the same base.

Tool to assess flatness of film is also in the works

I am also building the tool to objectively assess the flatness of a film in any holder. If I come up with the convincing results, I will publish them here. 

IMHO, these are the best value for money holders. They are not super cheap, but they do keep film flat in most circumstances and they are easy to use. The holders come in wide variety of formats from 110 to 135 to 120 to 4x5. The advancer and place for light source make those holders one of the very best. 

Web site: https://kamerastore.com/en-us/pages/360-system .VALOI 360 is available in USA at number of stores. See sample usage scenario here https://www.film4ever.info/gallery#h.i8f1ifnq8yss

VALOI recently started manufacturing very compact "easy 35" holders which resemble Nikon ES-2 adapters with light built-in. The device is the solid performer though its not as cheap (EUR 220+shipping) as many would like it. 

Negative Supply makes the whole range of holders and copy stands for any budget - from expensive to very expensive ;-) . I don't particularly like their Basic line of 35 mm holders as they do not keep film flat as good as VALOI. After all, the inserts where film actually flow is 3D printed so the surface is not as friction free as one would want. The more expensive models look very good, but I did not have chance to deal with any of them. 

Web site: https://www.negative.supply/

Pixl-latr is one of the simplest and compact solutions available on the market. Still it allows to scan basically any film format from 35 mm to 4x5 ". Of course it's up to user how to make the holder to sit still and have camera pointed properly at the right angle. This is very popular holder and one of the cheapest ones.

Web site: https://www.pixl-latr.com/  Pixl-latr is available in USA at number of stores.

Well done quality film holder from Korea with the film advance mechanism and a light. Perfectly usable in the most scenarios. Suitable for 35mm and type 120 films. Light quality color-wise  is unknown (to me).

Web Site: https://shop.lomography.com/us/digitaliza-plus-scanning-kit

As far as I know this is very decent holder, but I never hold it in my hands. It usually comes with Sunray Copy Box which is respectable name in camera scanning world. 

Available at https://cinestillfilm.com/products/sunray-copy-box-iii-film-holders 

Essential Film Holder is one of the oldest designs and has been sold in thousands of copies. The jury is still out whether it provides quality good enough for advanced user. The frequent complain is parasitic reflections from the holder's vertical borders which make funny things at the edges of scans. Those effects are much more pronounced when scanning negatives. I would very much want to see the slanted border around the film gate to eliminate the unwanted light reflections.

Web Site: https://clifforth.co.uk/

Nikon, Canon, Minolta all have produced slide duplicators from the times immorial and many of these devices are still perfectly good for camera scanning  today- especially if used with the native bellows. 

Nikon traditionally paid a lot of attention to slide duplicating and have issued number of devices. 

Nikon ES-1 (https://www.film4ever.info/gallery#h.2lu5gp7fgo8r ) is one of simpliest ones and can do only slides.

Nikon ES-2 is versatile device good for slides and strips of film . JCC adapter ( https://www.film4ever.info/gallery#h.7xzwe3glpyvo ) is basically the knock-off of Nikon ES-2.

Nikon PB4 and PB6 are very solid and robust devices. If used with Nikon bellows they are rock-solid, if one decides to incorporate them in its own design - certain metal working skills are required.  It makes sense to discuss these holders separately as they still unvaluable piece of equipment. 

There is number of designs of 3D-printed holders. Some of them are free to download and print, some are sold already printed. Again, you have to know what you are doing to use them successfully. Very often those holders have path height too high, so film is not flat enough, sometimes material is not as good and smooth as molded plastic so it takes certain effort to advance film. Some of them lack any mounting points so they are hard to fix in one place with required precision.

Film holders from classic darkroom enlargers would be the first thing one can think of when starting building a scanning rig. But beyond very well executed film path, there is relatively little those holders can offer. First of all they need to be mounted on some sort of stable base with the backing light underneath. That means drilling holes and attaching supports which have to be sturdy enough to carry the weight of a holder. Secondly, most holders have upper parts of assembly on the spring board to ease film advance. In film scanning scenario that may be too much of disturbance to keep the film frame in the focus. The depth of field is mere 0.3 mm in 1:1 scale at F/8 and focal length 70 mm. So making reliable setup with enlarger film holder is much more involved task than it seems. 

From website: "The Cassette Film multi-format film holder replaces time-consuming flatbed and expensive drum scanning. With the Cassette Film multi-format film holder for dlsr scanning, photographers can now easily scan films of varying sizes up to 8x10 sheet film without the use of time-consuming and costly scanning methods. The snap-in holders offer a convenient solution that not only speeds up the process, but also improves the overall workflow of photographers, allowing you to complete more projects in less time. The film holder's compact design allows for easy storage and transportation, making it a perfect option for photographers on the go. Plus, with the ability to scan a variety of film sizes, it's a versatile tool for any photographer looking to digitize and scan their film archives using Cassette film holders."

From Etsy website: "What is The Lobster Holder?

A film holder for DSLR scanning that holds the film perfectly flat AND allows for smooth and fast scanning. Feel the strength of a lobster claw! You get the holder for 120 films, that has been hand-made (i.e. I started the 3D printer), assembled and tested.

Properties: 

Good for every 120 format up to 6x9. Super fast operation, you can scan a roll under one minute. Holds film perfectly flat during scanning. Clamps down the film by the power of the Sun two neodymium magnets. Does not scratch the film as it returns to its natural curl when you release is, so only the edges actually touch the holder.  3D printed with high-quality PLA. The holder comes assembled and tested. The only thing you will need to do is to screw in the legs. And take it out of the packaging. Not necessarily in this order.."

4x5 : https://www.etsy.com/listing/1652789541/the-lobster-holder-4by5-4x5-large-format?ref=desktop_listing_share_button