Negative Scanning File Size Confusion

[dr_gn]

All, back in 2020 I had some 35mm negatives scanned. A number of options were listed (original negative format, image size, optimum print size and price).

After discussion, I went for this one on their list:




"Images are saved as .jpg files, which open to the sizes indicated.

35 mm / 25.0 Mb*, Optimum print size 12" x 8"

• Image size when opened. The compressed physical file size is smaller."

Price was 80p +VAT




They sent the files through in a .zip file and also on a USB stick, and they looked ok at a glance, so I didn't think much more about it. Now I want to scan in a significant further amount of negatives, I looked more carefully at the files, and they are of the order of 2.5 Mb each, not 25 Mb.

I queried this and they said that when the file gets opened in Photoshop, "it increases to 25 Mb". I queried this again, and got a vague explanation, but it still seems wrong - I thought that .jpg were compressed files and that they aren't un-compressable? Why would they be?

Also, is it correct to state "image size" in Mb? Surely that's file size, and image size should be in pixels?

When I open (for example) a 2.5 Mb image, it says in the image information that the file size is 2.5 Mb, and the image size is 3655 x 2433.



The company seems reputable, and I'm sure I'm missing something, so can someone who knows more about these things explain the:

• Image size when opened. The compressed physical file size is smaller.

caveat in their price list?

Thanks.

[mcflurry]

Isn't the important factor the scanning resolution and dpi, rather than the size they open up to in a program?

[satans worm]

So scanning can be at DPI , or Megapixels , file size is not relevant

I would however push to have .tiff files as opposed to .JPEG as they contain more details for any photoshop work you might do

I get my 135mm scanned at 20mp , i think the 35mm is the same, if its a one off for printing then you should be able to get drum scans that gives 100mp on a 6X6 medium format film negative!

[dr_gn]

mcflurry said:

Isn't the important factor the scanning resolution and dpi, rather than the size they open up to in a program?

To me, image size (pixels) is what it is, and file size (Mb) is what it is. I can't see how the two terms are interchangeable.

I can only assume that for .jpg, there's a correlation between pixels and file size, so if you multiply the x & y pixels, you get a figure, then there's some other factor that brings it up to the theoretical file size. But I have no idea why that would be right; how can you magically get the same resolution in a smaller file. In the example I gave there'd be about a 3x correction factor to get the pixels to the 25 Mb size, assuming 1b per pixel.

I'm confused...

ETA 1b per pixel, not 1 Mb...probably.

Edited by dr_gn on Tuesday 4th January 13:52

[dr_gn]

satans worm said:

So scanning can be at DPI , or Megapixels , file size is not relevant

I would however push to have .tiff files as opposed to .JPEG as they contain more details for any photoshop work you might do

I get my 135mm scanned at 20mp , i think the 35mm is the same, if its a one off for printing then you should be able to get drum scans that gives 100mp on a 6X6 medium format film negative!

Yes, I asked about .tiff, but apparently they only do .jpg.

I assume cost would go up due to increased file size.

I dunno - I've got hundreds to scan, it's going to cost...hundreds.

The thing is, I've been able to salvage many images that I previously thought were junk, because of things like shake correction and the various other PS tools. It's not easy to judge which can be salvaged and which can't, without going through and trying to find every print of every negative and trying out the dodgy ones. I just want to scan the lot and see what I can do with them.

[Simpo Two]

dr_gn said:

To me, image size (pixels) is what it is, and file size (Mb) is what it is. I can't see how the two terms are interchangeable.

I can only assume that for .jpg, there's a correlation between pixels and file size, so if you multiply the x & y pixels, you get a figure, then there's some other factor that brings it up to the theoretical file size. But I have no idea why that would be right; how can you magically get the same resolution in a smaller file. In the example I gave there'd be about a 3x correction factor to get the pixels to the 25 Mb size, assuming 1b per pixel.

I'm confused

An image file can be expressed as either file size (Mb) or image size (pixels, px). Many people make the mistake that a massive file size equals 'good quality'. Well it may, or it may not. I can take a thumbnail image, enlarge it to 50,000px wide and save it as a bitmap. The file size will be huge, but the visual quality will be completely useless.

In this context, I'd say that image size is far more importance than file size. With JPGs, pixels are NOT directly proportional to file size. The file size is all down to how much, and how well, the image has been compressed.

It's perfectly possible to get a good A4 print from a 2.5Mb file - the main thing is the image size in pixels. Yours are 3655px wide which is absolutely fine if the compression has been done well.

The only beef I'd have is that they promised you 25Mb files and delivered 2.5Mb ones. Whatever they may or may not 'open up to' in Photoshop is irrelevant; normal people don't have Photoshop.

[DavidY]

If you have hundreds to scan, then why not do it yourself. Whatever you buy for the process you can sell on later. You can then decide the resolution (and file format) that you are going to scan at, and also decide whether something is worth scanning before you do it.

Either simple backlight, film holder and macro lens equipped camera or something like an Epson (or Plustek) scanner.

Its quite a slow process but at least you'll get the results that you want.

FWIW I've had better rtesults using a camera and a Macro Lens (as opposed to a flatbed scanner) with 35mm film. I batch convert using the Negatiove Lab Pro plugin in Lightroom

[budgie smuggler]

Simpo Two said:

The only beef I'd have is that they promised you 25Mb files and delivered 2.5Mb ones. Whatever they may or may not 'open up to' in Photoshop is irrelevant; normal people don't have Photoshop.

Well not really because accoring to OP the item he purchased said:

" Image size when opened. The compressed physical file size is smaller."

A 24 bit 3655 x 2433 BMP file will (always) be 26MB.

The reason they have given that rather than the compressed size is because some images compress a lot better than others.

[Simpo Two]

budgie smuggler said:

Well not really because accoring to OP the item he purchased said:

" Image size when opened. The compressed physical file size is smaller."

The reason they have given that rather than the compressed size is because some images compress a lot better than others.

Thanks for the clarification. I think that's vague at best, as they're describing a product the customer doesn't actually get.

When I sold JPGs (processed from RAW) I told customers they would get 'full size maximum resolution JPGs'. Which they did. Whether the file was 5Mb or 7Mb mattered not one jot

[budgie smuggler]

Simpo Two said:

Thanks for the clarification. I think that's vague at best, as they're describing a product the customer doesn't actually get.

When I sold JPGs (processed from RAW) I told customers they would get 'full size maximum resolution JPGs'. Which they did. Whether the file was 5Mb or 7Mb mattered not one jot

Yes I agree, they should just say it's X by Y pixels with JPEG compression at 100% quality setting (or whatever).

[Simpo Two]

I'm not convinced the company really know what they're doing.

First, when they say 'Optimum print size 12" x 8"' what they really mean is 'Maximum acceptable print size'. It will print out smaller equally well.

Second, with 3655 x 2433px (equivalent to a 9Mp camera) to play with, a JPG file can be much bigger than 2.5Mb - they're compressing it more than they need to. Memory is so cheap and broadband so fast that, within reason, file size is rather irrelevant now.

Thirdly, 'I queried this and they said that when the file gets opened in Photoshop, "it increases to 25 Mb". I queried this again, and got a vague explanation'. What the file does at their end is of no consequence, it's what they deliver that matters!

[BrokenSkunk]

Jpeg is a lossy compressed format. In a lossy format, the goal is to remove detail from the saved data that won't be noticed. This allows more compression and gives a smaller file. But in order to achieve this, detail is irrevocably thrown away.

With tools like Photoshop it is possible to tweak how lossy the saved file is, but even at 100% I don't believe that jpeg is loss-less.

If this company won't offer a loss less format (TIFF, BMP, PNG), you should find someone competent instead. I say that becuase if they were using decent software, or had any clue what they were doing, they would understand the differences between the formats and be able to offer lossless files. The fact that they can't means that either they are using crap software & have no control over the compression, that they simply don't understand, or that they do understand & could do better but can't be arsed. Either way, they wouldn't get my business.

I'm not adverse to jpeg. It may be a decent fit for what you want. The problem is that you've no control over the amount of detail that's thrown away when the image is saved.

Lastly, you have said that the images are black and white. B&W images contain much less information than a colour one, so if everything else is equal (same image, same resolution & same compression) then the file for the B&W image will be considerably smaller.

[Mr Pointy]

How much are they quoting? This place charges 52p a slide for 4000dpi TIFF:
https://www.mr-scan.co.uk/slides.html

[dr_gn]

Mr Pointy said:

How much are they quoting? This place charges 52p a slide for 4000dpi TIFF:
https://www.mr-scan.co.uk/slides.html

That's for slides. It says 33p for a .tiff file for 200+ images.

My place charges 80p + vat for .jpg

The only disadvantage is sending them by post with the risk of loss or damage I suppose. The place I used before is about 12 miles away so I could take them in myself.

Cheers.

[dr_gn]

BrokenSkunk said:

Jpeg is a lossy compressed format. In a lossy format, the goal is to remove detail from the saved data that won't be noticed. This allows more compression and gives a smaller file. But in order to achieve this, detail is irrevocably thrown away.

With tools like Photoshop it is possible to tweak how lossy the saved file is, but even at 100% I don't believe that jpeg is loss-less.

If this company won't offer a loss less format (TIFF, BMP, PNG), you should find someone competent instead. I say that becuase if they were using decent software, or had any clue what they were doing, they would understand the differences between the formats and be able to offer lossless files. The fact that they can't means that either they are using crap software & have no control over the compression, that they simply don't understand, or that they do understand & could do better but can't be arsed. Either way, they wouldn't get my business.

I'm not adverse to jpeg. It may be a decent fit for what you want. The problem is that you've no control over the amount of detail that's thrown away when the image is saved.

Lastly, you have said that the images are black and white. B&W images contain much less information than a colour one, so if everything else is equal (same image, same resolution & same compression) then the file for the B&W image will be considerably smaller.

Thanks.

The vast majority are colour, only a relatively few are B&W.

There are a few slides as well.

[Mr Pointy]

dr_gn said:

Mr Pointy said:

How much are they quoting? This place charges 52p a slide for 4000dpi TIFF:
https://www.mr-scan.co.uk/slides.html

That's for slides. It says 33p for a .tiff file for 200+ images.

My place charges 80p + vat for .jpg

The only disadvantage is sending them by post with the risk of loss or damage I suppose. The place I used before is about 12 miles away so I could take them in myself.

RM Special Delivery is pretty reliable, although someone will post saying they lost something when they used it.

I strongly recommend a service that ofer dust & scratch removal as that can save hours of processing.

[dr_gn]

Mr Pointy said:

dr_gn said:

Mr Pointy said:

How much are they quoting? This place charges 52p a slide for 4000dpi TIFF:
https://www.mr-scan.co.uk/slides.html

That's for slides. It says 33p for a .tiff file for 200+ images.

My place charges 80p + vat for .jpg

The only disadvantage is sending them by post with the risk of loss or damage I suppose. The place I used before is about 12 miles away so I could take them in myself.

RM Special Delivery is pretty reliable, although someone will post saying they lost something when they used it.

I strongly recommend a service that ofer dust & scratch removal as that can save hours of processing.

I - obviously - want the best quality starting point possible for messing about in Photoshop, then saving finally as .jpgs (I want to make a photobook where all my old F1 images and scans are in one place). If the scratch removal and grain reduction processing they offer doesn't degrade the quality then I guess that would be the best option.

[BrokenSkunk]

Simpo Two said:

Thirdly, 'I queried this and they said that when the file gets opened in Photoshop, "it increases to 25 Mb". I queried this again, and got a vague explanation'. What the file does at their end is of no consequence, it's what they deliver that matters!

Yup, PS can't recover the data thrown away in the lossy jpeg compression. But it will allow you to re-save an overcompressed jpeg as a massive bitmap file, should you be clueless enough to want to.
Who ever this company are, they don't appear to know what they are doing.

[Mr Pointy]

dr_gn said:

I - obviously - want the best quality starting point possible for messing about in Photoshop, then saving finally as .jpgs (I want to make a photobook where all my old F1 images and scans are in one place). If the scratch removal and grain reduction processing they offer doesn't degrade the quality then I guess that would be the best option.

Get them to do a couple of test scans with & without. D&S removal does make sllight difference to the sharpness but for what I was doing it was well worth it.

[dr_gn]

BrokenSkunk said:

Simpo Two said:

Thirdly, 'I queried this and they said that when the file gets opened in Photoshop, "it increases to 25 Mb". I queried this again, and got a vague explanation'. What the file does at their end is of no consequence, it's what they deliver that matters!

Yup, PS can't recover the data thrown away in the lossy jpeg compression. But it will allow you to re-save an overcompressed jpeg as a massive bitmap file, should you be clueless enough to want to.
Who ever this company are, they don't appear to know what they are doing.

This is what's confusing me: If they're using a compressed file type, how can you then magically get an uncompressed image just by opening it? Some information has been lost during compression, so how can you possibly get it back?

I assume they mean that the file will open to be much bigger than the file size suggests, but it's just a bigger version of a previously compromised scan?