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Are you ready for this discussion to go off on a tangent? 'Cos I think it will. 
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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That's just rhetorical hyperbole! 
The difficult we do right away...
...the impossible takes slightly longer.
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Quick, someone fetch a cosh!
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Richard Andrew x64 wrote: Does anyone do this?
I've powered my laptops from a DC to AC converter that output a modified sine wave without any problems. Typically the inverters that you can get that plug into the lighter adapter of the car, but also I have a small solar battery charging system that I've used for a battery backup in the past, again, 12 VDC to 120 VAC and plug the laptop supply into that.
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Thanks for the report, Marc. I have also used the modified sine wave to power the laptop in the past and did not notice any problems. But I was just wondering.
The difficult we do right away...
...the impossible takes slightly longer.
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From what I researched when I was looking at UPS'es a few years ago, some PSU's don't like it at all: because the "modified sine wave" is actually a non-symmetric square wave (or worse a "chopped" square wave) I made sure I bought a true sine wave UPS. Which failed far too quickly: the sine wave was fine, the batteries were fine, but when it switched over the 5V / 3.5V / whatever for the processor failed and it turned itself off ... 
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
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Thank you, Mr. Griff.
I'm sorry to hear that.
The difficult we do right away...
...the impossible takes slightly longer.
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Chinese electronics ...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
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I've run into this as well. The real issue with modern power supplies (and any in the last decade or so) is the switchover time.
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A cheap inverter produce a square wave instead of a sine wave.
There are two problems with that.
A. A square wave produces harmonics really high up in frequency which, if badly filtered, can produce a high amount of interference with sensitive electronics. This can have very strange consequences.
2. In most switched power supplies, the input is first rectified and filtered through a capacitor to create a direct current
To produce the same power through a resistive load, the peak voltage of a sine wave is sqrt(2) higher than the peak voltage of a square wave. this means the voltage of the rectified direct current is 0.707 lower than the voltage from a square wave.
So for a switched power supply to create the same output voltage from a square wave as from a sine wave it uses 1.414 times higher current.
This is one reason brownouts break a lot of electric equipment.
So, I would take a good look at the power supply for how LOW voltage it accepts, if that is less than 0.707 of the nominal voltage of the inverter you don't need to worry to much I think, since switched power supplies are not very sensitive to higher harmonics.
Then there are some intermediate priced inverters producing something called modified sine wave, which is looking similar to a truncated triangle wave.
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Thank you, this was a very good post.
The power supply I'm using says it needs 100 to 240 volts. That would definitely fall out of the range you specified. If the inverter outputs 120 volts, then 120 * 0.707 = 84.84.
I think that's not too good, right?
The difficult we do right away...
...the impossible takes slightly longer.
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Not with an el cheapo inverter, but today there are switched inverters producing something like an acceptable waveform for not that much more money.
Or you can buy a 12V power supply for the laptop. Like for example this: Amazon.com: CAR Charger[^]
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I see. Thank you.
The difficult we do right away...
...the impossible takes slightly longer.
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Hi All,
I wanted to opions on slide to digital image conversion, I have the hardware and can convert them to jpgs, some of them are 'quite dark' to quote Mum, I was wondering if I captured them at a higher bit rate 96 instead of 24 and used a different save format I could them use some software (Paint.Net, Hypersnap or something else) to get more definition out of them? Just wondering... (also who thought Slides were a good idea?)
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Slides are awesome. Color negatives are Satan's own creation.
I can't really help you. I haven't scanned many of my slides. I mostly scan B+W negatives.
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Try the "Auto-Level" adjustment in Paint.net, it works quite well to fix the colour balance etc on old photos.
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I scanned ca. 6000 old color negatives with an Epson V500 photo scanner. And some slides. One of the things you can do is a reasonable color/contrast/etc. correction even prior to the scan.
In addition, you can use something like GIMP II (freeware equal to Photoshop) and really fix them up in any manner. What makes this a better route (if the images have any importance to you) is that you can operate on parts of the image, remove dust, scratches, and etc., as you so choose.
Where I work, for a while, I used to have an occasional call for employees to submit really old pictures of themselves which I would restore. The restored images were published in the company quarterly with a "Guess Who?" theme. Restoration can be a lot of fun. (More so, if you're paid for your time).
| Ravings en masse^ |
|---|
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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GIMP! I knew I was missing something... 
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Try GIMP[^], it's free and a good editor.
I'm not sure how many cookies it makes to be happy, but so far it's not 27.
JaxCoder.com
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Just as general advice, don't save them as JPG file - it's a "lossy" compression format, so you are throwing away detail to start with.
Save them as bitmap, or use a lossless compression format like GIF or PNG instead.
When you've adjusted them - and nearly every paint package can do that - then save the "release copies" as JPG to shrink the size, but keep the lossless originals in case of other work being needed.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
AntiTwitter: @DalekDave is now a follower!
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The only options with the el'Cheapo software was JPG & TIFF  ... BMP was my first thought.
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Can BMP handle 3*12 bits? I believe that TIFF has so many options that may be supported or unsupported, there is most likely a 12 bit option there. Question is if your software supports it.
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Paint.net saves as PNG and a pile of other formats - all free.
Software Zen: delete this;
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You shouldn't pack-unpack-pack-unpack too many times, especially if you have set the quality low to minimize the size of the JPEG file.
But then again: Some people judge the quality of compression (whether photos, video or sound) solely based on the file size - disregading both the software creating the file, and the method used, taking for granted that bigger file = better quality. For "natural" shapes, JPEG is actually quite good.
Note one very important thing about JPEG (that also holds for MP3 and AAC audio and MPEG/H.26x video): Compression is not standardized. Decompression is! Two JPEG files may contain very different data streams, both decompressing to very similar expanded images. Two compressors may use very different strategies for creating a data stream that will decompress to the desired result. Simple software just find "something that works"; more advanced software may try out different alternatives, do the decompessing and see how much it differs from the uncompressed input image, and select the encoding that minimises the differences. Or set parameters to reduce losses below a given treshold.
The basic idea of JPEG is that with a point light source illuminating a flat surface, the brightness will vary over the surface by a cosine function. With a distant, "flat" light source like the sun, a spherical surface will receive ligth varying with the cosine of the angle between the light source and the surface normal. A matte (non-blank) surface reflects light in given direction as a cosine function of the angle to the direction of the light. An opaque material, such as a white lamp dome, spreads light in a similar way.
So, cosine distriubtions are very common. A photo of a smooth ball illuminated by a point source (or by flat light) could in theory be reduces to a handful of number describing the intensity and color of the light source, the size and reflectivity of the ball. These numbers are what a JPEG compressor strives to find.
Photos of smooth balls are not that common, so the image is split into quite small squares that "locally" is like a section of a close-to-spherical surface. The first approximation is to assume that it is part of a sphere, and determine, from the distribution of tones, the radius and a possible light source. For e.g. cheek sections of a portrait, even the first try may come very close to the input image. In other sections, like around the eyes, lips etc., the compressor must select the most dominant spherical surface, and then add another surface the same way, so that when the two are added, they come closer to the original. To get even closer, a third elmemnt can be added, a forth, and so on. If you end up with a discrepancy from the original less that the value of the least significant bit (i.e. if the pixel value are integers from 0 to e.g. 2**8 and the packed and unpacked values differ by less than 0.5), you are actually loosing nothing, yet the series required to represent this may be more compact than raw encoding of every pixel.
If a picture contains elements far from natural cosine-friendly curvatures, but e.g. have lots of sharp transitions, then you must continue that series with many elements to reduce the discrepancies. But a good compressor will do that only in those parts where it is required: "Easy" picture parts receive only a small part of the bit budget, to leave more for the difficult parts. It could lead to e.g. the cheek being slightly smoother than in the original image, to make the text parts sharper.
Note that JPEG in fact tries to describe a limited-pixel-resolution image using continous functions over those square picture fragments. If it succeeds, with sufficientl small artifacts, it has in fact recreated an analog, resolution independent model of each fragment, that could in principle be resampled in any resolution before display (assuming that the resampling is done directly on the cosine functions, not on the unpacked raster image).
So, while it is advisable to use an uncompressed format while editing and adjusting the photo, you should not "be afraid of" JPEG as the final format when all work is done - provided that you use a high quality compressor. Lots of people who insist on lossless formats, whether sound or image, fail miserably in blindfold tests where they do not know anything about the file size, method used etc. and are limited to watching the images at a normal viewing distance, without using a magnifier, and without doing a diff between two images. Even if that is granted them, they may be unable to tell which is the original and which is "ruined by compression artifacts".
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You are (or were) a technical writer. Admit it.
Seriously, that is possibly the most user-friendly explanation of the compression algorithm I have ever read. r/ELI5 must love you.
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