Just to clarify. DPI is far from irrelevant to people who print. which is A LOT OF PEOPLE. (or if you are using a RIP) LPI an DPI. How many DPI linearly Make up your LPI. Also the frequency thing is sort of important as well if you are printing to a 4 color press that is using halftones. In a RIP all those things can be adjusted to create better image quality even on a desktop inkjet.
Good explanation here (of 4 color)
http://the-print-guide.blogspot.com/2009/04/rosettes-everything-you-didnt-realize.html
http://the-print-guide.blogspot.com/2009/04/rosettes-everything-you-didnt-realize.html
In a digital single chip Camera every pixel represents 3 DOTs. A pixel represent how ever many dots the software or hardware chooses to use to make up that pixel. (usually 3 or 4(cmyk) or has many as they want or chose. Also refereed to as sub pixel elements or dots. This is also true of your computer monitor. It has a dot pitch each pixel is made up of 3 color dots. The better the monitor the tighter the dot pitch and the closer together the Pixels.
http://en.wikipedia.org/wiki/Pixel#mediaviewer/File:Pixel_geometry_01_Pengo.jpg
http://static5.depositphotos.com/1001655/463/v/950/depositphotos_4634956-Cmyk-dot-pattern-vector.jpg
On Tue, Sep 2, 2014 at 7:12 AM, Jonathan Turner <pictures@xxxxxxxxxxxxxxxxxxx> wrote:
Hi Karl,
Wow, that's a lot of information to chew on... thanks for taking the time to answer my questions so thoroughly, it is much appreciated. I'll think through your answers for a while and may have to come back to you on some of your points...
One point that immediately springs to mind though is about the resizing if the composite elements (kids) - lowering the resolution to match the background image; this is something I'd thought about doing but not how you'd described. I'll try it and see what happens. Until now I've just been re-sizing them to fit into the background 'scene' using Photoshops Transform tool, mostly because I've been placing them in groups interacting with one another at different perspectives within the background image - the finished images are supposed to be tableaux of historical scenes. I'd thought about using a filter of some kind to degrade the quality somehow, to make them match the background, but I guess altering the pixel size of each component would do it just as well if not better.
The other point you made about the 'process' is interesting...starting with a background image size at the final output dimensions. Again, I'd thought about this but until recently we didn't really know what the final print size would be. Also, the file size is so big that my computer can't really cope with them... so I've been starting with the background images as determined by the workflow option in photoshops RAW window (at 12MP, 4256 x 3823, 300PPI) adding my re-sized composite elements (cutout and re-sized with Transform) and then resizing the whole image up to the required print size. This all seemed to go fine until we printed an A3 cropped section from an image at 1600mm and realised the background layer was not holding up, or at least, looked a bit rubbish compared to the composited elements (kids).
I've tried starting with a bigger background image by changing the workflow options in the RAW window to it's maximum (25MP, 6144 x 4088, 300PPI) and this seems to have helped, though there is still the issue with background/composite disparity... so I'll try your suggestion of re-sizing the kids to fit the background quality. Do you think it's still important to start with the final output size though? Or even at a quarter size perhaps?
Thanks again though, and I may have to come back with more questions...!
Just in case you're interested, the gallery who've commissioned this piece of work have based the project on a show they had a year or so ago by a fantastic photographer called Red Saunders. The tableaux we're making are nowhere near as good as his, but have a look at his stuff to get an idea of what we're trying to achieve;
http://www.redsaundersphoto.eu/1647.html
cheers,.
Jonathan
Jonathan Turner Photographer e: pictures@xxxxxxxxxxxxxxxxxxx t: 07796 470573 w: www.jonathan-turner.com
On 01/09/2014 16:14, karl shah-jenner wrote:
Jonathan Turner asks:
(questions that requiring pretty complicated answers, bear with me for this long winded reply, or go to #1 for the short version below ;)
The point about viewing distance is a good point, which Ihadn't really considered.
Viewing distance has a heck of a lot to do with everything in photography, up to and including lens choice when making the image. Wide angle images which look all distorted can look perfectly normal if enlarged to wall sized and you force the viewer to stand 2 feet from the image - similarly a 1000mm telephoto shot which we normally describe as 'compressed' will also look totally normal if printed appropriately small OR you force the viewer to stand a long way back (viewing angle the same).
Also, increasing the image size in 10%
increments is something I'd heard about
before but forgotten. I tried it
actually and I think it was was slightly better.
it should be slightly better, but not much - and if you experiment and start with a clolour swatch you will find it eventually creates patterns - highly undesirable. I illustrated that in the webpage I liked but anyone can test it themselves, upsize in degrees until a blindingly obvious pattern is created. resizing is bot a good way to make things bigger, resampling is much better. As long as the algorithm is appropriate (b-spline, s-spline, triangle, hermite, Mitchell, Lanczoz, Bell, etc etc)
similarly downsizing (as opposed to downsampling) often creates patterns - more often moire .. from unintelligent bit removal.
What you appear to need is some serious upsizing. If this were being sent straight to print without mucxh manipulation, I would suggest you'd be leaving the upsizing to a RIP, something that's been discussed often in the past on this list. However the process of incorporating image elements with differing levels of detail demand a more complicated pathway.
The real issue though is the disparity between the background image and
the composite elements ...
see way down for more on this (#1)
as such I want to try and make the background image the best quality I
can to start with. So, I went back to the original RAW files, and
remembered that you can open them at different sizes/resolutions...at
the bottom of the RAW window in Photoshop you can specify the
dimensions/resolution and Bit depth you want to work with.
Photoshop is weird. I really wish they would stop mixing ancient printing terminology like dots per square inch in (irrelevant) with computer tech - pixels. Your image has a native resolution and if shot RAW it'll be the full sensor size. I will asume it's a 12Mp camera and that'd mean you have something like a 3k x 4k pixel image. dpi is irrelevant BUT photoshop wants to know what sort of silk screen you'll be squeezing your oil based ink through and thus demands to the know the dot pitch frequency (bah) Tell it 300, then check that your image is still only 3k x 4k pixels in size when it opens the image.
Dimensions and resolution I understand,
I apologize if I come across as suggesting you may not - I've found a lot of confusion starts and never gets past Photoshop forcing weird conflicting concepts of 'resolution' on people so I try to define the problem so we're on the same page ;)
though Bit depth is something
I'm unsure about...I have the choice of 8 or 16 bits,
simple answer is 'work in 16 bit'.
Bit depth is like the number of steps between absolutely no colour and total colour. black (no clolour in transmitted) to white (all colour in transmitted) - a bit of basics (sorry!)
if there are 4 steps you have black, dark grey, grey, light grey, white.
traditionally we have 1 bit (1 to the power of 2 or 1^2 = 2 colours.. ie, black/white)
2 bit (2^2 = 4 colours)
4 bit ( 2^4 =16 colours)
8 bit (2^8 = 256 colours) - this is a point where we
16 and above bit gets a bit weird, with some padding bits needed for computational purposes being added in some cases (see here http://en.wikipedia.org/wiki/Color_depth#High_color_.2815.2F16-bit.29 ) but basically for editing, more is better - if your exposure is damned good to start with and you're not going to stretch out the tonal range, 8 bit is fine (no different from shooting E6) - and although their are now printers that apprently work with 16 bit, I've not seen the output and would suggest that while they might 'handle' 16 bit, they may (or may not, I truly have no idea) simply be data converting and still printing using an 8 bit process.
What this is all about is how good our eyes are at perceiving the transitions of colours - remember ever seeing pictures where the sky broke up into distinct bands of colour? Often that was through over-editing or more frequently, using a low bit depth image. If you only have say 16 colours to represent the sky, it'll break up into bands of colour to represent the closest colour available to reproduce the actual sky colour. You don't see this much any more..
However it comes down to, the human eye is hard pressed to see discern 1/256th of a shade of colour difference in an image. ie, 8 bit (256 shades of individual colours) arranged in a line looks like a smooth transition with no idividual patch standing out as being darker or lighter. Actually it is hard pressed to see 50 gradation swatches in mid tones, but eh.. 6 bit colour isn't really that mainstream (64 steps, and we actually can see gradations in tarker tones better than lighter tones)
When it comes to image manipulation however, the more the merrier if you need to wriggles those tones about. stretching out the tonal range is a lot less likely to show banding if you have 65000 gradation levels to expand out compared to 256. I could write 100 pages of explanation but you'll see it yourself if you experiment..
and I'm presuming
if I choose 16 bits it will be better quality,
nope, just more of a gradation of tones between black and white, only of use if you fiddle the levels enough to find banding occurring in 8 bit, and not in 16 bit.
I've tried using it and itcomposite psd the file size exceeds 2gb..
certainly increases the files size...so much so that when I have a final
if I choose a higher resolution setting than
300PPI will that actually increase image quality?
I think you're fighting the Photoshop File Size Mangling Feature - it's been an age since I fought this beast but the essence is that you will probably find you have inadvertently resized the image and added data. Let me see if I can remember howq this fight goes - I saw students doing this often.. It kinda went like: Open a camera image of say 3000x4000 pixels (which the camera may have tagged 72 dpi for some insane reason), change the dpi to 300 (if you don't think this through, your may find your image is now 12,500 x 16,667 pixels - 17x bigger .. {or (300ppi /72ppi) squared bigger). Add a layer to that and it gets worse, all of a sudden you're losing this battle.
300 pixels per inch (ppi) is an acceptable viewing resolution at 'normal viewing distance' (1/2 arms reach) for print - a compromise, a general quality standard. heck, most monitors are only 90-140-ish) (or 72 ppi if you talk of the early macs) At 300 print pixels per inch most people don't see blocks - for some even 100 is OK, but truth is, cut out or blank one line of pixels in an image (or add one line of white pixels) and even at 1200 pixel resolution you'll see it. heck, drop a line from a 4800 dot per inch (dpi) printer with a blocked jet and you'll see it. but that's a line and we recognise repetition (and lines) better than teeny individual dots.
Any good tips for improving overall base image quality much appreciated.
Just to re-cap; the images are composites with a final output size of
around 1600mm x 1064mm.
you're looking at around 64 x 42 inch image. I'll use inches since we're using dpi (ppi) even though I'm a metric person myself.. so the ideal image size that you will be sending to print in pixels is 300(ppi) x 64 inch times 300 (ppi) x 42 inch or 19,200 pixel x 12,600 pixels, or 241 Mp. Something I think may exceed your camera's original output ;)
(#1 - the process)
So basically you are starting off this process by upsizing your image to final print size, preferably using an appropriate upsampling algorithm - save this file. it's big (241 Mp), then forget it for now.
Next we need to discuss 'resolution' in terms of resolving power and not how many image elements exist in a given dimension (which is how resolution is usually discussed in digital photography). and this is the dilema you're facing - you have nice sharp face pictures you're trying to insert on a background that is slightly less sharp and you want it to look natural -
Resolution is the ability of the system to resolve detail. Like say you shoot an image and oh yes, the back looks like a nice white wall in image A, but in image B the camera was able to 'resolve' the background and you notice it's not a plain white wall, it's actually tiled and the individual tiles can be discerned. How it was resolved may be a better lens, less shake, a different focal point, a different aperture - whatever.. it may even have been a different media.. say a finer grained film with higher capacity for resolving (resolution) -
Putting these pictures together is going to be tricky as you know, much as mixing 70mm film and 8mm film would be tricky.. The way to do it is you've got to work to your limiting resolution, ie the background picture. Now you can either do it fiddling about and just seeing what looks right, or you can do it mathematically, or a combination of the two (have a rough mathematical idea and fiddle it from there until, it looks right.. this will probably work best :)
Basically, it's back to the viewing angles!
this will get complicated because of my uncertainty about the original image sizes .. but basically you have a grainy low res background and sharp, high res bods to overlay.. so you need to lower the res on the foreground kids to match the best quality you can get out of the background image!
And i'll warn from seeing many many bad examples of this, mixing camera lens focal lengths can make this a nightmarish task due to the perspective conflicts (see those many actress shots where the photographer used a slight wide and stood close giving her a giant head atop a diminishing body and teeny feet -try putting that on a 'normal' background at your peril!)
Your limit of resolution is your original background image, upsized to 19k x 12.6 pixels. Although this is your final image, you really need to work with the original image size and ratios pertaining to that. I'll assume all images were taken at 3000x4000 (12 Mp)
i'll try doing this with ratios and simple arithmetic ..
Your background let's say is a wall roughly 30 feet long shot from say 50 feet away - I'll assume a camera with a 'normal' focal length and talk no more about the lenses involved. You plan on arranging your 6 (more? less?) kids in front of this. you have a 30 foot long wall made up of 4000 dots, or 133 dots per foot.
how big is a kids face? probably 6 inches across maybe? so you only want that kids face to be 1/2 x 133 dots wide - say 65 dots (pixels) wide. (ie, you should be able to fit 61 faces across your 4000 pixel wide, 30 foot wall. I'm guessing you maybe shot these kids at the same resolution but at maybe 1/4 of the frame width in portrait mode - so they might be 1/4 of 3000 pixels wide, say 750 pixels wide. So you can see you need to downsample these face images in this example quite a lot! 750 / 65 = 11.5.. Which means you want to downsample your original 3000x4000 pixel images to (wait for it) 260 x 347 pixels ! - Now I know that sounds horrendous, but this would match the 'resolution' of both images.
Having determined this I would procede to select the head /body/whatever of each individual kid from the original image at full resolution, cut the non essential image data (the non-kid part) then resample the image down 11 fold rather than cutting out tiny images from the small image. These can then be dropped as layers over your background image (they should be the right size now if you calculated correctly) and all told even though it'll look a little fuzzier than you hoped, the images should match both in size and apparent 'graininess' (resolving power is matched)
hopefully I didnt make a dogs breakfast of the calculations but my inclusion of the methodology should help guide you if I have
-karl
