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I am a researcher and often have to take photographs of material from microfiche cards.

enter image description here

The problem that I have been encountering is that on non-digital readers, there is a bright lamp behind the screen. Besides the damage to my eyes, it causes the center of the screen to be very bright. It isn't entirely noticeable when looking at it, but when photographing it is easily apparent:

enter image description here

My camera (Canon S95) adjusts the ISO and brightness based on the average for the scene. Since the center is so much brighter than everything else, it darkens the image as a whole. This makes it so the center is not washed out, but it also makes the outer areas extremely dark and difficult to read. It seems that the problem is that the camera only has a single ISO setting; it can't have ISO be set dynamically for all sections of the image.

The images as they come out, look like this:

enter image description here

With images such as these, what is the best way to make them no longer washed out? I have tried using the Photoshop filters for Levels/Curves, and I can get the outer areas to be more legible - but it washes out the center.

enter image description here

How should I approach this problem? What settings should I use on my camera (I am not afraid of manual mode) to take the best photographs in this situation? Is it possible to edit the images with Photoshop afterwards, and if so is there a way to automate this process instead of having to do it for each image?

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    Would it be possible / practical to obtain an 8x10 transparency scanner? That would eliminate the microfiche reader altogether. – David Rouse Sep 26 '12 at 13:13
  • I would do what you can to eliminate the need to take a photo of the reader, and instead use the correct equipment to capture the image. – dpollitt Sep 26 '12 at 23:46
  • I agree. It would be best to use specialized equipment but I don't have access to it, and also many of the research institutions don't allow personal scanners. Would you recommend using HDR? – Jason Sep 27 '12 at 21:40
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As others have already mentioned, a little image processing is a good solution. However, I have two different suggestions

  1. Take a image when only a blank area is on the screen. Set up the camera on a tripod so that all images are taken with the viewer screen in the same position relative to the camera. Then subtract the blank image from the real images. This will go a long way to even out the blooming in the middle. You can see where I did something similar in photographing a whiteboard.

  2. Don't use the microfiche viewer in the first place. It's poor optical properties are at the root of the problem. Set up a little jig with a macro lens to photograph microfiche films directly. Then you can arrange for a nice even background. All pictures should have close to the same lightness and darkness, so one image processing step over each in batch mode should yield nicely usable results.

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This is a textbook example of image processing that we give the students as an assignment. You do a large mean-filter on the images and subtract it, and fix the contrast, maybe even threshold it.. I implemented it in Image View Plus More 2 as a standalone function called "Local Normalisation -> Remove Gradients e.g. from paper". I assume you have matlab and it is very easy to make a script in it with Io= imread, If=imfilter(Io,ones(100,100)), Ir=Io-If, and apply some scaling to If. You can also try medianfilter.

Output from image view plus more 2 - remove gradient: Output from image view plus more 2 - remove gradient

Output using median filter (tools - remove noise - median filter, then edit - operations substract: Output from image view plus more 2 median filtered,subtracted

In both cases make a selection rectangle larger than the text font.

Video Tutorials:

http://youtu.be/6epxr5-Yhnw?hd=1

New:

http://youtu.be/Y5AaYKul-og?hd=1

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  • Imgview+more batch processing interface does not include this tool, so you have to apply it per image, but I can add it as batch processing, if you need it. – Michael Nielsen Sep 26 '12 at 11:42
  • It can now be done as batch processing, and in Image Controls I made a special implementation of "auto levels" that supports "binary" two-tone jobs like this, so it is really easy to enhance it after removing the gradient. – Michael Nielsen Sep 28 '12 at 11:06
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If there is a bright spot, your camera will record it regardless of its settings, I'm not sure if changing the light metering method to center-weighted average will do any help or not.

But since your camera can shoot raw image, I suggest you to shoot in raw and then edit it in Photoshop.

In Photoshop when you use an adjustment layer, click on its layer mask, pick a big soft brush, select black for color and start painting the center of layer mask, this way you can brighten the surrounding area while keeping the center dark, play with the brush opacity and hardness to get what you need. see this tutorial for more information: Making Selective Adjustments with Layers in Photoshop

I don't have Adobe Lightroom currently and I'm not sure if it makes it easier to do the same edit on raw files, perhaps someone else can help you better with that.

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    Good idea, but I'd use a radial gradient rather than a brush. Once the right gradient is established for the mask, you can save it as a separate image, then record an action to apply the adjustment layer, load the mask image and place it as a layer mask, making the whole operation a single click thereafter. – user2719 Sep 26 '12 at 9:08
  • That's a good idea too, easy and fast, but perhaps the action part is only useful if all images have same framing and same bright spot size. – Omne Sep 26 '12 at 10:06
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If you can center the bright spot, you may be able to use an vignette tool. Lightroom can apply this easily, it is usually done to adjust for lens aberrations, but it may work in this case. But certainly, use RAW.

It doesn't appear that Photoshop has this feature. There are tons of tutorials, but I suspect they all seem geared to loosing data, rather than retaining it.

If you don't have Lightroom, download the free trial and see if this works, but use RAW.

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  • the distribution of the light from the spot is not even in all directions, so "vignet" is a bad mathematical model for this case. – Michael Nielsen Sep 26 '12 at 16:57
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    well isn't that special! I guess you could photograph the blank screen and then somehow subtract the two images... – Paul Cezanne Sep 27 '12 at 10:21

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