Login or Join Now

Upload your photos, chat, win prizes and much more

Username:
Password:
Remember Me

Can't Access your Account?

New to ePHOTOzine? Join ePHOTOzine for free!

Like 1

What is "image quality"?

Join Now

Join ePHOTOzine, the friendliest photography community.

Upload photos, chat with photographers, win prizes and much more for free!

ade_mcfade
ade_mcfade e2 Member 1014778 forum postsade_mcfade vcard England216 Constructive Critique Points
2 Jan 2013 - 1:18 PM

In another thread someone was referring to "image quality" in reference to night photography using small apertures.

The problem I had in answering the question was the vagueness of the term "image quality".

What does it mean? What factors are involved? How subjective is it?

and happy new year by the way Smile

Sponsored Links
Sponsored Links 
2 Jan 2013 - 1:18 PM

Join ePHOTOzine for free and remove these adverts.

sherlob
sherlob e2 Member 82308 forum postssherlob vcard United Kingdom125 Constructive Critique Points
2 Jan 2013 - 2:11 PM

Good question.

Rightly or wrongly I have always assumed that IQ relates to a number of factors, but perhaps chief amongst them is image fidelity. That is - the degree to which the image produced by a particular camera set up is able to give a truthful representation of what was in front of the lens without distortion or artefact. This is not to say high image fidelity is always wanted, needed, or even a good idea - nor does it account for artistic license - rather it is a measurable element of image quality through various parameters. Hence magazine reviews often specify the introduction of artefact on an image (e.g. noise or chromatic abrasion).

I'd be open to other parameters...

mikehit
mikehit  56295 forum posts United Kingdom9 Constructive Critique Points
2 Jan 2013 - 2:26 PM

Regards the camera I would consider any of the following: dynamic range, tonal/colour accuracy, are any colour channels 'blown', noise, distortions and chromatic aberration, vignetting and artifacts from the processing (in-camera or post processing). Depending on the subject matter, any one can make up for deficiencies in another: some are controllable by the user others are limitations of the camera and/or the lens.

I would say it is very subjective in that a well thought-out subject will distract the viewer from any limitations on absolute IQ. As an example, photos by Bresson and host of his contemporaries would likely be dismissed as 'incompetent' in any club competition nowadays but they have had the luxury of time where people have accepted the subject as transcending image quality.

llareggub
llareggub  4677 forum posts United Kingdom
2 Jan 2013 - 2:31 PM

For me I think image quality should be referred to in terms of technical aspects of images that can be quantified and qualified...

Things like Sharpness, aberrations, smoothness of Bokeh, noise, vignetting, diffraction etc can all largely be measured in one way shape or form and you can arrive at a consensus... Once you start veering into intangible aspects then you end up in an area that can not be measured and one where consensus is impossible to reach, it becomes preferential and we all like different stuff (thankfully) Smile

Everything else is aesthetic quality and that can be argued till the cows come home!

Last Modified By llareggub at 2 Jan 2013 - 2:33 PM
User_Removed
2 Jan 2013 - 2:36 PM

What a question to start off a new year, Ade!!

You are right, of course - image quality is an ill-defined term that may be used to describe a wide range of parameters. So here is my best shot:

Image quality is the degree to which mechanistic camera technique, camera attributes, digital processing, printer attributes and paper characteristics combine to assist the photographer to produce the print he wishes to achieve. In other words - virtually everything that contributes to the final print with the possible exception of the artistic talent of the photographer. (But, then, I ask myself, why exclude that?)

Often, of course, we restrict the range of factors by applying the term "image quality" specifically to only one part or sub-part of the process, e.g. the camera sensor or a particular lens or the inks used in the printer.

...and I am as guilty as the next guy of using the term in an ill-defined and inconsistent manner.

Wink

Edit: In fact, thinking about what I have just written, I guess that I use the term most often to describe factors over which I have no personal control, i.e. contributors to the final quality of my print that are determined by "physical" components of the process - such as the aforementioned camera, lens, printer, etc.

.

Last Modified By User_Removed at 2 Jan 2013 - 2:40 PM
mikehit
mikehit  56295 forum posts United Kingdom9 Constructive Critique Points
2 Jan 2013 - 2:43 PM


Quote: For me I think image quality should be referred to in terms of technical aspects of images that can be quantified and qualified...

Things like Sharpness, aberrations, smoothness of Bokeh, noise, vignetting, diffraction etc can all largely be measured in one way shape or form and you can arrive at a consensus... Once you start veering into intangible aspects then you end up in an area that can not be measured and one where consensus is impossible to reach, it becomes preferential and we all like different stuff (thankfully)

Everything else is aesthetic quality and that can be argued till the cows come home!

I have never seen measurements of bokeh, noise or vignetting. Or am I not looking in the right places?
Even sharpness is debatable: the classic line pairs tells you something about the lens/camera combination but as far as i can tell, gives barely more than guidance as to how the combination will affect the final image of any given subject. An example: on a landscape, very little of the image is in the actual focal plane, so does it matter if the edges are a 'little bit blurred' and how will that affect the viewing experience (if at all). Also, 'perceived sharpness' is dependent on contrast and this can be affected by the lens coatings as well as the subject matter. Back to square one.

Last Modified By mikehit at 2 Jan 2013 - 2:44 PM
llareggub
llareggub  4677 forum posts United Kingdom
2 Jan 2013 - 3:05 PM


Quote:

I have never seen measurements of bokeh, noise or vignetting. Or am I not looking in the right places?
Even sharpness is debatable: the classic line pairs tells you something about the lens/camera combination but as far as i can tell, gives barely more than guidance as to how the combination will affect the final image of any given subject. An example: on a landscape, very little of the image is in the actual focal plane, so does it matter if the edges are a 'little bit blurred' and how will that affect the viewing experience (if at all). Also, 'perceived sharpness' is dependent on contrast and this can be affected by the lens coatings as well as the subject matter. Back to square one.

Sorry I should have said quantified and or qualified, I have certainly seen countless comparisons of bokeh, noise and vignetting in terms of camera equipment, naturally with a modular system like a DSLR or M4/3rds then you compound the technical variables of each module...

Once you know all the technical schlep you can then make an informed decision as to whether the technical short comings will have an adverse aesthetic affect on the type of images you produce.

That is how I view it at least, when I am looking for a new piece of kit I decide my budget then look at the "technical aspects" of everything within my budget and then decide whether or not those shortcoming will make the investment worthwhile, if not I save more pennies for something that does fit my requirements.

mikehit
mikehit  56295 forum posts United Kingdom9 Constructive Critique Points
2 Jan 2013 - 3:19 PM

When you say 'qualify' do you mean in side-by-side comparison to the output from another camera/lens? Or some measure that you can tabulate and compare listings? As soon as you move away from that, there is an element of subjectivity in any comparison: for example even for the seemingly 'easy' test chart data I have to compare images side by side and make my mind up if it is better to me than the image from another camera because I cannot find a standalone number that tells me what I want to know.

Carabosse
Carabosse e2 Member 1139395 forum postsCarabosse vcard England269 Constructive Critique Points
2 Jan 2013 - 3:49 PM

True image quality is a photo which makes you want to look at it more than once - even if it has been taken on a basic camera phone! Wink

ade_mcfade
ade_mcfade e2 Member 1014778 forum postsade_mcfade vcard England216 Constructive Critique Points
2 Jan 2013 - 4:27 PM

a quality image makes you "feel" something

if you work up to the highest level, that's it in a nutshell really.

drilling down into the details, you can list hundreds of factors - but really they all aim at one thing, evoking a feeling.

Could be any feeling you like/need - and all those listed factors contribute towards it. Technically superb shots can leave you cold, blurry messy shots can become iconic - which has the "image quality" ?

Smile

mikehit
mikehit  56295 forum posts United Kingdom9 Constructive Critique Points
2 Jan 2013 - 4:48 PM


Quote: which has the "image quality"

That is like saying a Ford Focus in the hands of Carlos Sainz is a better quality car than me driving a Mercedes SLK. Most people would say that is ludicrous.

When someone says "which lens has the better image quality" or the question as posed in the thread to which the OP refers, I think it is clear that people refer to 'image quality' in the sense of technical limitations of the camera/lens. Yes, you can get all arty-farty and talk about the final image evoking feelings etc but that is (to me) a separate issue. I do agree that a 'low IQ' system in the hands of a creative photographer gives better results than the most expensive high-IQ gear in the hands of a rank amateur but I think most people will look on image quality of the gear as separate to the photographic skill of the photographer.

lawbert
lawbert  71701 forum posts England15 Constructive Critique Points
2 Jan 2013 - 4:53 PM


Quote: For me I think image quality should be referred to in terms of technical aspects of images that can be quantified and qualified...

Things like Sharpness, aberrations, smoothness of Bokeh, noise, vignetting, diffraction etc can all largely be measured in one way shape or form and you can arrive at a consensus..

Everything else is aesthetic quality and that can be argued till the cows come home!

That pretty much sums it up for me....Its a scientific value that only top cameras, glass and well perceived PP will produce

A quality image is something totally different and should never be confused with IQ

Paul Morgan
Paul Morgan e2 Member 1315154 forum postsPaul Morgan vcard England6 Constructive Critique Points
2 Jan 2013 - 5:03 PM


Quote: A quality image is something totally different and should never be confused with IQ

Yep, agree totally Smile

ade_mcfade
ade_mcfade e2 Member 1014778 forum postsade_mcfade vcard England216 Constructive Critique Points
2 Jan 2013 - 5:10 PM

is "IQ" and "Image quality" the same then?

lawbert
lawbert  71701 forum posts England15 Constructive Critique Points
2 Jan 2013 - 5:19 PM


Quote: Is "IQ" and "Image quality" the same then?

IQ is just an abbreviation of Image quality.....

Add a Comment

You must be a member to leave a comment

Username:
Password:
Remember me:
Un-tick this box if you want to login each time you visit.