Images - Resolution v File size?

[Mark Hancock]

I get asked a lot for high resolution images of my work for publication, so I got some of my slides rescanned at 1200 dpi digital files. I'm then told it larger files that are required and they don't seem concerned about the resolution. #-o Can anyone explain in simple terms what it's all about?

 

[Sporky McGuffin]

Only thing I can think of is that they don't need uber resolutions but want as little compression as possible?

 

[CHJ]

Only thing I can think of is that they don't need uber resolutions but want as little compression as possible?

+1, it's the only thing I can think of.


Have you asked them what file format they want.

An average .JPG file of a 3468 X 2736 pixels image at 90% is about 1.75Mb.

The same image as a .BMP or uncompressed .TIF is 28.5 Mb.

 

[RogerP]

I always scanned at 4000 dpi using a Canon CanoScan US 4000 slide scanner. The resultant files were 6000x4000 and about 24mb. Maybe something like that is what they want?

 

[bugbear]

I get asked a lot for high resolution images of my work for publication, so I got some of my slides rescanned at 1200 dpi digital files. I'm then told it larger files that are required and they don't seem concerned about the resolution. #-o Can anyone explain in simple terms what it's all about?

For a slide scanner (as opposed to a flatbed scanner working on A4 paper) that's quite low resolution - a slide is 36 x 24 mm,
which is 1.41732 x 0.944882 inches; at 1200 DPI that's 1700 x 1133 pixels.

A typical smartphone at the moment is around 5-8 Megapixels; 6 megapixels is typically 3032x2008, around twice as much.

BugBear

 

[RogerS]

Mark...I think you will find that they are concerned about resolution....just that they are not articulating it properly. 1200 dpi is simply not high enough resolution...RogerP has hit the nail on the head.

You could try your local camera club..

To give you some idea as to what can be achieved, I sent some slides to a friend who scanned them in on an incredibly high resolution scanner. You can zoom in on the digital image to almost see the hairs on the back of someones hand.

 

[Rhossydd]

This is a subject that causes a lot of confusion and there's lots of poorly written information about it on the web. Even many people in publishing that ought to know better don't really understand the issues and ask for the wrong things.

So here's some simplified information that might help.

Image size;
The actual dimensions of the digital bitmap image in pixels, eg 2000 x 3000

File size;
The amount of data the need the image takes up in storage, eg 10kb, 3mb, 50mb etc.
This really isn't important in defining an image or it's quality as it will depend on many factors about the image's size and quality settings, as below.

Format;
This can be divided into two; Image format and file format.

Image format;
Each individual pixel can be defined in many ways. Most usually as an RGB image (ie how much red, green and blue is needed to define the colour), that can be further defined as either an 8bit or 16 bit format defining higher levels of colour accuracy.
In publishing they also use CMYK (cyan/magenta/yellow/black) again in both 8 &16 bit.
Monochrome can also be defined as 8 or 16 bit too.
16bit images are twice as big as 8bit and won't be needed for publication.

File format;
There are many different image file formats, but the most common are JPG and TIFF.
Either can be compressed to save space. The process of compression can be either lossless or lossy. In the former the image will always be exactly the same, with lossy compression varying amounts of data(ie image quality) are sacrificed to save space.
When done carefully lossy compression can be effectively invisible, when done aggressively it can almost destroy the image entirely.
Most good image editors allow varying amounts of compression to be set and you should be told what the resultant image size will be and, hopefully, see a preview of the effects of compression. make sure you check this yourself.

For most real world uses you need to know what image size is required and a quality setting eg lossless TIFF or JPG at 70% either of which would be of publication standard.

Another issue is colour management, but unless told otherwise and know what you're doing, stick to sRGB.

How to scan film is a subject whole books have been written about. 1200dpi (more correctly ppi) shouldn't really be regarded as 'high resolution'. That starts at around 4700ppi and is best with drum scans at 10,000ppi or above, but that's another level of quality that's only applicable for really high quality originals.
Only a very few flatbed scanners can deliver really good results for publication, scans really ought to be done with a dedicated film scanner.
Good film scans are expensive and take a lot of skill and time to deliver the best results.

I should add here that resolution is a bit of a weasel word that is miss-used and misunderstood by far too many people and is used differently in different contexts.

For scanning this ought to refer to the density of samples optically scanned. Some flatbed scanner manufacturers have used the trick of software interpolation(ie the software increases the image size by making up intermediate data) to enhance the specifications of their products beyond their actual capabilities.

Resolution is also sometimes used to wrongly describe an image's property.
Saying an image is 300dpi really isn't helpful, the only important information is it's size in pixels.
This is an old hang over from the very early days of digital imaging when the only output option was offset printing, but really has no place in the current world of multiple output options.

A final note just for completeness;
The term resolution is also applied to printing, here the difference between pixels and dots becomes important, and frequently miss-termed.
Each individual picture element(pixel) is printed with a matrix of very tiny dots of different coloured inks, the number of dots that the printer lays down and their size will effect how each pixel looks. For a home inkjet printer this could be 600dpi, 1440dpi even 2880dpi The differences can be very subtle.
What really matters is the image's resolution. In particular, in relation to print size.

You need enough pixels to look good in print.

At normal reading distances;
300ppi will look excellent in a digital print.
175ppi will look acceptable in a book or magazine.
This assumes that you have good originals.

 

[Mark Hancock]

A big thank you to all above. I am somewhat clearer as to what's required so I'll look into getting the slides rescanned at a higher resolution.
Cheers.

 

[bugbear]

A big thank you to all above. I am somewhat clearer as to what's required so I'll look into getting the slides rescanned at a higher resolution.
Cheers.

It may help to think, not in terms of scanning, but in terms of the final use the magazine will make
of your picture.

The image is (at most) going to be around full page width, and half a page deep.

This (in a normal magazine) is around 8 inches wide and 5 inches deep.

Magazines (not "fine art" ones) tend to need around 400 pixels per inch. This is the printed resolution.

So our 8x5 image must have at least 400*8 x 400*5 == 3200 x 2000 pixels.

Now, if the original image were a photographic print from Boots the chemist, and was 6x4 inches, we'd need
to scan this (on a flatbed scanner) at around 3200 / 6 ~= 600 DPI to get enough pixels. This would give 6*600 x 4*600 == 3600 x 2400 pixels, clearly "enough".

If the original image were a 35mm slide, 1.4 x 1 inches, we need to scan the slide at around 3200/1.4 ~= 2400 DPI, giving 1.4*2400 x 1*2400 == 3360 x 2400 pixels.

If the master is a digital photograph, resolution has no real meaning, you just need "enough pixels", around 6 Mp.

(technically, a photograph does have a resolution, relative to the subject, but this is rarely a useful concept).

BugBear

 

[ChrisR]

:? :? #-o

Far too complicated for my old brain.
Will leave it for the younger generation to worry about. :roll:

Chris.

 

[gregmcateer]

:? :? #-o

Far too complicated for my old brain.
Will leave it for the younger generation to worry about. :roll:

Chris.

=D>

Yet I fully appreciate the trouble the earlier posters went to in order to explain it - I am confident I have already forgotten the detail, but at least 'know' it somewhere in the back of my brain, (and further forward in my brain, still remember to check on ukw whenever I need to know the answer to something!!)

So;

 

[Rhossydd]

Far too complicated for my old brain.
Will leave it for the younger generation to worry about

My post above gives pretty detailed information for people like Mark who need to deal with professional publications, but a lot of it needn't bother people with day to day photography.

The problem is that if you want to post photos here or maybe get photos printed by someone else, unless you take some interest in it you'll get disappointing results.
A bit like taking up scroll sawing and not bothering to use the correct blades, then wondering why your results are always rough round the edges, you can't cut where you want and you keep breaking blades.

 

[Alexam]

Hi Mark,
You can get a free editing photos software called- 'Paint'. If you double click on your image it will be opened in Paint and look very large. Double click on 'Resize' and it will bring up a panel with various options to change the image either in pixels or persentage. If you are on persentage and change the 100% to 20%, that will reduce the image you see to a much smaller size. Then double click on the top left down arrow and you then have a screen that allows you to save or print etc. If you click on 'save as' it will bring up the location where it originated and you can give it a name and identify it as a small image (R) for reduced or S for small - whatever you like. You than finish up with the original image and the reduced image. The reduced image can be posted on line or wherever.

Thats for Paint, but other image software will do similar things. Try whatever you have , or download thr free Paint.

Malcolm

 

[ChrisR]

Far too complicated for my old brain.
Will leave it for the younger generation to worry about

My post above gives pretty detailed information for people like Mark who need to deal with professional publications, but a lot of it needn't bother people with day to day photography.

The problem is that if you want to post photos here or maybe get photos printed by someone else, unless you take some interest in it you'll get disappointing results.
A bit like taking up scroll sawing and not bothering to use the correct blades, then wondering why your results are always rough round the edges, you can't cut where you want and you keep breaking blades.

I curse the day I dismantled my darkroom and gave away all the equipment, including two professional enlargers, exposure meters, timers, plus a van load of ancillary equipment.
That was real photography, which I fully understood, and earned money at, why, because it was logical.

I mistakenly thought digital was the future, the way to go, but how wrong I was, to get the best out of digital photography, is very little to do with good photography, it is being a computer wizard, which despite many hours of trying, I just don’t get. :?

As I said in another post recently, I have two very good DSLR’s and a number of lens just gathering dust. The reason they are gathering dust is that I see little point in taking loads of images if I am unable to do anything with them.

As said I will leave it for the younger computer savvy generation to worry about.

Chris.

 

[bugbear]

Far too complicated for my old brain.
Will leave it for the younger generation to worry about

My post above gives pretty detailed information for people like Mark who need to deal with professional publications, but a lot of it needn't bother people with day to day photography.

The problem is that if you want to post photos here or maybe get photos printed by someone else, unless you take some interest in it you'll get disappointing results.
A bit like taking up scroll sawing and not bothering to use the correct blades, then wondering why your results are always rough round the edges, you can't cut where you want and you keep breaking blades.

I curse the day I dismantled my darkroom and gave away all the equipment, including two professional enlargers, exposure meters, timers, plus a van load of ancillary equipment.
That was real photography, which I fully understood, and earned money at, why, because it was logical.

I mistakenly thought digital was the future, the way to go, but how wrong I was, to get the best out of digital photography, is very little to do with good photography, it is being a computer wizard, which despite many hours of trying, I just don’t get. :?

As I said in another post recently, I have two very good DSLR’s and a number of lens just gathering dust. The reason they are gathering dust is that I see little point in taking loads of images if I am unable to do anything with them.

As said I will leave it for the younger computer savvy generation to worry about.

Chris.

Choice of subject, lighting and composition are still the main elements of a good photo.

Film versus digital is as nothing compared to that, any more than plate vs medium format, medium format vs 35 mm etc.

BugBear

 

[Rhossydd]

That was real photography, which I fully understood, and earned money at, why, because it was logical.

Ah those rose tinted glasses looking backwards eh ?
The rigid strictures of being stuck with fixed film speeds, the difficulties of getting chemical processes controlled, stuck with limited options and reduced colour palettes, the thrill of dangerous chemicals, the silly costs, the delicate emulsions that are so easily damaged forever, the excitement of one mistake ruining huge amounts of work. Oh yes, how wonderful it all was, NOT.

digital photography, is very little to do with good photography, it is being a computer wizard,

Absolute tosh. The core skills of great photography are just as important.
Composition, timing, lighting ,exposure.

Digital photography is as complicated as you want to make it.
Lots of people make fantastic good images with no great computer skills.
I've seen good books made with just photos shot with phones.
Those that can be bothered to learn, or convert their analogue skills and knowledge, can now deliver stunning images of huge technical quality that was beyond the realm of most professionals in analogue days.

 

[mseries]

I mistakenly thought digital was the future, the way to go, but how wrong I was, to get the best out of digital photography, is very little to do with good photography, it is being a computer wizard.

Digital photography is here, it's the present, it was the future back then. The award winning photographers at work are digital. Being a computer wizard doesn't make one a good photographer either.

 

[DiscoStu]

not sure where you are sending them but they should be able to give you a spec of what they need. In reality most publications have no idea what they really need and ask for far higher specs than they use. A newspaper I know used to ask for 1200 dpi images and then printed them at about 120dpi. A lot of news papers use a system where you put you file in and it sends it to the paper at their spec.


Sent from my iPhone using Tapatalk

 

[galleywood]

Chris R

Have you considered attending a suitable 'computer course' to help get you back to enjoying your photography - in digital format?

 

[petermillard]

If you're scanning film for print reproduction, a good general rule of thumb is to get a 20Mb uncompressed original file, as this will cover 98% of common usage - double-page spread in a quality magazine, book jacket wrap-around, poster-sized photographic prints, billboard posters, etc.. etc.. The other 2% of use-cases are obscure enough that the people involved in them should know what to be asking for!

FWIW I was a professional photographer for 20-odd years from the early 80s, so experienced the transition from film to digital at very close quarters; compared to film, digital is an absolute dream to work with - though it ultimately proved to be very bad for business.

Anyone care to guess what my first professional digital camera* cost me in 1996?

Pete

* actually a digital camera back - you needed a medium format camera body to attach it to and it was tethered to a desktop computer.