Image Quality

[cjdnzl]

Hello Colin,

there are some drawbacks with resizing when using IrfanView, a program which I like very much.

1. If you apply it to a 16-bit image (say PNG), the resampled output has only 8 bits per channel.

2. People working with colour spaces like AdobeRGB have the problem that IrfanView does not support colour management. In PS you can resize and transform the images to sRGB in one step.

Best regards

Xaver

Munich

Hello Xaver,

Yes, you are right about IV not handling 16-bit images. However, only those with slrs or a select few compact cameras can do RAW files; all others output jpegs which are 8-bit anyway, and I suspect the majority of slrs are used in that mode. Irfanview will save in PNG mode, but it does have only 8 bits.

A 16-bit image is somewhat academic, though, because data projectors and almost all video monitors are 8-bit, and most laptop screens are only 6-bit. 16-bit is useful only when modifying an image; once the image is finalized, 8-bit is adequate for printing or viewing.

Lastly, although I shoot RAW in aRGB with my Canon, I convert to sRGB for most purposes, except sometimes for competition prints, depending on the scene color content.

Kind regards,

Colin

[cjdnzl]

Colin

How about processing the same basic image twice using both methods you describe and post the resuts so we can take a look.

As you can guess, at the size we use these images at 1024 I am thinking you would have a hard job telling the difference, but I would be delighted if you can prove me wrong. I am always looking for an edge on image quality.

Hi Barry,

Well, I didn't expect a competition; I only said what I do, as an alternative to downsizing with Photoshop.

But, for the sake of putting my computer where my mouth is, so to speak, here are two versions of the same image, full of fine detail. One was downsized in Photoshop using Bicubic sharper, and the other was downsized in Irfanview using the default settings. They are both from the same tiff file. The image sizes show the source; 1.11 MB for Photoshop, and and 874KB for irfanview, both are 1024*768, saved as jpegs at level 12. (I wonder if the larger size for the PS image implies more artifacts in the image?)

There's not a lot of difference, but if you push up the images a bit in Irfanview to get a good look, the Irfanview image is sharper than the PS one, at least to my eyes.

Colin

[Ken Cox]

Colin

screen 1024 768

opened both in irfanview

the irf image is 180 dpi

the ps image is 300 dpi

enlarged each with 4 clicks with the + magnifire tool

the grasses right bottom corner on the irfanview img got pretty jaggie compared to the ps image

i could not see any difference at normal magnifacation

maybe if i had some of that yeast toast spread Vegemite to sharpen my vision i could see better

ken

[cjdnzl]

Colin

screen 1024 768

opened both in irfanview

the irf image is 180 dpi

the ps image is 300 dpi

enlarged each with 4 clicks with the + magnifire tool

the grasses right bottom corner on the irfanview img got pretty jaggie compared to the ps image

i could not see any difference at normal magnifacation

maybe if i had some of that yeast toast spread Vegemite to sharpen my vision i could see better

ken

Yeah, there isn't much difference, but as in my first post on this, I find the Irfanview approach is easier and faster, so that's why I use it.

Vegemite - great stuff, but every American I've met that's tried it hates it, and says very uncomplimentary things about its appearance and aroma. It's an acquired taste, I guess.

Regards, Colin

PS: when dealing in pixels, like 1024 by 768, the ppi (not dpi) is irrelevant.

[Barry Beckham]

Well, with the examples you sent, the Infranview one is marginally sharper.

Thanks for the test, see, well worth doing

[Peter S]

Hi Colin,

I have just had a look at your two images and for my money the Irfanview version is over sharpened with the typically bright white effect that this creates. The Photoshop version looks much better. Very similar to Ken's findings. The other thing that interested me was the way in which they appeared on my screen. The Irfanview image scanned from the top. The PS version appeared highly pixelated, the pixelation then decreased in two stages to produce the final result. I've not seen this before.

Kind regards

Peter

[Lin Evans]

Hi Peter,

JPG files may be saved as progressive or not. Progressive scans line one, two, three, etc., and when a progressive jpg loads, especially if it's a large file being viewed on an appropriate browser, you will see the file build from the top down. If not progressive, some browsers wait until the entire file is loaded then display all simultaneously while other browsers display alternate pixels (looks fuzzy) until all are loaded and rather suddenly all becomes clear. Some web designers like progressive because the viewer at least sees "something" happening and knows that the file selected for viewing is actually loading. With some of the older browsers nothing happened at all until the entire file was downloaded from the source to the host computer. On a very large file this means that one "might" assume that they didn't properly select the file and either go away discouraged or click repeatedly on the source which can also cause issues.

On the issue of interpolation - there are myriad interpolation algorithms and some work much better than others depending on the final disposition of the file. What looks good on screen is not necessarily what looks good in print. Also the size you intend to display or print will often determine which interpolation algorithm works best. Photoshop only uses a few (depending on your version of Photoshop) but other programs including Irfanview have a larger selection. Bicubic tends to soften images as they are enlarged. Attempts have been made to counter this with Bicubic Sharper. As images are downsampled they also often loose sharpness as pixels are removed. Lanczos, Pyramid, Various iterations of Bicubic, Genuine Fractals, Spline, etc., are all unique in certain ways. Really good interpolation is akin more to a "black art" than to science because there are so many variables it's nearly impossible to know what will work best in every case. For example - I use variously Canon, Nikon, Olympus, Sigma, Pentax, Sony, Fuji, Panasonic and a number of other digital camera systems. When I'm enlarging for prints I use nearly all the above interpolation algorithms plus a half-dozen others depending on the nature of the files, number of artifacts, presence or absence of an AA filter, etc. There simply is no one single "right" way to do it.

Best regards,

Lin

Hi Colin,

I have just had a look at your two images and for my money the Irfanview version is over sharpened with the typically bright white effect that this creates. The Photoshop version looks much better. Very similar to Ken's findings. The other thing that interested me was the way in which they appeared on my screen. The Irfanview image scanned from the top. The PS version appeared highly pixelated, the pixelation then decreased in two stages to produce the final result. I've not seen this before.

Kind regards

Peter

[Barry Beckham]

As images are downsampled they also often loose sharpness as pixels are removed. Lanczos, Pyramid, Various iterations of Bicubic, Genuine Fractals, Spline, etc., are all unique in certain ways. Really good interpolation is akin more to a "black art" than to science because there are so many variables it's nearly impossible to know what will work best in every case. For example - I use variously Canon, Nikon, Olympus, Sigma, Pentax, Sony, Fuji, Panasonic and a number of other digital camera systems. When I'm enlarging for prints I use nearly all the above interpolation algorithms plus a half-dozen others depending on the nature of the files, number of artifacts, presence or absence of an AA filter, etc. There simply is no one single "right" way to do it.

Glad I didn't read that when I started Digital Photography. I might have given up before I started.

There was me thinking that all I needed was Photoshop or Elements to resize images and to keep things simple.

Probably the best advice to get sharper images, is to hold the camera steady!!

[Peter S]

Hi Lin,

Thanks very much for your explanation.

On a practical level I feel a bit like Barry. I use Photoshop to resize my images make any adjustments and then to get what I consider to be the "right" amount of sharpening. I can't imagine playing around with such a variety of algorithms. I would never be able to make up my mind which one was the best. I find it difficult enough coming to a decision when I have 3 or 4 different virtual copies in Lightroom!

Kind regards

Peter

[Barry Beckham]

If we are not careful we can make a simple part of slide show creation over complicated for the newer user of PTE5.

For example, if someone asks the question what size images do I need for a slide show, it seems pretty obvious from the question that the person is a newer user of PTE.

Under those circumstances isn't it better to just give a basic answer to a basic question. We can forget all about frames and retaining format. They can find all that out a little later, once they have a show or two made.

Isn't is best to just say, use your image editor (whatever they are using) to make your images the same size as your monitor and leave it at that.

Even getting into unsharp mask at this stage may be too much for some, but if we do, we should give some step by step advice on how to do that and what level of unsharp mask is required.

[xahu34]

If we are not careful we can make a simple part of slide show creation over complicated for the newer user of PTE5.

So, what do we learn from this thread:

• We shall shoot images like a professional
  
• Our shows are rubbish if they contain a single bad image
  
• Even resizing is a science in its own.
  

Really a motivation for beginners;-)

Best regards

Xaver H.

Munich

[Barry Beckham]

Xaver

Not sure I understand your point, can you clarify?

[Lin Evans]

Yes, not so much a motivation but more of a caveat to not obsess over the process because even those who make enlargements for a living can't agree on the best way to proceed in every case.

If people knew how much work went on in the labs to make their simple snapshots sparkle they would never attempt film photography. Fortunately, in the past it was more like point the camera, frame the subject, hold it as still as you can and snap the shutter. Then wait a week or so and see what comes back. Sort the good ones to put in an album and throw the rest with the negatives in a shoebox.

I spoke with Ansel Adams many years ago in San Francisco and asked him why over the years several of his famous prints such as Moonrise, Hernandez New Mexico were visually different in different prints? He told me that a full ten years after he snapped the shutter he was still "tweaking" the negative and looking for perfection.

These days, with digital negatives the photographer becomes the lab technician. Leave it to the professionals to obsess over details and just remember the basics: if you downsample your images you "may" want to apply a little USM (unsharp mask) to bring back the crispness especially for images which won't be zoomed. Too much sharpness will cause excessive "sparkle" when you zoom out.

Otherwise, get the size close to that of the average display device and worry more about the aesthetics of your show than the technicals of your photograph and you will be very happy with the results. In a nutshell, "don't sweat the small stuff" - LOL

Best regards,

Lin

So, what do we learn from this thread:

• We shall shoot images like a professional
  
• Our shows are rubbish if they contain a single bad image
  
• Even resizing is a science in its own.
  

Really a motivation for beginners;-)

Best regards

Xaver H.

Munich

[Barry Beckham]

Lin

Summed up perfectly

[xahu34]

Xaver

Not sure I understand your point, can you clarify?

Barry,

For me your position here seems to be a mixed bag (hopefully a correct expression). You present images as kind of prototypes with a quality which a beginner will hardly be able to achieve. John’s position isn’t less demanding. So, if we discuss on this level it may also be allowed to talk about the “higher theories” of resizing. A beginner who is overburdened with resizing will have trouble with the other requirements, as well.

Best regards

Xaver

Munich

[Barry Beckham]

Xaver

By all means, whatever you said I agree

[Peter S]

I suspect that image quality is similar to many other quality issues and obeys the Pareto or 80/20 rule. You can achieve an 80% perfect image (whatever that means!) with relatively little effort. Every extra % above the 80 costs more and more time and follows an exponential curve. As Lin's example from Ansel Adams shows the last % may even take years.

Some people spend their whole lives investigating what to others are minute details and they become world leading experts in their chosen fields, perhaps image sharpening. We need people like this but all I want is a sharpening tool that works for my images. I guess I may have to think again if I started producing very large prints but Photoshop seems OK up to A3.

When we produce an AV we all make many judgments about individual image quality, which images to include in which order, the music to select, the transitions the timing etc etc. We cannot normally afford to spend hours on one aspect. There is however no doubt in my mind that image quality is crucial.

Xavier I wouldn't go as far as saying a single bad image makes a complete show rubbish but I would say the show would be better without that image.

Peter

[Barry Beckham]

I still think the point I am trying to make is being missed.

Image quality is important, but a show will not be destroyed by one out of focus image, unless the author uses that image as the opening one and then the appeal of the show is reduced considerably. First impressions etc !!

The appeal of many of the slide shows I see can be improved tremendously, with just a little thought and a small amount of work. Nothing too complicated or outside the abilities of a beginner. Forget all the claims of elitism, it is just plain common sense. You don't need to be an expert photographer, have a fancy camera or anything else. What I keep saying is just take care of the basics and your show will improve enormously.

I believe in the KIS principle and so do most of the people I come into contact with.

[Ken Cox]

typo

kiss

[Barry Beckham]

typo

kiss

No typo, I didn't want to be rude

[morturn]

No typo, I didn't want to be rude

hehe

[jfa]

I'm with you Barry. KISp

A simple exercise for everyone here.

The next show you watch, (no matter what it is or where it comes from), immediately after the AV finishes ask yourself which is the image you most remember, then which is the second you remember.

The first image, most likely, will be the best in the show and the second will be the worst. Occasionally it may be the other way around depending on if you are a glass half full or half empty person.

My point is if we can lift the less than perfect images up a little in quality in our show the images the viewer will remember will be all good ones.

[Barry Beckham]

John

What a great way of putting it

You never did say what part of Australia your from?

[Ken Cox]

http://en.wikipedia.org/wiki/KISS_principle

ken

[Barry Beckham]

Xaver

Yes, of course your right and perhaps I have been dancing around trying not to offend anyone.

BUT

If we just spent a little more time on the basics, many of the shows would be so much better, more watchable and more appreciated by all who view them. Its a human thing I suppose when we are faced with the marvellous software at our disposal to dip in far ahead of where you need to be. Generally speaking of course.

I always find it amusing that those who are the most technical rarely produce any work. They are expert at all sorts of mind blowing stuff, but all that expertise takes so much time to learn, that it leaves no time to produce something worth while. This was the case in the darkroom and now with digital photography and AV.

Of course there must be some exceptions to this observation, but they are as rare as hens teeth.