Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Our DIY Scanner

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.
Ann

Re: Our DIY Scanner

Post by Ann » 06 Jan 2010, 18:28

Thanks - Yes, the LiveView function has a live histogram - I was just admitting that I had no idea how to interpret it. Next time I take some photos I'll pay attention to the histogram and play with it. Thanks again.

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Re: Our DIY Scanner

Post by daniel_reetz » 06 Jan 2010, 20:12

Ann, your file is now hosted here:

http://diybookscanner.org/images/AMagCover.CR2

Misty's post was spot on. If you want any more info on histograms and reading them, I can also be of assistance.

I loaded your magazine cover into Photoshop. I have some technical advice if you want it. This post will be about the white balance of the image you posted. Forgive me, I'm sure you already know most of this.

To begin, I want to note that because you are shooting RAW, the white balance setting shouldn't matter all that much for the purposes of SHOOTING the work (there exists a technical situation, where it might affect per-channel amplifier gain, but I don't think that's the case with the XSI). The reason it won't matter much is because in principle, when shooting RAW, the "white balance" is decided AFTER shooting, when the RAW file is converted into an actual image like TIF or JPG. The camera setting is, in effect, only a "recommendation" and has little to do with your CR2 file. If you get it wrong while shooting, no big deal. Set it later.

However a CR2 file is of little use by itself. You need to convert it to a JPG or TIFF or whatever your grant specs ask for. That's because a RAW file actually doesn't contain color information like you're used to seeing in digital images. The color of each pixel in your final JPG or TIFF is inferred from the RAW file by some mathy business. One part of this mathy mess is the part that determines the "white balance" of the final image. As I mentioned above, your camera can try to measure the white balance of the "scene" (page in our case) which is called Auto White Balance, or you can manually set the white balance, as you have done. Both of these approaches only result in a "recommendation" that your RAW conversion software will use to try to make the right colors. But you can also set this white balance yourself, in your case in Graphic Converter, or in my case in Photoshop.

The problem that white balancing tries to solve is to correct for the "color temperature" of the light. Your camera is currently set to "Fluorescent", which is actually "3950K". So for example if your lights were very blue, they would make your image too blue. So you would want to "warm up" the resulting pixels to correct for the lighting. Or if your lights were too red, you would want to "cool down" the resulting pixels. That's the part of the equation that the white balance number slots into, that's the job it does.

OK, so what's your correct white balance? Well, I measured the white pixels in your image and calculated a correction. Although "fluorescent" was a reasonable choice, it seems that the actual color temperature of your lights is 6300k. My recommendation is to do a custom WB on your camera (check your manual, it's usually not too bad), or alternately simply to keep shooting as you are, but setting your RAW converter to the correct 6300K value. Here is your image before and after the white balance correction.
AMagCover_WHITEBAL.jpg
AMagCover_WHITEBAL.jpg (198.55 KiB) Viewed 4897 times

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Re: Our DIY Scanner

Post by daniel_reetz » 06 Jan 2010, 20:32

OK, now on to focus.
Ann wrote:Thanks Misty - I agree about the focus and the skew. I can move the "focus box" around the page before I take the photo and check it on the laptop screen and spend all day getting every bit of it in focus and never get to take a photo since one thing will be out of focus when another part will be in focus.
So, this is actually one of the disadvantages of larger, nicer cameras.

Your camera has a large sensor. This has a couple of side effects, but the important one for your project is that a large sensor makes it easy to have a shallow plane of focus. Photographers call this "depth of field". What it means is the slice of the world that is acceptably in focus when you take a picture. This slice of the world is parallel to the sensor in your camera. That is why in this image, the image becomes less in-focus as it gets closer to the camera -- you are broaching the fuzzy edges of this focal plane.

Here are some example images of shallow DOF, which is only possible with DSLRs with relatively large sensors:
Shallow DOF

Here are two images from HP that demonstrate the effect very well.

Large aperture.
Small aperture.

As you can see, the way to get more of a scene in focus is to use a smaller aperture. Your aperture is set to F/5.6, which is a middle-of-the-road value. Aperture values are a fraction, with the numerator being 1, or "f" and the denominator being the size of the circular hole. Thus f/1.8 is a "large" aperture, and f/22 is a very small aperture. The important thing to remember is that smaller apertures make more things come into focus. After f/11 things can get a little tricky, but it's technical. For your focus issues, I recommend changing your aperture to f/11 and seeing if this out of focus page edge sharpens up:
AMagCoverfocus.jpg
(286.77 KiB) Downloaded 366 times
Now, there's another issue. You can think of the aperture as a "valve" that lets in light. A smaller aperture means that less light gets in. Your camera is already taking pretty "slow" pictures. By this I mean that the shutter is open for a long time. According to your RAW image it is 1/6 of a second. The problem with this kind of slow shutter speed is that it is very easy to blur the image by bumping the table or something. On my portable scanner, the shutter speed of the small cameras is 1/100th of a second, preventing any issues with vibration.

So far, you can correct a few things.

If you put your pages more parallel to the sensor of the camera, you can use a wider aperture, because your DOF can be less.
However, if you need the pages to be skewed to keep the lights out of the image, then you need a narrow aperture to keep it all in focus. You should increase the ISO of your camera to compensate for less light.
A third option, and I think the best option, is to use a lot more lights. More lights = faster shutter speeds and narrower apertures at the base ISO of your camera, which is the best of all worlds.

Ann

Re: Our DIY Scanner

Post by Ann » 07 Jan 2010, 00:52

Hey Dan - please, I welcome all advice and don't assume I know anything about photography, because I haven't done this stuff since high school before there even were digital cameras. The photography I've done since then has all be auto focus stuff whether it be film or digital. I have to re-read what you wrote several times so I get it and compile it with what Misty wrote. What you did with the white balance correction looks great; I've been setting the camera to Daylight, too, and I thought I did with this photo, too. But, from what you wrote, that wouldn't really matter during the photo taking process anyway. Again, I have to re-read what you wrote; I'm going to save that page as a pdf and have my camera manuals open, too, so I can figure out if I understand you. Thanks for going into such detail - it will really help me with my grant sample, which I will probably now re-shoot - maybe.

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Re: Our DIY Scanner

Post by daniel_reetz » 07 Jan 2010, 09:17

Daylight is 6500k, so you were likely close enough, (but yeah, it doesn't matter if you're capturing RAW).

If your images show any out-of-focus stuff it might be smart to re-shoot, but don't re-shoot for the sake of white balance.

If you run into any frustration and you'd rather talk over the phone, PM me and I'll cook up a 612 number so we can chat.

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Re: Our DIY Scanner

Post by Misty » 07 Jan 2010, 10:29

Re: white balance, it does look like her software has been correcting that. Compare her sample image:

Image

to your version:

Image

It looks like the WB is being set accurately after the fact, even if it was wrong as shot. While it wouldn't hurt to set a perfect colour temperature in the camera, as long as it's being corrected properly in software you should be okay.

For the purpose of accuracy, I'd definitely recommend batching all of your raws with the same white balance, Ann. If 6300K is what your lights are, you can use that. It will provide more consistency between your images than using an auto white balance tool.

Edit: On the aperture - if you want to try a small aperture, like Dan recommended, try your camera's Aperture Priority (Av) mode. Basically, what that does is it lets you manually choose the aperture; the camera then automatically chooses a shutter speed for you based on your exposure setting, to get an image of the right brightness.

Edit #2: Though Dan's absolutely right - using a shutter speed that's too slow increases the chances that your camera will move just slightly over the exposure time, resulting in a blurry picture. As an example, take a look at these two sample images I just shot to demonstrate. They're crops from a full-resolution photo of an atlas page. Both were taken on a tripod in the exact same position, in the same session, with the same lighting and exposure setting. I used Av mode, with the first photo having the largest possible aperture at that zoom range (and hence the fastest possible shutter speed), and the second having the smallest possible aperture (and the slowest shutter speed).

Image

Image

Both of these were taken raw, with minimal post-processing and default sharpening settings in ACR. You can see how the second is so much softer - that's because the camera jittered just slightly over the course of the half-second the exposure was taken, blurring the image a bit, while the first had a short enough exposure time that the effect is not visible.

With brighter lighting, I could have afforded to have the aperture as small as possible and keep the shutter speed quick enough that there would be no blurring. Proper lighting will absolutely be a priority of mine when I'm able to build my cradle (which sadly won't be until a new budget comes in). Higher ISO speed will also let you keep shutter speed at a minimum, but on my G10 you pretty much need to keep ISO glued to 80 in order to keep noise invisible. Even on a better camera, it's best to keep ISO as low as you can.

Edit #3: I guess PNG doesn't support EXIF! Here's the relevant settings I used on the two shots.

First: Shutter 1/10; aperture f/3.5; ISO 200
Second: Shutter 0.5s; aperture f/8.0; ISO 200
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.

Ann

Re: Our DIY Scanner

Post by Ann » 07 Jan 2010, 15:36

Thanks Dan - Thanks Misty. Misty - I retook the mag cover photo, so the example you uploaded is the first time I took it, and I did put it through some processing to shrink it from RAW to JPEG, and to get under the uploading limits; the one that Dan uploaded is the second one where I took a bit of time to re-focus it, but has had no editing at all. So, I did something different with both shots. I just skimmed what you wrote; I will need to pdf it, sit down with Dan's stuff, and look at the stats (or I guess, metadata) from the stuff I've shot that I'm using as a test project. I probably won't need to re-shoot anything, although I want to test the different ways I can place the hand-written journal on the cradle to maximize photo size and lessen skew.

Many thanks to you guys - I didn't have the opportunity to play with this stuff last night, but probably tonight. :)

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Re: Our DIY Scanner

Post by Misty » 07 Jan 2010, 16:02

You're welcome, Ann! I didn't have much experience with photography before I began digitizing, so I'm glad to share what I've learned. Let me know if there's anything else I can help with.
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.

Ann

Re: Our DIY Scanner

Post by Ann » 09 Jan 2010, 16:31

Hey - I've done a few tests with written pages like I will be dealing with at the NARA. I tried to customize my WB; it seems I can only do this by photographing something white under the lighting conditions I'm going to use. I did do this and took a bunch of photos - but in the metadata, they all came out as "sunlight" with a WB of 5200K - although the metadata calls this the color temp - am I understanding this correctly? I understood what Dan wrote about color temp and setting white balance, but my camera seems to be combining the two together. So, I switched to manual shooting, kept f11, and changed the shutter speed. The faster I set it, the darker the image in LiveView got and I couldn't see it - the screen was completely black after 1/100; the photo was still taken (since I had focused the image earlier) and when I opened it in Graphic Converter, the images were incredibly grainy and very blue at 1/200. I can't focus the images at these shutter speeds, since I can't see them. I took shots at various exposures, at f11, in shade, sunlight, and daylight - all came out at 5200K - a few samples can be found dropped at:

http://drop.io/c9rsgx7#

My next test is to set it on A-dep to see if the focus is OK and see what the WB does. What bugs me is the LiveView window has the spaces for the WB numbers - it even has a damn big "K" there, and when the Custom WB is "on" - the custom icon appears - I just can't specify a number I want (it is set to the white piece of paper that I photographed when I set the custom WB in the first place) and the manual does have a WB correction section, but it doesn't allow the inputing of numbers like "6300K", and the metadata does address WB but it only says "shade" etc, but it does list color temp as a "K" number. I'm not sure what I'm missing.

Ann

Re: Our DIY Scanner

Post by Ann » 10 Jan 2010, 15:57

I have taken several photos, changing the f-stop, auto white balance, auto depth of field, etc. The best I've come up with, for the hand-written-type stuff I'll be doing now, is setting the camera to Auto-Depth of Field (can't change f-stop or shutter speed), with Auto White Balance (even when I tried to set the WB, it wouldn't let me set it to an actual number that I wanted, although the Digital Photo Professional software that came with the camera DID allow setting the color temperature to 6300K - which I did - but I think that the AWB looks better). I also did a bunch of manual focus, high f-stop, fast shutter speed tests but the A-Dep looks best since the focus is so good over the whole page. So, the file at the link below is Auto-Dep, AWB, 1/6 shutter speed, f5.7. It would be great if I could increase the shutter speed & f-stop with A-Dep, but since it's an auto function...

http://drop.io/wk7bjs6#

Here's the histogram for this image:
3.Histogram.jpeg
3.Histogram.jpeg (10.82 KiB) Viewed 4831 times
Now, I don't know if it is really bad that the white end does hit the right side - or if it matters. So, at this slow shutter speed and lower f-stop, I guess I just have to be careful not to knock things around too much. I may still change the WB in editing, but Graphic Converter doesn't seem to have the fine tuning that I need - it seems to be more of a "click where it's supposed to be white" and it washes out the entire image.

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