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I wish to purchase a high resolution photograph of an old painting to project and copy. The images are either in TIFF format, which is 148.8 mb, or JPEG, 24.3 mb. Would either of these give me the resolution found in virtual art galleries, where you can see the brushstrokes and close detail? I wish to copy the painting.

  • TIFF is a CONTAINER format. Like any other container that does not dictate it's contents or their quality - a bottle for example carries liquid that could be water or something very different. Valid TIFF contents range from FAX (1-bit mono with lossy compression) and upwards 48bpp CMYK uncompressed. What format is the TIFF you're looking at purchasing? – James Snell Aug 7 '15 at 14:00
  • In addition to the implied lossyness of jpeg, are they the same specs? Jpeg is limited to 8-bit samples. A TIFF saved from Photoshop after working on the scan might be, in recent years, using 16-bit primaries and a bigger collor space. – JDługosz Aug 8 '15 at 4:43
  • Have you found the information you were looking for or have you precisions to add so we can ellaborate more detailed answer ? – Olivier Aug 9 '15 at 19:55
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I will start by a parallel with printing photos. Having a resolution of 300 ppi (pixels per inch) is relatively standard. It means that 300 pixels of a digital picture will be printed on one inch. It is common to assume that details are conserved with this resolution.

So if the original painting is about 30*21 inch (like the Mona Lisa), you will need the equivalent of 30*300*21*300 pixels = 56.7 million pixels which is a relatively big picture (as modern camera images are around 20 million). Now if each pixel is coded on 24 bits (8 bit per channel, a channel being red, green or blue), the uncompressed file size should be 56,700,000*24 = 1,360,800,000 bits = 162 MB.

As you can see, a lot of assumptions are required to estimate the uncompressed file size: original painting size, color depth (precision of the color - here 24 bits per pixel), ppi needed in regard of the level of wanted details.... Moreover, JPEG allows different levels of compression and its performance depends on the image. => We can't say much without more information.

If it's difficult to have more information about the 2 options you have and assuming money and disk space are not a factor, my advice will be to go for the TIFF (you can always convert it to JPEG later). If there is a significant price difference and if the original picture have similar dimension of Mona Lisa, the JPEG should be enough for your need (more about it in the last paragraph).

For your information, my grand mother has only used JPEG to reproduce painting so far and even with a few MB JPEG, you can see the brushstrokes (try with Google image search).

If you want to know the difference between JPEG and TIFF, you can start here: Should I save an image as png, jpeg or bmp?

By the way, I assume that both images have the same resolution (pixels per inch) but that the JPEG file is smaller thanks to the compression. Indeed, a compression ratio of 10 to 1 going from TIFF to JPEG is common with pictures and usually provides an image of "high" to "very high" quality. In your case, you have a ratio of about 6, which should ensure a high quality.

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From the info you are providing there is no way to know.

Some hints

  • There is no way of knowing the resolution from the file size.

  • Presumably both files have the same resolution (width x height), they are just delivered in different file formats.

  • A high quality JPEG file has a very low information loss, (less than 0.4% compared to the uncompressed 24 bit file). That is way less than a human eye can perceive. So it is a good option.

  • If this is a one time project, buy the TIFF.

  • If you are doing that kind of project every day, and storage could be an issue, I think you will find no problem using the JPEGs.

No way to know the detail

We do not know how big is the original painting. Is it a wall sized one like Las Meninas, or a small one like a Rembrandt portrait? There is no way to know what level of detail you will have.

  • How can a jpeg have 0.4% loss when the color channels are subsampled regardless of what quantization matrix you used? – JDługosz Aug 8 '15 at 4:31
  • The data diference of a well compressed jpg file is just some pixels with less of 1/255 value. This is probably some shift from lets say 255,255,255 to 254,255,254. If you divide this 1/255 it is 0.003921568627451. or 0.39215% – Rafael Aug 8 '15 at 8:02
  • So empirically, the number of munged pixels values. My experiments, some years ago, with "virtually lossless" (don't intentionally discard information by quantizing) worked well on photos with high resolution, as all the channels are 'soft' and have gradual changes, anyway. After looking things up yesterday, I suspect that the subsampling is optional, but don't know if that's true for standard jpeg (jfif) files or how to convince a program not to do that. This gets 4:1 compression on landscapes, while lossless png got 2:1. – JDługosz Aug 8 '15 at 10:47
  • Hmm, you mean on average every sample was off by one? – JDługosz Aug 8 '15 at 10:48
  • Here is an old study I made some time ago. It is in spanish but it is very visual. google translate could help. otake.com.mx/Apuntes/PruebasDeCompresion2/… and yes, the maximum quality on that time was achived by Photopaint and the diference in some pixels (not all), was off by less than one actually, considering that in some cases not all the channels were off. Probably that "generic" .4% is too high. But I would need to make a more methodical explanation, which is by the moment unnecesary. – Rafael Aug 8 '15 at 16:33
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As everyone has noted, the file tyoe is not sufficient information. Find out

  • resolution
  • color space

And the more varied details that could be a TIFF, e.g. if it's made for printing press then it could be CMYK set up for whst publishers want;

  • color model (rgb? Cmyk?)
  • bits per sample

Also, if the jpeg is "just" the same file exported, it can still be worse off than other answers noted. If you look at the Photoshop save-for-web, you'll see "blur" as one of the parameters. So, even if they did not reduce the resolution and used a very high Q setting, you will have the color information cut in half, and may have blurring added to improve compression and hide artefacts, and may have the color space reduced to sRGB.

If the price is the same, get the TIFF. You can save it yourself as a smaller file if needed, using options of your choosing.

These days, storage is not a problem and 150MB is not significant, with hdds (I was just pricing backup drives) at $30 per TB, or 0.45¢ for the file.

Also, you can re-save as a lossless image using PNG or various compression options of TIFF, and cut the file size in half compared to an old-style completely uncompressed file.

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JPEG is a "lossy" compressed format, and it depends if the image is very homogeneous or not, very homogeneous images have a large compression factor meanwhile non-homogeneous images have a small compression factor. On the other hand TIFF is almost always used as a lossless format.

  • Actually, there are some aplications than can use a Lossy jpg compression inside a Tif. I don't see the point of that, but we live in a strange world. – Rafael Aug 6 '15 at 21:54
  • @Rafael Given the differences in file size, that doesn't seem to be a factor in this case. – mattdm Aug 6 '15 at 21:58
  • TIFF can also losslessly compress a picture : photo.stackexchange.com/questions/10906/… – Olivier Aug 6 '15 at 22:30

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