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I've been reading a lot about image sharpness lately. The only thing I haven't seen discussed is photo size. I know that when you zoom in on a photo, it becomes pixelated quickly. So would the opposite also be true? Say a 2000 by 3000px photo is reduced to 1000 by 2000px. Would the smaller image appear to be sharper?

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Say a 2000 by 3000px photo is reduced to 1000 by 2000px. Would the smaller image appear to be sharper?

No. Sharpness is limited by the display's resolution -- the number of pixels per inch. If you want to increase the make the displayed image seem sharper, you need to increase the display resolution. You can (sort of) do that not by making the image smaller, but by backing away from the display so that the pixels appear smaller. Or, you can get a display that actually has smaller pixels.

Note that this is different from changing the sharpness of the photo itself. When you adjust the sharpness of an image in an image editor like Photoshop, you're changing the image itself and not just the way it's displayed. I don't think this is what you're asking about, though.

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  • \$\begingroup\$ Well it kind of is. I know changing the size doesn't change the image itself. I have a d3100 and feel that it cant give me the sharpness and depth of field i want. So i was hoping shrinking the image would create the illusion of increased sharpness. \$\endgroup\$
    – Cody Pace
    Commented Apr 5, 2016 at 2:35
  • \$\begingroup\$ @CodyPace The 14.1 megapixel sensor in your D3100 should be fine for printing sharp photos at, say, 8"x10". If you're going for maximum depth of field you may be trying to shoot at very smaller apertures, like f/22, and diffraction may be limiting sharpness. Try some shots at f/8 and see if you can get acceptably sharp photos in the area of focus. If no, the lens may be the problem. \$\endgroup\$
    – Caleb
    Commented Apr 5, 2016 at 2:59
  • \$\begingroup\$ Ok i'll try that. I'm trying to take pictures of cardinals. Specifically one that shows one eating and is sharp enough to show the details of say the worm it's eating. I have 55-200mm nikor lense. I tried full zoom with 5.6 apeture, 1/1000 shutter speed, and auto iso, but the detail still isnt fine enough \$\endgroup\$
    – Cody Pace
    Commented Apr 5, 2016 at 3:33
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    \$\begingroup\$ @CodyPace Sounds like you actually have the opposite problem. AFAIK, Nikon's 55-200mm lenses are both f/4-5.6, meaning that your lens is wide open at f/5.6 and 200mm. Most lenses are a little soft at their widest aperture, and you also have the least depth of field there. Shooting at a smaller aperture like f/8 will give you a sharper image, and 1/500s shutter speed will still be plenty fast enough. The smaller aperture will also give you more depth of field, so a higher likelihood of the subject being fully in focus. \$\endgroup\$
    – Caleb
    Commented Apr 5, 2016 at 3:54
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    \$\begingroup\$ Ok i'll try that next time. After reading this comment i saw an article talking about the "sweet spot" of a lens. So maybe backing off to about 180mm will help as well \$\endgroup\$
    – Cody Pace
    Commented Apr 5, 2016 at 12:13
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No the opposite is the case, the higher the true resolution* the more details you've see, and the more details the more sharp the images appears.

Although sharpness is limited by the display's resolution, downscaling will still make the images appears sharper when it's higher resolution.

*true resolution is not just the resolution of the image, but the actually perceived resolution or level of detail and contrast.

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The term sharpness is directly related to contrast - a detail (colour transition) being sharp means that the brightness ratio between adjacent regions is high. This one is not sharp enter image description here because the brightness changes smoothly across the image. This one is sharp thoughenter image description here.

Another pair of examples. This is sharpenter image description here. And this, the version scaled down by 66% in the mode "bicubic sharper"enter image description here, is not.

It is a simple demonstration that an arbitrary image may only become sharper if recorded at higher resolution and may only get worse if scaled down. These images are demonstrating worst case and your photos will never look as bad downscaled because they do not contain the high contrast ortogonal details.

Now regarding your actual use case.

The only thing I haven't seen discussed is photo size. I know that when you zoom in on a photo, it becomes pixelated quickly.

It looks like you are viewing the photos on a screen with limited resolution. It means that you are always viewing the image scaled down and limiting the sharpness (as demonstrated), and a photo will never be as sharp downscaled as it is originally.

Now, the question is in the method of scaling which the viewing program applies. A program is forced to downscale the image and may do so differently: quickly and dirtily or a bit slower and make it look good. To make it look good (i.e. sharp) the program should apply some sharpening.

However, it does not make sense to do so because it may impose false impression on the photographer about photos being sharper than they are. Photo editing programs are not for exposing the result, they are made for managing the intermediate material.

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  • \$\begingroup\$ Ok this explains alot. I was thinking about it all wrong. So basically when a photo shrinks it is effectively losing pixels unless the display its viewed on has higher resolution. I think i got it. Thanks for all the help everbody! \$\endgroup\$
    – Cody Pace
    Commented Apr 5, 2016 at 12:16
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Whatever, stick to viewing on 100%. Plus take that extra measure of saving for the web if that's where the image is destined.

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  • \$\begingroup\$ If shooting RAW plus JPEG, bump up the LR clarity to 40 to bring the contrast up to match the JPEG. I find RAW is best processed in the manufacturers software as deals with high ISO better plus retains the overlay for focus points. \$\endgroup\$
    – Michael Tuner
    Commented Apr 6, 2016 at 12:17

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