I am having some photographic slides transferred to CD and I asked for .BMP rather than .JPG format because (unless i am having a blonde moment) I believe that .BMP files are scaleable whereas .JPG files will lose information if I change their size
The man who is sending them to me has replied:
Hi, the output is usually Jpeg which is the standard, I can save them to BMP format but jpeg is the normal standard. BMP is lower quality.
Which would you go for? Anna
.BMP is a lossless format whereas JPG is compressed, BMP is higher quality. JPG quality can vary from close to original to dire depending on the level of compression. The JPG upside is that the file size can be made much smaller than BMP.
tif are uncompressed but can be huge.
how many dots per inch? the more pixels the better quality.
jpg at top quality are almost as good as tif and a lot smaller.
I scan as TIF as high resolution as i can and then play around in gimp before making various jpgs with less pixels for web work.
i seem to remember that BMP have a colour depth of only 8 bits, but i'm probably wrong again!
The book i was recommended many years ago was Photoshop wow
ps i'v just bought photoshop6wow for £3.57 from amazon, looking forward to groking it!
and some mre amazing plaster work pics from anna k?
No bitmap format is truly scalable - ultimately you come down to pixels
- enlarge too much and you will see them, and things will get jaggy. Fractional pixel scalings can also look a bit rough.
BMP is a very simple format that is lossless - i.e. it includes all the information from the scan, but is very inefficient, it stores every bit. This can mean VAST file sizes (i.e. a 6 mega pixels scan would take 18MB or so as a BMP). The oldest versions were also limited to 8 bit colour (i.e. 256 colours), however most software these days will handle 24 bit BMPs (aka "true colour" or 16.7M colours).
JPEG is a lossy format that not only includes compression, but also discards a certain amount of picture information to reduce files sizes. It also handles 24 bit true colour images. If using it for digitising slides, then you would need to specify the minimum compression / highest quality setting to leave you with most future options. At its highest settings the quality is usually adequate for most purposes.
A compromise would be the slightly less common TIFF format using the LZW compression option. This can store lossless images like BMP, but also includes data compression to dramatically reduce file sizes.
Finally, if you need the ultimate in quality from a scan, you might enquire about RAW format. Some scanners can output their raw sample data, this sometimes has more colour depth that which normally fits into "standard" file formats. High end packages like photoshop can often load RAW images and produce the final image for you rather than relying on the conversion done by the scanner software.
Jpeg format is the norm for photographs. It is a compressed format which "loses" some information, but the amount of compression can be tuned and is undetectable at higher quality settings.
Bitmap (.bmp) format is a primitive format that essentially says "blue pixel, blue pixel, greeny-blue pixel, green pixel, green pixel, red pixel, etc". It is therefore quite verbose and produces big files. I suppose it's fair to say that it's non-lossy, but it's not impervious to scaling artifacts and will soon degrade if you scale it up and down a few times.
TIF is the norm for uncompressed photos, although I don't know much about it as a format. In your position this is probably what I'd pick.
Pete
You won't get many high resolution .bmp files on a CD. For example, I just converted a .jpg from my camera straight into a .bmp file. Went from 2.5 MB to 14.4 MB. Scans are likely to be higher resolution so you might only get 8 to 20 on a CD.
Also, download IrfanView. Allows you to do things like rotate .jpg images losslessly (i.e. no further loss from the original .jpg). As well as many, many other things such as convert from .jpg to .bmp or vice versa.
BMP describes a file format which encompasses a wide range of different options, for example the image contained may be 1 bit-per- pixel (black-and-white), 4 bits-per-pixel (paletted), 8 bits-per-pixel (paletted) or 24-bits per pixel (RGB). Only the last of these can be said to be "higher quality" than JPEG (JFIF), and even then there are options in modern JPEG standards for a better contrast range than BMP (e.g. 12 bits of luminance rather than 8 bits) and even near-lossless encoding.
So saying BMP is "higher quality" than JPG is at best a sweeping generalisation and at worst completely wrong.
Richard.
*Poor* scaling may result in things getting "jaggy" or "rough" (I presume you mean 'aliasing') but sampling theory is unequivocal: you can, theoretically, scale an image with an arbitrarily high quality. The limitations you describe, and are indeed frequently seen, are shortcomings of the scaling process used rather than anything fundamental.
Richard.
The key word there being theoretically. The real world tends to be less forgiving.
Within reasonably bounds, decent image scaling algorithms will produce acceptable results. Although being aware of the limitations before you start can prevent you constraining your options too much later.
You can make the "real world" performance as good as you like. I routinely synthesise 32-tap FIR scaling filters which give near- perfect results - in 2D that's equivalent to a 1024-tap filter (compare with 'bicubic' scaling which is equivalent to a 16-tap 2D filter). The reason that programs like PhotoShop don't match this performance is (primarily) the patience of the user; synthesising a bespoke scaling filter 'on the fly' would take longer than most people are prepared to wait.
If you're interested in the subject, here's a paper of mine:
TIF can include compression, but it's a lossless compression. It does make the files quite a lot smaller.
I've just gone through the process of scanning several hundred old family photos. The experience I got from that was that high quality JPGs are quite satisfactory and can be reprinted to A4 sized (or bigger, depending on the original size). Scan at 300 dpi for normal sized prints and 600dpi for the older photos (which may only be 1x2 inches or thereabouts.)
if you're planning to do any processing, scan at 16 bits per colour (48 bit mode) and scan in colour - even if the photo is black and white. Then use photoshop to collapse it down to
24 bit, or monochrome before JPG'ing it.On Mon, 25 Jan 2010 21:10:15 +0000, snipped-for-privacy@googlemail.com (Anna Kettle) wibbled:
No one has said PNG? Those are compressible but using lossless compression (unlike JPEGS) so best of both worlds.
Anything except BMP.
You ought to get a range of images back, typically a set of small "comping" images too. Arguments will always range about what's best. JPG is best for the comps, and a good choice for the ultimate too - so long as the quality settings and compression were set for quality, not for compact size.
Personally I like Kodak PhotoCD. PNG also has some advantages over JPG, but more software makes better JPGs than it does PNGs, at the high-end of things.
TIFF is an utter pain (anything not monochrome is a minefield of incompatibility, and they're huge).
I can bore for Europe on the subject of image metadata. Look into "Dublin Core" if you care.
Indeed, appropriate choice of algorithm makes a huge difference.
I was also being a little more general, and thinking not only about down scaling but also up-scaling and other filtering operations.
For example a pragmatic choice may suggest JPEG over lossless if one can have more usable resolution in the amount of storage space budgeted, and one knows that cropping of small parts of the image prior to enlargement is likely. Alternatively anticipating working at similar scaling, but needing gamma / contrast / sharpening adjustment may favour the lack of JPEG cell boundaries that you get with a BMP.
Indeed, another trade off to be made... (not that the end user gets to make the decision that often these days!)
jpg is a bitmapped image but it is compressed so has less quality than a similar uncompressed bitmapped image.
Ask him for tiff, they are bitmapped too, but are uncompressed.
Be aware of the file sizes though..
for a 35 mm slide done to say 3600x2400 pixels
jpg is anything between 250kbytes and 2.5Mbytes depending on the quality setting and subject. tiff about 24Mbytes
You probably wont gain much by scanning at more pixels unless its a slow fine grained film done under good conditions and is a good scanner.
PS you can go even smaller on jpg but don't think about it if you plan on doing any work on the images.
I would go for tiff BTW
We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember snipped-for-privacy@googlemail.com (Anna Kettle) saying something like:
He's correct in that jpeg is the 'normal' standard for those who don't give a shit and want them done quickly. A full jpeg will only lose 'some', but in most instances (like this) they will be saved as fairly compressed jpegs if on a CD, so that's not much good if you want to retain as much quality as possible. He's talking bollocks about bmp being inferior - possibly confusing it with gif (which isn't too bad, but very slow and very space inefficient. If jpeg and bmp are your only two options, choose bmp and you can manipulate it to your heart's content. Make sure you make a copy before manipulating and if you have the necessary software, convert to tiff beforehand.
I suspect the only reason he's coming out with such bullshit is his a) ignorance or b) trying to save time and can't be arsed with bmp which might involve him actually spending some time on it.
What's primmitive about something that is an EXACT representation of the data?
It's CORRECT to say that it's non lossy.
As will ANY format if you use sub-optimal scaling algorithms.
Obviously, from your description of it.
You may be correct, but why would youo recommend something you admit to knowing little about?
MBQ
Really? What's the advantage over .bmp then?
MBQ
I'd go for someone who has more of a clue.
MBQ
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.