Photoshop View Magnification

Posted on December 22, 2017 by Andrew Astbury

View Magnification in Photoshop (Patreon Only).

A few days ago I uploaded a video to my YouTube channel explaining PPI and DPI – you can see that HERE .

But there is way more to pixel per inch (PPI) resolution values than just the general coverage I gave it in that video.

And this post is about a major impact of PPI resolution that seems to have evaded the understanding and comprehension of perhaps 95% of Photoshop users – and Lightroom users too for that matter.

I am talking about image view magnification, and the connection this has to your monitor.

Let’s make a new document in Photoshop:

We’ll make the new document 5 inches by 4 inches, 300ppi:

I want you to do this yourself, then get a plastic ruler – not a steel tape like I’ve used…..

Make sure you are viewing the new image at 100% magnification, and that you can see your Photoshop rulers along the top and down the left side of the workspace – and right click on one of the rulers and make sure the units are INCHES.

Take your plastic ruler and place it along the upper edge of your lower monitor bezel – not quite like I’ve done in the crappy GoPro still below:

Yes, my 5″ long image is in reality 13.5 inches long on the display!

The minute you do this, you may well get very confused!

Now then, the length of your 5×4 image, in “plastic ruler inches” will vary depending on the size and pixel pitch of your monitor.

Doing this on a 13″ MacBook Pro Retina the 5″ edge is actually 6.875″ giving us a magnification factor of 1.375:1

On a 24″ 1920×1200 HP monitor the 5″ edge is pretty much 16″ long giving us a magnification factor of 3.2:1

And on a 27″ Eizo ColorEdge the 5″ side is 13.75″ or there abouts, giving a magnification factor of 2.75:1

The 24″ HP monitor has a long edge of not quite 20.5 inches containing 1920 pixels, giving it a pixel pitch of around 94ppi.

The 27″ Eizo has a long edge of 23.49 inches containing 2560 pixels, giving it a pixel pitch of 109ppi – this is why its magnification factor is less then the 24″ HP.

And the 13″ MacBook Pro Retina has a pixel pitch of 227ppi – hence the magnification factor is so low.

So WTF Gives with 1:1 or 100% View Magnification Andy?

Well, it’s simple.

The greatest majority of Ps users ‘think’ that a view magnification of 100% or 1:1 gives them a view of the image at full physical size, and some think it’s a full ppi resolution view, and they are looking at the image at 300ppi.

WRONG – on BOTH counts !!

A 100% or 1:1 view magnification gives you a view of your image using ONE MONITOR or display PIXEL to RENDER ONE IMAGE PIXEL In other words the image to display pixel ratio is now 1:1

So at a 100% or 1:1 view magnification you are viewing your image at exactly the same resolution as your monitor/display – which for the majority of desk top users means sub-100ppi.

Why do I say that? Because the majority of desk top machine users run a 24″, sub 100ppi monitor – Hell, this time last year even I did!

When I view a 300ppi image at 100% view magnification on my 27″ Eizo, I’m looking at it in a lowly resolution of 109ppi. With regard to its properties such as sharpness and inter-tonal detail, in essence, it looks only 1/3rd as good as it is in reality.

Hands up those who think this is a BAD THING.

Did you put your hand up? If you did, then see me after school….

It’s a good thing, because if I can process it to look good at 109ppi, then it will look even better at 300ppi.

This also means that if I deliberately sharpen certain areas (not the whole image!) of high frequency detail until they are visually right on the ragged edge of being over-sharp, then the minuscule halos I might have generated will actually be 3 times less obvious in reality.

Then when I print the image at 1440, 2880 or even 5760 DOTS per inch (that’s Epson stuff), that print is going to look so sharp it’ll make your eyeballs fall to bits.

And that dpi print resolution, coupled with sensible noise control at monitor ppi and 100% view magnification, is why noise doesn’t print to anywhere near the degree folk imagine it will.

This brings me to a point where I’d like to draw your attention to my latest YouTube video:

Did you like that – cheeky little trick isn’t it!

Anyway, back to the topic at hand.

If I process on a Retina display at over 200ppi resolution, I have a two-fold problem:

1. I don’t have as big a margin or ‘fudge factor’ to play with when it comes to things like sharpening.
2. Images actually look sharper than they are in reality – my 13″ MacBook Pro is horrible to process on, because of its excessive ppi and its small dimensions.

Seriously, if you are a stills photographer with a hankering for the latest 4 or 5k monitor, then grow up and learn to understand things for goodness sake!

Ultra-high resolution monitors are valid tools for video editors and, to a degree, stills photographers using large capacity medium format cameras. But for us mere mortals on 35mm format cameras, they can actually ‘get in the way’ when it comes to image evaluation and processing.

Working on a monitor will a ppi resolution between the mid 90’s and low 100’s at 100% view magnification, will always give you the most flexible and easy processing workflow.

Just remember, Photoshop linear physical dimensions always ‘appear’ to be larger than ‘real inches’ !

And remember, at 100% view magnification, 1 IMAGE pixel is displayed by 1 SCREEN pixel. At 50% view magnification 1 SCREEN pixel is actually displaying the dithered average of 2 IMAGE pixels. At 25% magnification each monitor pixel is displaying the average of 4 image pixels.

Anyway, that’s about it from me until the New Year folks, though I am the worlds biggest Grinch, so I might well do another video or two on YouTube over the ‘festive period’ so don’t forget to subscribe over there.

Thanks for reading, thanks for watching my videos, and Have a Good One!

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YouTube Channel Latest Video Training

Posted on December 3, 2017 by Andrew Astbury

My YouTube Channel Latest Photography Video Training.

I’ve been busy this week adding more content to the old YouTube channel.

Adding content is really time-consuming, with recording times taking around twice the length of the final video.

Then there’s the editing, which usually takes around the same time, or a bit longer. Then encoding and compression and uploading takes around the same again.

So yes, a 25 minute video takes A LOT more than 25 minutes to make and make live for the world to view.

This weeks video training uploads are:

This video deals with the badly overlooked topic of raw file demosaicing.

Next up is:

This video is a refreshed version of getting contrast under control in Lightroom – particularly Lightroom Classic CC.

Then we have:

This video is something of a follow-up to the previous one, where I explain the essential differences between contrast and clarity.

And finally, one from yesterday – which is me, restraining myself from embarking on a full blown ‘rant’, all about the differences between DPI (dots per inch) and PPI (pixels per inch):

Important Note

Viewing these videos is essential for the betterment of your understanding – yes it is! And all I ask for in terms of repayment from yourselves is that you:

Click the main channel subscribe button HERE https://www.youtube.com/c/AndyAstbury
Give the video a ‘like’ by clicking the thumbs up!

YouTube is a funny old thing, but a substantial subscriber base and like videos will bring me closer to laying my hands on latest gear for me to review for you!

If all my blog subscribers would subscribe to my YouTube channel then my subs would more than treble – so go on, what are you waiting for.

I do like creating YouTube free content, but I do have to put food on the table, so I have to do ‘money making stuff’ as well, so I can’t afford to become a full-time YouTuber yet! But wow, would I like to be in that position.

So that’s that – appeal over.

Watch the videos, and if you have any particular topic you would like me to do a video on, then please just let me know. Either email me, or you can post in the comments below – no comment goes live here unless I approve it, so if you have a request but don’t want anyone else to see it, then just say.

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Pixel Resolution

Posted on December 14, 2013 by Andrew Astbury

What do we mean by Pixel Resolution?

Digital images have two sets of dimensions – physical size or linear dimension (inches, centimeters etc) and pixel dimensions (long edge & short edge).

The physical dimensions are simple enough to understand – the image is so many inches long by so many inches wide.

Pixel dimension is straightforward too – ‘x’ pixels long by ‘y’ pixels wide.

If we divide the physical dimensions by the pixel dimensions we arrive at the PIXEL RESOLUTION.

Let’s say, for example, we have an image with pixel dimensions of 3000 x 2400 pixels, and a physical, linear dimension of 10 x 8 inches.

Therefore:

3000 pixels/10 inches = 300 pixels per inch, or 300PPI

and obviously:

2400 pixels/8 inches = 300 pixels per inch, or 300PPI

So our image has a pixel resolution of 300PPI.

How Does Pixel Resolution Influence Image Quality?

In order to answer that question let’s look at the following illustration:

Andy Astbury,pixels,resolution,dpi,ppi,wildlife in pixels

The number of pixels contained in an image of a particular physical size has a massive effect on image quality. CLICK to view full size.

All 7 square images are 0.5 x 0.5 inches square. The image on the left has 128 pixels per 0.5 inch of physical dimension, therefore its PIXEL RESOLUTION is 2 x 128 PPI (pixels per inch), or 256PPI.

As we move from left to right we halve the number of pixels contained in the image whilst maintaining the physical size of the image – 0.5″ x 0.5″ – so the pixels in effect become larger, and the pixel resolution becomes lower.

The fewer the pixels we have then the less detail we can see – all the way down to the image on the right where the pixel resolution is just 4PPI (2 pixels per 0.5 inch of edge dimension).

The thing to remember about a pixel is this – a single pixel can only contain 1 overall value for hue, saturation and brightness, and from a visual point of view it’s as flat as a pancake in terms of colour and tonality.

So, the more pixels we can have between point A and point B in our image the more variation of colour and tonality we can create.

Greater colour and tonal variation means we preserve MORE DETAIL and we have a greater potential for IMAGE SHARPNESS.

REALITY

So we have our 3 variables; image linear dimension, image pixel dimension and pixel resolution.

In our typical digital work flow the pixel dimension is derived from the the photosite dimension of our camera sensor – so this value is fixed.

All RAW file handlers like Lightroom, ACR etc; all default to a native pixel resolution of 300PPI. * (this 300ppi myth annoys the hell out of me and I’ll explain all in another post).

So basically the pixel dimension and default resolution SET the image linear dimension.

If our image is destined for PRINT then this fact has some serious ramifications; but if our image is destined for digital display then the implications are very different.

Pixel Resolution and Web JPEGS.

Consider the two jpegs below, both derived from the same RAW file:

European Adder – 900 x 599 pixels with a pixel resolution of 300PPI

European Adder – 900 x 599 pixels with a pixel resolution of 72PPI

In order to illustrate the three values of linear dimension, pixel dimension and pixel resolution of the two images let’s look at them side by side in Photoshop:

Andy Astbury,photoshop,resolution,pixels,ppi,dpi,wildlife in pixels,image size,image resolution

The two images opened in Photoshop – note the image size dialogue contents – CLICK to view full size.

The two images differ in one respect – their pixel resolutions. The top Adder is 300PPI, the lower one has a resolution of 72PPI.

The simple fact that these two images appear to be exactly the same size on this page means that, for DIGITAL display the pixel resolution is meaningless when it comes to ‘how big the image is’ on the screen – what makes them appear the same size is their identical pixel dimensions of 900 x 599 pixels.

Digital display devices such as monitors, ipads, laptop monitors etc; are all PIXEL DIMENSION dependent. The do not understand inches or centimeters, and they display images AT THEIR OWN resolution.

Typical displays and their pixel resolutions:

24″ monitor = typically 75 to 95 PPI
27″ iMac display = 109 PPI
iPad 3 or 4 = 264 PPI
15″ Retina Display = 220 PPI
Nikon D4 LCD = 494 PPI

Just so that you are sure to understand the implication of what I’ve just said – you CAN NOT see your images at their NATIVE 300 PPI resolution when you are working on them. Typically you’ll work on your images whilst viewing them at about 1/3rd native pixel resolution.

Yes, you can see 2/3rds native on a 15″ MacBook Pro Retina – but who the hell wants to do this – the display area is minuscule and its display gamut is pathetically small. 😉

Getting back to the two Adder images, you’ll notice that the one thing that does change with pixel resolution is the linear dimensions.

Whilst the 300 PPI version is a tiny 3″ x 2″ image, the 72 PPI version is a whopping 12″ x 8″ by comparison – now you can perhaps understand why I said earlier that the implications of pixel resolution for print are fundamental.

Just FYI – when I decide I’m going to create a small jpeg to post on my website, blog, a forum, Flickr or whatever – I NEVER ‘down sample’ to the usual 72 PPI that get’s touted around by idiots and no-nothing fools as “the essential thing to do”.

What a waste of time and effort!

Exporting a small jpeg at ‘full pixel resolution’ misses out the unnecessary step of down sampling and has an added bonus – anyone trying to send the image direct from browser to a printer ends up with a print the size of a matchbox, not a full sheet of A4.

It won’t stop image theft – but it does confuse ’em!

I’ve got a lot more to say on the topic of resolution and I’ll continue in a later post, but there is one thing related to PPI that is my biggest ‘pet peeve’:

PPI and DPI – They Are NOT The Same Thing

Nothing makes my blood boil more than the persistent ‘mix up’ between pixels per inch and dots per inch.

Pixels per inch is EXACTLY what we’ve looked at here – PIXEL RESOLUTION; and it has got absolutely NOTHING to do with dots per inch, which is a measure of printer OUTPUT resolution.

Take a look inside your printer driver; here we are inside the driver for an Epson 3000 printer:

Andy Astbury,printer,dots per inch,dpi,pixels per inch,ppi,photoshop,lightroom,pixel resolution,output resoloution

The Printer Driver for the Epson 3000 printer. Inside the print settings we can see the output resolutions in DPI – Dots Per Inch.

Images would be really tiny if those resolutions were anything to do with pixel density.

It surprises a lot of people when they come to the realisation that pixels are huge in comparison to printer dots – yes, it can take nearly 400 printer dots (20 dots square) to print 1 square pixel in an image at 300 PPI native.

See you in my next post!

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