Camera scanning on the cheap -- an example approach

[rdeloe]

There’s a really long thread about “DSLR scanning” already on the forum, so think of these posts in this thread as a child of that conversation that might be useful for people who want to build a straightforward, cheap and reliable way of “scanning” 4x5 negatives with readily-available equipment. Needless to say there are endless other ways to do this – many of which have already been mentioned in the big “DSLR Scanning” thread. Think of this posting as some detailed notes on one specific approach. If what I’ve done meets your needs, the approach is relatively easy (and cheap!) to replicate.

My goal was to develop a system for easily producing “scans” of my 4x5 negatives at 2,667 ppi. I’m not interested in scanning at the highest possible resolution I might potentially need; if I ever need more than I can produce using this approach, I’ll have the negative drum scanned. Instead, I’ve designed a system to give me what I actually need most of the time. Note that the basic design is easy to adapt (e.g., if you need more ppi).

In addition to some notes on the “hardware” I’m using, I’ve also written up some comments for people, like me, who are working mostly in Lightroom (last post in this initial set).

If you find this useful, great. If you have suggestions for how to improve the design of the system -- also great and most welcome.

Rob de Loe
Guelph, ON

[rdeloe]

THE HARDWARE SIDE

My system is based around a Fuji X-T2, which has an APS-C sensor that produces 6000x4000 pixel RAW images in 3:2 aspect ratio. I use this camera to make 12 overlapping images, each of which covers 2.25” x 1.5” of a 4x5 negative.

Just about any modern high resolution digital camera can be used for camera scanning. However, if you want to duplicate what I’ve done here you need 6000x4000 pixels, or you need to start making adjustments to the setup. For example, if you use a Sony Nex 5 with a resolution of 4592 x 3056 pixels, you’ll get 2,041 ppi if you use 12 overlapping images that each cover 2.25” x 1.5”. If you want more final resolution in your “scan” of a 4x5 negative from that camera, you’ll need to shoot more frames. As another example, if I replaced my Fuji X-T2 with a Sony A7R III, I’d have a final resolution of 3,534 ppi (7,952 pixels on the long edge divided by 2.25”). You could shoot fewer frames to get 2,667 ppi, but you’ll have to redesign the scanning template.

Any good quality “macro” lens will do. It doesn’t have to be a proper macro lens that reaches 1:1 (unless you want more resolution). I’m using an Olympus OM 90mm f/2 macro lens, which just gets to my target image area of 2.25” on the long edge. I shoot in RAW, and use f/5.6 to get the best balance of depth of field and image quality from my OM 90/2 lens. I also have an Olympus OM 80mm f/4 lens with the 65-116 variable tube, but on my APS-C camera the largest image this lens/tube combination can record is around 2” (too small for my needs). If I ever need more than 2,666 ppi, the OM 80/4 will be superb. Importantly, using these film-era SLR macro lenses on an APS-C sensor allows me to use only the best part of the image circle. As good as the OM 90/2 and OM 80/4 are, they’re a bit softer at the edges than in the centre – so APS-C is a good choice.

A copy stand to hold the camera is ideal, but I don’t own one. Like many people, I do own some sturdy old tripods and heads that I don’t use anymore. I put an old aluminum Manfrotto tripod and 3-way head back into service for this job. Anything sturdy will do. I’m only scanning 4x5 negatives, so once it’s all set up in the right position, it doesn’t need to be adjusted again (unless it goes out of alignment) or I have to take it down and set it up again. If you want to get a bit fancier, use a macro focusing rail.

My light source is a cheap Chinese LED light pad ($25 on Amazon). I’m only scanning black and white negatives so my concern was consistent light, rather than colour temperature. As you can see in the pictures, the light pad slides underneath the scanning template. Even though it’s cheap, it provides excellent light for my needs. You can spend vastly more money on the light source if you want.

I tried various dry mount approaches, but I recommend fluid mounting. You’ll get fewer scratches and less dust with fluid mounting. It’s easy to do and holds the negative nice and flat, with the emulsion side down. In my setup, the negatives are fluid mounted onto an 8”x10” piece of glass. I’m using plain picture framing glass – nothing fancy like Anti Newton Ring (ANR) glass. It cost me a few dollars a piece. In the picture you can see four disks under the glass; these are “glider” feet, the purpose of which will become clear shortly. What you can’t see in the picture is that I scribed guide lines into the underside of the glass to mark where the negative needs to be. In my setup the negative needs to be precisely in the middle of the 8”x10” glass negative holder. These scribed lines don’t disappear when I clean the glass (unlike guide marks made with a marker).

The mounting fluid I use is Gamsol Odourless Mineral Spirits. (There’s a thread on the forum that discusses this product.) It works extremely well and is cheap in comparison to almost all the other options. Negative dry with no residue that I can see once I remove them from the mount. I’ve been using 0.005” acetate from the art store that I cut into pieces around 6”x8”. Once I finish my supply of that material I’ll be buying some “Grafix Clear .003 Dura-Lar Film” -- a better yet still inexpensive option that has also been the subject of a previous thread on the forum. The other fluid mounting tools I’m using are a semi-hard rubber “brayer” (the roller you can see in the picture), a blunt-tipped syringe for dispensing the fluid, a microfiber cloth for final polishing, and some wipes. You can easily find guidance on how to fluid mount on the Internet.

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[rdeloe]

The only somewhat complicated piece of the puzzle is the “scanning template”. You want to be able to keep the camera in a fixed position, and move the negative underneath it into the positions that provide the necessary coverage for reliable stitching. You also need to mask out extra light from your light source. My initial efforts involved simply moving a negative around under the camera, with some crude positioning using rulers. Results were hit-and-miss because I couldn’t keep everything lined up properly.

In the big “DSLR Scanning” thread you’ll see an amazing semi-automatic machine where the negative is moved around under computer control. I’d love to have that setup, but in the meantime I built myself a “scanning template”. The dimensions are in the sketch I posted. Needless to say I couldn’t achieve the precision in the measurements shown in my sketch… That’s OK though because consistency is more important than perfectly equal amounts of overlap between frames.

Anyone with some basic tools and skills can make one of these scanning templates. (Trust me – I’m no carpenter!) I built it out of bits and pieces of materials I had lying around already (scraps of wood, bits of moulding). The base of the template is a piece of particle board shelving. Some bits of left over moulding provide the outer “walls” that enclose the working area of the template, within which the glass is moved around. The grooves in the surface (which hold the rulers you can see in the pictures) are 5/8th inch deep cuts and made with a circular saw. The plastic rulers that serve as guides (see below) cost a bit over a dollar a piece and are exactly the right width to slide easily into the grooves yet still provide a secure “edge” for positioning shots in the middle of the frame. A better carpenter than me could have made a non-embarrassing window to expose the LED light source that sits under the template. Mine looks like it was chewed open by rats, but it works. It’s just a bit bigger than the 2.25”x1.5” target image size. I used some left-over matte black spray paint from another project to finish it off.

When you are camera scanning, the lens plane, sensor plane and the plane of the negative should be absolutely parallel (or as close as you can get). To ensure the scanning template is level, I installed four “furniture levellers” that allow each corner to be raised and lowered independently; these cost a few dollars at the local hardware store. I level the camera using the old trick darkroom workers know well for levelling their enlarger: place a mirror underneath the camera, on top of the level scanning template, focus on the front of the lens, and then adjust the camera until the front of the lens is dead centre in the frame. I find this is much more accurate than putting a level on the camera.

To get 2,666 ppi on a 4x5 negative with a sensor that collects 6000x4000 pixels, you need to shoot four rows of pictures in landscape orientation that each cover 2.25”x1.5” of the target 4x5 negative, with each row having three overlapping pictures. You can shoot fewer pictures. However, having plenty of overlap increases the odds of successfully stitching the set together. In my design, I’ve allowed for around 40% overlap between rows, and 33% overlap between columns.

To use this outfit to make your 12 pictures, you position the 8”x10” glass negative holder (with the negative fluid mounted in the centre) in the scanning template, and then move it around under the camera to get each shot. I start in the bottom-right corner and take the first picture. I then insert the short ruler into the vertical cut, slide the negative holder along the bottom edge of the template until it stops at the ruler, take the second picture, remove the ruler, slide the negative holder into the bottom-left corner of the template, and take the third picture. That’s the first row. I repeat this for the next three rows, except I use the long ruler to position the negative holder for the middle two rows. The top edge of the scanning template is used to make the final row. The glue-on gliders attached to the bottom of the glass negative holder allow me to slide the negative holder without scratching the glass. I can shoot all 12 pictures in a couple minutes at most.

I always use a cable release or self-timer to eliminate camera shake. You’ll need to experiment to see how to expose the shots. I’ve had good success by over exposing by about 1/3rd of a stop. The result is a relatively “flat” scan.

[rdeloe]

THE RESULTS

Here’s an example from a negative I made in 1992 along the shores of Georgian Bay on Lake Huron. The film was FP4+. I can’t remember for sure but I think I was using D76 at that time. The lens was a Schneider APO-Symmar 150mm f/5.6. This negative was a bit on the thin side compared to other ones I made at the same time; I thought it scanned better than the denser version.

When I tried printing it in my darkroom, I wasn’t able to make a print from this negative that made me happy. I’m glad I gave it a second chance in this new workflow. The picture I’ve attached to this post is a quick work-up from a camera scanned version of the picture. Scanning (including fluid mounting), processing in Lightroom, and spot cleaning in Photoshop took about 15 minutes total. That time will go down as I get more proficient. With a few adjustments in Lightroom, I’ve been able to get to a decent work print quickly.

I’ve included a 1:1 portion of this picture so you can see the amount of detail I was able to pull from the negative. This is from the processed version, so it’s been sharpened appropriately. There’s plenty of information in this file for prints much larger than I can make on my Epson 3880. A print that is 34” in the long edge would still be in the ideal 360 ppi territory for Epson printers. If I ever need to print larger, I’ll have the negative drum scanned.

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[Peter De Smidt]

Good system, and a terrific write-up!

[Daniel Stone]

Very nicely done! I agree with Peter, very well documented! I have been considering this as a viable alternative, seeing that flatbed scanning is a pain when you want to scan flat(and having owned a drum scanner in the past, I appreciate wet mounting as much as possible.

-Dan

[rdeloe]

Thanks for the feedback Peter and Dan. If you have any suggestions for improving the design or work flow, please feel free to post them. I consider this a prototype and am always open to better designs and approaches.

[Tin Can]

Very good and you are an excellent writer.

I won't be doing this, but at least i know how you do it.

Thank you!

[Peter De Smidt]

Well, the obvious upgrade is an automated positioning system. They really aren't that hard to build, and the software and parts lists are freely available, though I don't know offhand if the triggering mechanism will work for Fuji. Daniel and my systems were both Nikon, but that can't be that big of a problem.

[rdeloe]

Indeed! My kid just started Engineering. I told her she had one year to learn what she needed to learn to build me one! ;)

I'm pretty sure the triggering mechanism won't work on Fuji. When I'm working digital, I sometimes use Helicon Focus to do focus stacking. The software offers the ability to let the camera determine the number of frames needed in the stack to get everything you want in focus. Unfortunately, the developer told me it only works on Nikon and Canon cameras -- and specifically not Fuji X series bodies. A good used Nikon or Canon body that would work well for this purpose wouldn't be too expensive, so that's an easy enough problem to solve if I go that route.



Well, the obvious upgrade is an automated positioning system. They really aren't that hard to build, and the software and parts lists are freely available, though I don't know offhand if the triggering mechanism will work for Fuji. Daniel and my systems were both Nikon, but that can't be that big of a problem.

[Peter De Smidt]

Doesn't the Fuji have some type of cable release?

If she wants to use an Arduino, then this might be of some help: https://github.com/nSomnius/Scanduino-by-ReallySmall

[rdeloe]

She just learned Arduino so that link is perfect. Thanks.

Is it as simple as a cable release? It actually has an old-school screw-in release, but you can also use an electronic release. I assumed it was a more complicated control setup, but if it's just triggering the shutter via the plug that should work.


Doesn't the Fuji have some type of cable release?

If she wants to use an Arduino, then this might be of some help: https://github.com/nSomnius/Scanduino-by-ReallySmall

[Peter De Smidt]

Sure. We use what's basically an electronic cable release. All the camera needs is a momentarily closed circuit. First pulse and the mirror goes up. Second pulse and the shutter fires. I'm not sure why the various software, such as Helicon Focus, won't work with fuji. There are fancier connections that control aperture, shutter speed....but those aren't needed for a scanner.

Maybe I should just send you some scanner parts....although not the Velmex Unislide.

[rdeloe]

That's a very kind offer Peter. However, if I go down the route of building a system like the one you devised it won't be for a while. The reason is I'm already bumping up against one annoying problem inherent to any "stitching" approach: it's not uncommon to have negatives where stitching fails because the software can't figure out how to put two images together due to lack of detailed elements that can be matched up. This is where scanners win the day (no stitching).

In some of your previous posts in other threads you mentioned you used templates in PTGui to line things up. I presume that only works when you can be assured that each frame is exactly in the same position each time. That's more likely with your computer controlled setup than with a manual setup like mine. To cut to the chase, when your system was up and running, would you have been able to stitch a 4x5 negative that was mostly low detail? An example is a landscape shot where there's a tiny band of "land" at the bottom and a lot of sky with no clouds in most of the frame. Or most of the pictures from Thomas Joshua Cooper's Atlantic Basin Project where there's a lot of soft ocean and sky. My current setup would fail on probably half of Cooper's pictures.

I wouldn't want to make the effort to build a more sophisticated camera scanning setup that still failed me on the stitching end!

Rob





Maybe I should just send you some scanner parts....although not the Velmex Unislide.

[Tin Can]

Another question is, how many and what size stitch captures can be done with available software such as Photoshop CC?

I tried stitching many, I forget the number, maybe 50 images of a wall mural some years ago. PS CC failed at some point. I had to do sections. Then stitch those. Not ideal.

Just anticipating larger film sizes, like 8X10 and up.

I think specialized stitching software does better than PS CC. IDK

[Peter De Smidt]

"To cut to the chase, when your system was up and running, would you have been able to stitch a 4x5 negative that was mostly low detail? "

Yes. :) You wouldn't really be building a system. It'd be more like re-connecting. To be more accurate, I built my system on a plywood table. I stapled control cables to the table to keep them out of the way. When I took the system down, I cut the cables. I'd be happy to send you everything but the Velmex unislide. So you'd have to come up with a way to attach your camera to the structure. Even if you don't want to mess with connecting the camera to the Arduino, you could let the Arduino control negative stage movement, and you could simply use a cable release to lock the mirror and fire the camera. You'd have to probably change the overlaps, as I used a full frame camera, but that shouldn't be too big of a deal.

For Randy, I don't suggest scanning 8x10 at 1x. How big would you print? I'd work backwards from that, giving yourself a little wiggle room. For example, with a 24 megapixel camera, wouldn't 6 sections suffice with 8x10, even with the overlap?

[Tin Can]

Rob, Peter, I am not going to make a DSLR scanner, but do admire your efforts.
However we do spend a lot time here discussing scanning.
Which is fine with me.

I wonder if new LF/ULF scanners may come to market.

Before I upgrade to a V850...

[nomennominatur]

Although, by comparison, my own setup is quite rudimentary (see image below), I venture to add my 2 cents:

1) By substituting my standard glass with two strips of high quality museum glass cut to my needs (inexpensively sourced from a gallery/framing shop), results improved substantially, obviating the need for wet mounting, thus speeding up my workflow.

2) Using the DSLR tethered to my mac, employing a dedicated tethering software ("Sofortbild" freeware) I can focus on grain in live view 1:1 on the notebook without any eye strain. This, with my Nikon, works much better than LR tethering. The software allows for deferred exposure so that any tripod vibrations from hitting the mousepad will have settled. Of course, I use mirror pre-release on the camera.

3) I humbly move the negative setup manually. This is not much of a problem for me, because I prefer generous overlap anyway, to ensure hassle free automatic stitching results in PS.

4) Cheepskate me, I even skipped the 25$ LED lighttable, because for b&w my iPad (arguably more than 25$) will do nicely with a 3" deep spacer (black wood frame) to obscure display pixels.

5) I prefer to stop down a bit more with my 105 mm Micro-Nikkor (f/16-f/22), since it is not a dedicated copying lens and does have some residual field curvature. This also takes care of minor levelling adjustment errors.

Originally, this setup, employing my 10 year old D700, was an interim solution for 35 mm, when my dedicated negative scanner was away for service. However, in the end, I preferred the results due to less "pseudograin" interference of scanner resolution with film grain on some of the more grainy films like HP5. I meanwhile use it for MF and LF, too.

Kind regards
Mathias


Setup:

186696

Example:

[ I apologize that, due to storage limitations of my personal website, the link to a haphazard medium format scan will have to do. Even in the compressed jpg, zooming in on the sweatshirt fabric shows a satisfactory result imho, but other's eyes may be more discerning ]

47 megapixel jpeg of example:
http://galerie-elsner.de/pictures/Vb

Thumnail of example:
186698

(Rolleicord Vb with Schneider Xenar 75 mm f/3.5)

[rdeloe]

Thanks Mathias.

From the picture it looks like you're using the "glass sandwich" approach. Is that right? You've sandwiched the negative between two pieces of glass? This "museum glass", is it the anti-reflection kind? If so, how are you positioning them -- e.g., is the roughened side of the glass facing inwards?

The tethering approach looks very interesting. Unfortunately Sofortbild only works with Nikon. I have to get serious about finding something that works well with Fuji. Mind you, focusing with live view on the Fuji is actually very easy.


Although, by comparison, my own setup is quite rudimentary (see image below), I venture to add my 2 cents:

1) By substituting my standard glass with two strips of high quality museum glass cut to my needs (inexpensively sourced from a gallery/framing shop), results improved substantially, obviating the need for wet mounting, thus speeding up my workflow.

2) Using the DSLR tethered to my mac, employing a dedicated tethering software ("Sofortbild" freeware) I can focus on grain in live view 1:1 on the notebook without any eye strain. This, with my Nikon, works much better than LR tethering. The software allows for deferred exposure so that any tripod vibrations from hitting the mousepad will have settled. Of course, I use mirror pre-release on the camera.

3) I humbly move the negative setup manually. This is not much of a problem for me, because I prefer generous overlap anyway, to ensure hassle free automatic stitching results in PS.

4) Cheepskate me, I even skipped the 25$ LED lighttable, because for b&w my iPad (arguably more than 25$) will do nicely with a 3" deep spacer (black wood frame) to obscure display pixels.

5) I prefer to stop down a bit more with my 105 mm Micro-Nikkor (f/16-f/22), since it is not a dedicated copying lens and does have some residual field curvature. This also takes care of minor levelling adjustment errors.

Originally, this setup, employing my 10 year old D700, was an interim solution for 35 mm, when my dedicated negative scanner was away for service. However, in the end, I preferred the results due to less "pseudograin" interference of scanner resolution with film grain on some of the more grainy films like HP5. I meanwhile use it for MF and LF, too.

Kind regards
Mathias


Setup:

186696

Example:

[ I apologize that, due to storage limitations of my personal website, the link to a haphazard medium format scan will have to do. Even in the compressed jpg, zooming in on the sweatshirt fabric shows a satisfactory result imho, but other's eyes may be more discerning ]

47 megapixel jpeg of example
http://galerie-elsner.de/pictures/Vb

Thumnail of example:
186698

(Rolleicord Vb with Schneider Xenar 75 mm f/3.5)

[nomennominatur]

Thanks Mathias.

From the picture it looks like you're using the "glass sandwich" approach. Is that right? You've sandwiched the negative between two pieces of glass? This "museum glass", is it the anti-reflection kind? If so, how are you positioning them -- e.g., is the roughened side of the glass facing inwards?

The tethering approach looks very interesting. Unfortunately Sofortbild only works with Nikon. I have to get serious about finding something that works well with Fuji. Mind you, focusing with live view on the Fuji is actually very easy.

I am aware that anti Newton glass should display some roughness, however, neither with naked eye, nor with a 10x loupe am I able to discern any roughening. However, I do not get any Newton rings at all, sandwiching the film without any spacers. I am a bit puzzled myself. The glass is from a rather prestigeous framing shop out of town. Next time I go there, I will ask the owner about the technical details of this archival glass, which he uses only for the most expensive framing jobs. The glass is rather thin, thus the top glass does not brutally weigh down the negative, yet flatness is more than sufficient for my DOF setting.

Kind regards
Mathias

[Larry Gebhardt]

I am aware that anti Newton glass should display some roughness, however, neither with naked eye, nor with a 10x loupe am I able to discern any roughening. However, I do not get any Newton rings at all, sandwiching the film without any spacers. I am a bit puzzled myself. The glass is from a rather prestigeous framing shop out of town. Next time I go there, I will ask the owner about the technical details of this archival glass, which he uses only for the most expensive framing jobs. The glass is rather thin, thus the top glass does not brutally weigh down the negative, yet flatness is more than sufficient for my DOF setting.

Kind regards
Mathias

Perhaps your museum glass is the type with an antireflective coating on it? If so make sure you clean it like you would a camera lens. I have a few sheets I've tried in the enlarger and they seem to do a decent job with newton rings on most of the time.

[nomennominatur]

Perhaps your museum glass is the type with an antireflective coating on it? If so make sure you clean it like you would a camera lens. I have a few sheets I've tried in the enlarger and they seem to do a decent job with newton rings on most of the time.

Thanks. Multicoating seems to be an option, indeed. I just came across this:
https://tru-vue.com/solution/museum-glass/

But then, coating should not affect presence or absence of Newton rings which are a function of wave length and spacing, if my dim recollection of college physics does not fail me...

[Larry Gebhardt]

Thanks. Multicoating seems to be an option, indeed. I just came across this:
https://tru-vue.com/solution/museum-glass/

But then, coating should not affect presence or absence of Newton rings which are a function of wave length and spacing, if my dim recollection of college physics does not fail me...

By reducing the reflection you reduce the rings since they are interference patterns created from the reflection of light between the two surfaces.

[Peter De Smidt]

Yes, my experience is that multi-coated glass does reduce Newton's rings, reduce but not eliminate.

[nomennominatur]

Larry and Peter, thanks, that makes sense.

[Jeroen]

...The tethering approach looks very interesting. Unfortunately Sofortbild only works with Nikon. I have to get serious about finding something that works well with Fuji. Mind you, focusing with live view on the Fuji is actually very easy.

Capture One Pro (v.11 or now v.12) is your best option for tethering Fuji camera's. Really fast, and it's also the best raw converter, most pro's swear by C1. Has a bit of a learning curve though and it's not cheap (though there is a cheaper Fuji-only version). Download a free trial at https://www.captureone.com

[Peter De Smidt]

I agree with Jeroen about Capture One and Tethering. It's the best solution I've used.

[Blackmarxz]

When you are camera scanning, the lens plane, sensor plane and the plane of the negative should be absolutely parallel (or as close as you can get). To ensure the scanning template is level, I installed four “furniture levellers” that allow each corner to be raised and lowered independently; these cost a few dollars at the local hardware store. I level the camera using the old trick darkroom workers know well for levelling their enlarger: place a mirror underneath the camera, on top of the level scanning template, focus on the front of the lens, and then adjust the camera until the front of the lens is dead centre in the frame. I find this is much more accurate than putting a level on the camera.



Ahhhh Furniture levellers...... Thanks very much - I was thinking of ways to properly align my camera

[MartinP]

Ahhhh Furniture levellers...... Thanks very much - I was thinking of ways to properly align my camera

One could also use three, then it would always be stable during adjustments. Or use a baseboard with three wooden wedges underneath at the edges, moving them in and out to level the baseboard and securing them temporarily with a bit of tape.

[Roberto Nania]

Hello to all.
I need an advise on a freeware software that has a color negative to positive feature.

I use MS Paint.net for viewing my scans since I don't need any high resolution or super adjustment for printing output.
Unfortunately, I cannot covert color negatives into positive with it (only "invert colors" which turns a color negative into a total blue image).

Thank you!

[grat]

I've been touting Darktable as an option recently, since they added their 'negadoctor' plugin.

So first, https://www.darktable.org/ is an open source package that started as an alternative to Lightroom. It's really designed for RAW development, batch processing, organization, culling, proofing, etc.. It's more Lightroom than Photoshop. It's also "non-destructive"-- all of your edits, adjustments, crops, rotates, etc., are stored in metadata files, rather than changing your source image. This also makes it easy to apply those edits to other photos.

It's available for Windows, Mac OS and Linux-- while it's part of most linux distributions, be aware you need at least version 3.1 (3.2 is better) for the negadoctor plugin, and many distributions lag behind the latest and greatest by a few months.

negadoctor seeks to fill the same role as Negative Lab Pro-- invert and correct for color cast. Automatic works pretty well, but you can also tweak in semi-automatic or full manual mode.

This video (and following videos) does a nice job introducing Darktable:

https://www.youtube.com/watch?v=899uLpO2W9w

And this one covers negadoctor:

https://www.youtube.com/watch?v=D8dlM_bCtig