How does downsizing (scaling down) an image affect sharpness?

Started Sep 17, 2017 | Discussions
Charley123 Senior Member • Posts: 1,166
How does downsizing (scaling down) an image affect sharpness?
1

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

Danielvr Veteran Member • Posts: 6,601
Re: How does downsizing (scaling down) an image affect sharpness?
1

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Still true today!

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Downsizing increases detail (relative to area). But that's different from making sharper - sharpness is the product of detail and acuity. The interpolation process used in downsizing causes adjacent pixels to lose contrast between them. Unsharp mask fixes that.

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

The latter, because it captures more detail, and crams as much of that as possible into the final image (but to bring out that detail, you'll still need Unsharp Mask).

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wolfychi Senior Member • Posts: 1,158
Re: How does downsizing (scaling down) an image affect sharpness?

Charley123 wrote:

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

it is always better to shoot the photo at the highest possible resolution as your camera can achieve, this way some micro details are captured properly, when you reduce the resolution/down sizing the image, hopefully those micro details information would still be part of the overall image, or if you wish to crop instead of down sizing the image to the smaller frame size, the original micro details would be retained as well.

OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

Danielvr wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Still true today!

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Downsizing increases detail (relative to area). But that's different from making sharper - sharpness is the product of detail and acuity. The interpolation process used in downsizing causes adjacent pixels to lose contrast between them. Unsharp mask fixes that.

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

The latter, because it captures more detail, and crams as much of that as possible into the final image (but to bring out that detail, you'll still need Unsharp Mask).

All these years later I don't remember what unsharp mask setting to use. Please advise.

I shoot at 2400 x 3400 pixels (M-SF) for ocassionally printing 8 x 10 at 300 dpi, but I usually scale down to 1280 x 920 for on-screen/Internet display. What unsharp mask setting should I use after scaling down that much?

Paul De Bra
Paul De Bra Forum Pro • Posts: 12,914
I like unsharp mask *before* downscaling, not after.

Danielvr wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Still true today!

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Downsizing increases detail (relative to area). But that's different from making sharper - sharpness is the product of detail and acuity. The interpolation process used in downsizing causes adjacent pixels to lose contrast between them. Unsharp mask fixes that.

...

I'm still a big fan of the old 10DFinisher routine, which does many things, including upscaling (close to the start), a strong unsharp mask, and finally downscaling. It thus performs the unsharp mask before downsizing and I prefer its result over downscaling and afterwards performing unsharp mask to regain sharpness.

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Public pictures at http://debra.zenfolio.com/.

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JakeJY Veteran Member • Posts: 5,404
Re: How does downsizing (scaling down) an image affect sharpness?

Charley123 wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

In Photoshop (at least the version I have) when you can choose Bicubic, Bicubic Smoother, or Bicubic Sharper. They suggest using the last option for downsizing and it automatically applies sharpening already. So if you use an unsharp mask you may be doing sharpening twice.

In even newer versions, the default method is "Bicubic Automatic" which automatically applies the Bicubic Sharper option when downsizing (and Bicubic Smoother for upsizing).

For the most accurate control over how much sharpening you want, you can just set it to Bicubic and do sharpening either before or after.

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Danielvr Veteran Member • Posts: 6,601
Re: How does downsizing (scaling down) an image affect sharpness?
4

All these years later I don't remember what unsharp mask setting to use. Please advise.

That would depend on the specific algorithm used in your specific software. The default value is probably best.

I shoot at 2400 x 3400 pixels (M-SF)

Why? By not shooting at full size you are missing detail, limiting your ability to crop, and not fully using the potential of your lenses.

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obsolescence
obsolescence Contributing Member • Posts: 723
Re: How does downsizing (scaling down) an image affect sharpness?

Topaz Detail (plug-in for PS) gives me much more control, both of how much sharpening I want to apply simultaneously at different pixel radii (with real time preview), independent shadow / highlight sharpening, local control with masking, pre-programmed as well as user-defined presets, and many other options. It takes more time, but I find it can be worth the extra effort. Download a trial version at the Topaz site.

There's a balancing act when working on digital captures between sharpening and noise reduction. This is most easily done in Raw processing by adding judicious amounts of each, and often refining the sharpening in post. Some Raw processors also add "offset" to increase the sharpening toward corners (good for many WA lenses). For very high res captures, I set Threshold to '0'. I avoid excessive sharpening at very small pixel radii because this makes noise more prominent (grainy) especially in shadows and in broad color areas without detail (such as blue sky).

I like to experiment in order to find the right settings, and usually I then back off from that because initially it looks good but then I realize it's too much. I sometimes do the sharpening on a duplicate layer, then mask (filled with black), then erase the mask in the areas I want to sharpen (as mentioned, this can also be done without a duped layer within the Topaz Detail plug-in interface).

I save my sharpened images to a new file with "_shp" added to the file name (before the extension) to identify it, so the original unsharpened file is preserved. Personal experience and monitor quality can affect how we perceive sharpness, so in the future we may want to go back to the original file to perform a different sharpening routine. I have images that I sharpened years ago while viewing on a CRT monitor that now look oversharpened, and I wish I had saved the originals.

Guy Parsons
Guy Parsons Forum Pro • Posts: 39,221
Re: How does downsizing (scaling down) an image affect sharpness?
1

Charley123 wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

It all depends on the program/algorithm used to do the resizing.

In FastStone Viewer there's a choice of methods available.....

Lots of choices. I usually stay with Lanczos 2.

In other programs there may be less or more or different choices available. it takes personal experimentation with all the options to see if there's any useful differences.

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

Always shoot at the highest resolution possible as then your choices are wide. You could take the whole image and resize it later, or you may discover that a smaller crop of the whole images is what you need and thus the crop may already have the right pixel dimensions. Post processing zoom, so to speak.

There's no need to downsize for printing or screen/TV display as the printing or display program usually does a good job of resizing before it prints or displays.

After any resizing further sharpening may be needed and that will depend on how the image is to be used.

Regards..... Guy

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Guy Parsons
Guy Parsons Forum Pro • Posts: 39,221
Re: How does downsizing (scaling down) an image affect sharpness?
1

Charley123 wrote:

All these years later I don't remember what unsharp mask setting to use. Please advise.

Sharpening all depends on the file size and the end purpose of the file and to some extent what the image is all about. Many images I use anything from 2 pixels radius down to 0.3 pixels and vary the amount to get the result that looks OK for the end purpose.

I shoot at 2400 x 3400 pixels (M-SF) for ocassionally printing 8 x 10 at 300 dpi, but I usually scale down to 1280 x 920 for on-screen/Internet display. What unsharp mask setting should I use after scaling down that much?

Always shoot at full resolution and let the printing program do any resizing to give the result you need. Trying to mangle files to fit some sense of "300 pixels per inch" is unnecessary. All cameras now have enough pixels to print to any normal large size. Usually the printer driver is doing the necessary resizing the large pixel counts to fit its own internal requirements.

Internally Epson printer drivers work at 720 dpi and Canon at 600 dpi with variations to that for full bleed printing (borderless).

Better still to use a proper printing program such as Qimage Ultimate that will do auto resizing and auto sharpening to suit the printer type and the size that you are printing.

To save space for email or web display then some downsizing may be needed.

One example is some years back I was playing with 10 inch and 8 inch digital picture frames. To get the best results on those devices I found that I needed to reduce images to exactly twice the pixel dimensions of the frame, raise contrast and saturation above what I would normally use, and use a fairly heavy hand with sharpening. That way the images which may only show for say 5 to 15 seconds or so do have more impact. If printed with those same alterations then the result would not be pretty.

Basically it is all about experimentation and finding what suits you, mindlessly following some "expert's" ideas of settings may lead up a bad blind alley.

Regards..... Guy

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OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

Guy Parsons wrote:

Charley123 wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

It all depends on the program/algorithm used to do the resizing.

In FastStone Viewer there's a choice of methods available.....

Lots of choices. I usually stay with Lanczos 2.

In other programs there may be less or more or different choices available. it takes personal experimentation with all the options to see if there's any useful differences.

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

Always shoot at the highest resolution possible as then your choices are wide. You could take the whole image and resize it later, or you may discover that a smaller crop of the whole images is what you need and thus the crop may already have the right pixel dimensions. Post processing zoom, so to speak.

There's no need to downsize for printing or screen/TV display as the printing or display program usually does a good job of resizing before it prints or displays.

After any resizing further sharpening may be needed and that will depend on how the image is to be used.

Good information thank you. I learned photography in college back in film times in the early 90s. I learned Photoshop in the mid-90s when most of us were scanning negatives, which I think is how/why I learned to capture the image (scan negative) at res/size needed and no more.

My formal photography education is dated prior to digital cameras. That's why I don't know some of these topics very well. I just applied what I learned scanning negatives to my camera settings in my digital camera.

Also, for my first couple of digital cameras, choosing a resolution setting was a non-issue because the cameras had very little resolution. So I left camera on full resolution without giving it any thought because there were no other viable options. That was particularly the case because the cameras were low resolution and I used to print 16 x 20 or 20 x 30 using as much resolution as the camera could muster.

Now digital cameras have a lot more resolution capability and choices, and I don't need as much resolution as I used to (since I make smaller 8 x 10 prints now). So that also increases choices for resolution settings. The problem with many camera settings resolution choices is that I have no formal education for making that choice with a modern digital camera.

So I guessed what to do based on how I used to scan negatives, but it's not transferable knowledge. Some new learning was required.

I've been getting reasonably good results doing what I've been doing, but now I can do better since my education is being updated on this topic.

Thanks everyone

OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

Guy Parsons wrote:

Charley123 wrote:

All these years later I don't remember what unsharp mask setting to use. Please advise.

Sharpening all depends on the file size and the end purpose of the file and to some extent what the image is all about. Many images I use anything from 2 pixels radius down to 0.3 pixels and vary the amount to get the result that looks OK for the end purpose.

I shoot at 2400 x 3400 pixels (M-SF) for ocassionally printing 8 x 10 at 300 dpi, but I usually scale down to 1280 x 920 for on-screen/Internet display. What unsharp mask setting should I use after scaling down that much?

Always shoot at full resolution and let the printing program do any resizing to give the result you need. Trying to mangle files to fit some sense of "300 pixels per inch" is unnecessary. All cameras now have enough pixels to print to any normal large size. Usually the printer driver is doing the necessary resizing the large pixel counts to fit its own internal requirements.

Internally Epson printer drivers work at 720 dpi and Canon at 600 dpi with variations to that for full bleed printing (borderless).

Better still to use a proper printing program such as Qimage Ultimate that will do auto resizing and auto sharpening to suit the printer type and the size that you are printing.

Wow. It's like Boeing 747s exist and I'm just learning of it. I've been doing everything like it was still the Model A car days. Well, I've been doing everything like it was still the mid-90s anyway.

I've been doing good work considering how outdated I am. Many of my old school classic techniques work well with my modern camera, but some don't work so well. It will be nice to update my techniques that need it.

To save space for email or web display then some downsizing may be needed.

One example is some years back I was playing with 10 inch and 8 inch digital picture frames. To get the best results on those devices I found that I needed to reduce images to exactly twice the pixel dimensions of the frame, raise contrast and saturation above what I would normally use, and use a fairly heavy hand with sharpening. That way the images which may only show for say 5 to 15 seconds or so do have more impact. If printed with those same alterations then the result would not be pretty.

Basically it is all about experimentation and finding what suits you, mindlessly following some "expert's" ideas of settings may lead up a bad blind alley.

Regards..... Guy

Thanks

ggbutcher
ggbutcher Senior Member • Posts: 1,486
Re: How does downsizing (scaling down) an image affect sharpness?
1

I'm not a Micro Four Thirds guy, but I saw this one go by in the ticker at the top of the forums page...

To answer the thread title, all image resizing is some sort of statistical transformation of the original pixels, so downsizing in particular loses data.  Upsizing makes new "data", but that's a different question...

So, in downsizing, per-pixel, the essential job is to take a patch of pixels and come up with a single pixel that faithfully represents them all.  This never a perfect result, by definition.  You can find most of the interpolation algorithms in common use described on the web, and the better ones give more weight to the nearer pixels, which improves the result.  But none of them respect knowledge of particular edges in arbitrary directions, and there simply aren't as many pixels in the resulting image to describe the edges, so that's how the reduction in apparent sharpness in the resized image is realized.  This is the state of practice in the editors commonly available, and does not account for current research.

Sharpening after downsize isn't really about sharpening, it's about creating the illusion of it.  What it really does is make the contrast that forms the edge more prominent, which is more appropriately referred to as acutance.  Now, this is just my experience with resizing for the web, typically to 640xAspect, I use USM with minimum radius and minimum strength.  With this application, the overall image acutance is greatly increased.  Any more strength and the edges start to look artificial.  And while I don't have particular data for this one, I don't think there's much benefit to be had in considering a radius greater than the immediately adjacent pixels, comments welcome.

I've coded and used both interpolation resize and USM sharpen algorithms, so that's the basis of my experience.  I haven't coded more complicated sharpening algorithms like Richardson-Lucy, but I'm happy with my results now and don't see the particular need to hurt my head further... again, comments welcome.

My apologies if an APS-C person is considered an intruder...

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Guy Parsons
Guy Parsons Forum Pro • Posts: 39,221
Re: How does downsizing (scaling down) an image affect sharpness?

ggbutcher wrote:

I'm not a Micro Four Thirds guy, but I saw this one go by in the ticker at the top of the forums page...

To answer the thread title, all image resizing is some sort of statistical transformation of the original pixels, so downsizing in particular loses data. Upsizing makes new "data", but that's a different question...

So, in downsizing, per-pixel, the essential job is to take a patch of pixels and come up with a single pixel that faithfully represents them all. This never a perfect result, by definition. You can find most of the interpolation algorithms in common use described on the web, and the better ones give more weight to the nearer pixels, which improves the result. But none of them respect knowledge of particular edges in arbitrary directions, and there simply aren't as many pixels in the resulting image to describe the edges, so that's how the reduction in apparent sharpness in the resized image is realized. This is the state of practice in the editors commonly available, and does not account for current research.

Sharpening after downsize isn't really about sharpening, it's about creating the illusion of it. What it really does is make the contrast that forms the edge more prominent, which is more appropriately referred to as acutance. Now, this is just my experience with resizing for the web, typically to 640xAspect, I use USM with minimum radius and minimum strength. With this application, the overall image acutance is greatly increased. Any more strength and the edges start to look artificial. And while I don't have particular data for this one, I don't think there's much benefit to be had in considering a radius greater than the immediately adjacent pixels, comments welcome.

I've coded and used both interpolation resize and USM sharpen algorithms, so that's the basis of my experience. I haven't coded more complicated sharpening algorithms like Richardson-Lucy, but I'm happy with my results now and don't see the particular need to hurt my head further... again, comments welcome.

Great information, thanks for that.

Interesting is the way Qimage Ultimate does sharpening http://www.ddisoftware.com/qimage-u/tech-dfs.htm and also interpolating http://www.ddisoftware.com/qimage-u/tech-fus.htm

My apologies if an APS-C person is considered an intruder...

Traditionally you will be lined up and shot at dawn. With an M4/3 camera.

Regards.... Guy

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OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

ggbutcher wrote:

I'm not a Micro Four Thirds guy, but I saw this one go by in the ticker at the top of the forums page...

To answer the thread title, all image resizing is some sort of statistical transformation of the original pixels, so downsizing in particular loses data. Upsizing makes new "data", but that's a different question...

So, in downsizing, per-pixel, the essential job is to take a patch of pixels and come up with a single pixel that faithfully represents them all. This never a perfect result, by definition. You can find most of the interpolation algorithms in common use described on the web, and the better ones give more weight to the nearer pixels, which improves the result. But none of them respect knowledge of particular edges in arbitrary directions, and there simply aren't as many pixels in the resulting image to describe the edges, so that's how the reduction in apparent sharpness in the resized image is realized. This is the state of practice in the editors commonly available, and does not account for current research.

Sharpening after downsize isn't really about sharpening, it's about creating the illusion of it. What it really does is make the contrast that forms the edge more prominent, which is more appropriately referred to as acutance. Now, this is just my experience with resizing for the web, typically to 640xAspect, I use USM with minimum radius and minimum strength. With this application, the overall image acutance is greatly increased. Any more strength and the edges start to look artificial. And while I don't have particular data for this one, I don't think there's much benefit to be had in considering a radius greater than the immediately adjacent pixels, comments welcome.

I've coded and used both interpolation resize and USM sharpen algorithms, so that's the basis of my experience. I haven't coded more complicated sharpening algorithms like Richardson-Lucy, but I'm happy with my results now and don't see the particular need to hurt my head further... again, comments welcome.

My apologies if an APS-C person is considered an intruder...

You're not an intruder. My question applies to any format of camera. I do remember being told that resizing and then sharpening image introduces some artificial info that isn't problematic if it's not resized much, but if done too much makes artificial looking images. So based on that line of reasoning, shooting at (or near) the size/res you will use gives the most real photo.

Some sources claim that digital photos don't look real. Certainly there is a rampant amount of this due to various reasons.

Downsizing followed by resharpening is a contributing factor to artificial photos. The arguing point for people is whether this is only a problem when done too much, or is always a problem, with regard to creating artificial pictures (as opposed to real). I'm not saying who's right because I don't know. It may be a matter of opinion there.

Another factor that contributes to artificial looking photos is people artificially bumping up the saturation and/or contrast. I think everyone can agree that's a problem when people do it too much, but some people think it's a problem to do it at all. I'm of the opinion that these changes should be kept to a minimum, if any.

I don't claim to be the best photographer by any means but I have been getting good results that look very natural and not artificial. That's because they are very natural. They had minimal resizing and no sharpening. I didn't touch the saturation, color, or contrast. If I want more color and less contrast on a sunny day, I use a linear polarizer to add real color/saturation. However I can't claim that my pictures are totally natural because I shoot Olympus jpegs. So they're altered by Olympus engine, but at least I try not to add more criticality to it.

One thing that really bugs me is when people artificially add a bunch of saturation and make their photos look like circus posters. Ken Rockwell's scenery photos are disgusting example of this. I know he thinks he's the best photographer in the world, and he does know a lot of things, especially about Nikon. But the character of his scenery photos bears a striking resemblance to oversaturated circus posters. Rockwell's clown posters scenery photos makes me dizzy and nauseous. However, I did take Rockwell's Nikon D3300 settings recommendations and significantly reduce his recommended bump in contrast and saturation to give beautiful photos from my student's D3300. I used Rockwell settings as a starting point and then toned them down to give good looking photos. My photo assistant/student is getting great results now. The Nikon default settings we're too bland, and Rockwell's were too flamboyant. I found a nice compromise of the two that gives photos with beautiful character that I quite like and my student likes as well.

I know a lot of classic photography information, but I'm also outdated. I'm in the process of learning the current information and techniques for digital cameras. I'm going to retain the old methods that still work good while all cherry picking some new methods to add to my repertoire. My goal is photos that appear natural, but look slightly better than reality. I want to make the buildings and landscapes look good and still with a realistic and believable. Beautiful, but not artificial is the look I'm after. My photos are art to me, but to my customers their purpose is to sell high-end real estate. (Well, high end by the small town standards)

I like Sunset Magazine photos of resorts and beautiful scenery. That's what I want to emulate. I especially like their style back in the film days.

ggbutcher
ggbutcher Senior Member • Posts: 1,486
Re: How does downsizing (scaling down) an image affect sharpness?

Charley123 wrote

You're not an intruder. My question applies to any format of camera. I do remember being told that resizing and then sharpening image introduces some artificial info that isn't problematic if it's not resized much, but if done too much makes artificial looking images. So based on that line of reasoning, shooting at (or near) the size/res you will use gives the most real photo.

Without a doubt.  Thing is, unless you're into printing murals, resize is a fact of life.  I chuckle to myself sometimes when I'm oogling the FF cameras, thinking about how I'd take their best effort and glom it down to 640x480 to post on the web.

Some sources claim that digital photos don't look real. Certainly there is a rampant amount of this due to various reasons.

Downsizing followed by resharpening is a contributing factor to artificial photos. The arguing point for people is whether this is only a problem when done too much, or is always a problem, with regard to creating artificial pictures (as opposed to real). I'm not saying who's right because I don't know. It may be a matter of opinion there.

My sharpening tool has only one control, a 0-10 slider. 0 is no-sharpen, 1 is the absolute minimum, and so on.  It's also pretty quick, so I can rock the mousewheel so it jumps back and forth from 0 to 1.  The difference in the resized image quality is striking, particularly for images with lines.  However, if I rotate to 2, the halos start to show up.

It's kinda like that recent study about exercise: Going from sedentary to just the minimum amount of exercise does folks the most good; after that, the marginal benefit decreases.

I know a lot of classic photography information, but I'm also outdated. I'm in the process of learning the current information and techniques for digital cameras. I'm going to retain the old methods that still work good while all cherry picking some new methods to add to my repertoire. My goal is photos that appear natural, but look slightly better than reality. I want to make the buildings and landscapes look good and still with a realistic and believable. Beautiful, but not artificial is the look I'm after. My photos are art to me, but to my customers their purpose is to sell high-end real estate. (Well, high end by the small town standards)

I learned film in the '70s (or so I thought).  I have a computer science background, which helps heaps in understanding digital imaging.  But even with that, some parts are vexing; I'm wrestling with color management right now. To this bear of little brain, the concept of color is hard on its own, and the ICC has helped to make it even more vexing.

The available tools are quite good; they help a lot in abstracting the technology so we can concentrate on making good images.  Personally, I like to understand as best I can what's going on under-the-hood, so I can make informed decisions about how much to ignore it...

Charley123, I think your questions are very good in that respect.

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samtheman2014
samtheman2014 Veteran Member • Posts: 4,571
Re: How does downsizing (scaling down) an image affect sharpness?

ggbutcher wrote:

Charley123 wrote

You're not an intruder. My question applies to any format of camera. I do remember being told that resizing and then sharpening image introduces some artificial info that isn't problematic if it's not resized much, but if done too much makes artificial looking images. So based on that line of reasoning, shooting at (or near) the size/res you will use gives the most real photo.

Without a doubt. Thing is, unless you're into printing murals, resize is a fact of life. I chuckle to myself sometimes when I'm oogling the FF cameras, thinking about how I'd take their best effort and glom it down to 640x480 to post on the web.

42mp down to 0.3 mp

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Jim Stirling

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OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

samtheman2014 wrote:

ggbutcher wrote:

Charley123 wrote

You're not an intruder. My question applies to any format of camera. I do remember being told that resizing and then sharpening image introduces some artificial info that isn't problematic if it's not resized much, but if done too much makes artificial looking images. So based on that line of reasoning, shooting at (or near) the size/res you will use gives the most real photo.

Without a doubt. Thing is, unless you're into printing murals, resize is a fact of life. I chuckle to myself sometimes when I'm oogling the FF cameras, thinking about how I'd take their best effort and glom it down to 640x480 to post on the web.

42mp down to 0.3 mp

It's not sharp. I think all that downsizing softened it up.

draleks Regular Member • Posts: 256
Re: How does downsizing (scaling down) an image affect sharpness?

Charley123 wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

Scaling photos *up* makes them less sharp due to use of interpolation for the new pixels. The effect of scaling down will depend on the specific algorithm. A simple sub sampling will make the photo sharper.

OP Charley123 Senior Member • Posts: 1,166
Re: How does downsizing (scaling down) an image affect sharpness?

draleks wrote:

Charley123 wrote:

Twenty years ago, I remember learning in a Photoshop class that scaling down photos makes them less sharp, and we were supposed to compensate after scaling down by using unsharp mask to restore to original sharpness.

Twenty years later (current times), I've read from a few sources that scaling down makes photos sharper.

Does it make photos more or less sharp? What do I need to know about this topic?

Is it better to shoot photos at the size I'm going to use them at, or shoot them at a higher resolution and then scale them down to the size I need? Why?

Scaling photos *up* makes them less sharp due to use of interpolation for the new pixels. The effect of scaling down will depend on the specific algorithm. A simple sub sampling will make the photo sharper.

What is sub sampling?

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