How do you judge image sharpness

[gary payne]

We all strive to capture "sharp" images. The question here is, how do you define sharpness, and how do you judge

which images are sharp, and which are not?

 

I was reviewing images from a recent shoot using NIKON ViewNX to determine which images were "sharp" and which

were softfocused, subject to camera movement, or had any of the other problems we all experience from time to

time. I examine each image as it fills the screen, then at 50% increase, 100%, 200% and 400%. Even the sharpest

image I have suffers at 400% on the computer monitor. And, we know that the best image gives way at some point of

magnification.

 

So, I began to wonder, how to others judge image sharpness? I remember the film days when we had our light

boxes and lupes, and squinted at negatives and slides trying to judge which would produce good prints and which

would project well.

 

How do you make that determination today when your computer monitor is your light box?

[patricklavoie]

400% will never show you sharpness..but pixel.

 

look at your image at 25% 50% or 100% max. If you can see precise details, its sharp. if you cant see or barely see fine detail its soft. if you can see a halo around your image and it look like out of this world..its over sharp : )

 

how do you judge when a soup is too salty?..if it taste too salty!..well apply the same principle to sharpnes ; P

[sattler123]

Never judge a picture at more than 100%. Beyond 100% all you see is pixelation.

[geoffs1]

I shoot exclusively raw, and after a bit of experience I've gotten used to what an image that will look sharp after processing looks like displayed at 100% in Faststone Image-Viewer (my culling tool).

[alan_ginman]

How do you view your finished pictures? On screen? A4 prints? View them in that medium and judge that way. If you never print above A4 then any 'extra' sharpness is irrelevant.

 

Cheers

 

Alan

[kari v]

For 8x10 / 8x12 print 50% view is enough. Web? This is easiest, resize and have a look, no need to think about other media or viewing distance. HD TV is also very forgiving.

 

You'll get used to different % viewing and what that means to your prints but basically use your eyes, sharp is sharp. Computer screen and 100% view is very unforgiving lightbox, it's a bit like doing 20x24 proofs to make sure your 8x10 will be sharp. ;) (Actually only slightly joking here.)

 

At 400% your viewing distance should be something like... I don't know, how big is your room?

[matt_needham]

I make prints and look at them hanging on a wall. I don't care what photos look like at various magnifications. I only care what they look like when finished.

[KenPapai]

What Kari and Matt said. And, get yourself a few books on Photoshop Gary, assuming you edit via PS.

 

Sharpening for Print and sharpening for email/Web viewing are two entirely different animals.

[charlesheckel]

Correct answer: subjectively, so Matt Needham probably has it right. Sharpness is a perceptual phenomenon, in contrast with physical parameters such as modulation transfer function, image detail, resolution, acutance, local contrast, and so on and so forth, and so many factors work together to produce it that we're probably better off considering our output in context and coming up with an expression that works in that context.

[the photo messinger]

well...if you're going to be making a print, first make sure that your image resolution is at least 200 pixels/inch (but ideally 220 or higher). You also need to find out the resolution of the screen you are working on because it may be (and probably is) lower than the resolution of the image. If you are using Photoshop, you can go to Image --> Duplicate and name the copy something like "actual." Once "actual" is open, go to Image--> Image Size and change your resolution to the resolution of your screen and click okay. Bring that image up to 100%. If that looks sharp, then you are good to go.

[Tim_Lookingbill]

I sharpen for poster size enlargements checking for softening from uprez interpolation. This usually requires viewing the image

at around 400% to get a clean stairstep edge along detail because halos will become amplified a give an artificial appearance

when viewing the poster up close.

 

Below is a screen capture close up crop in CS2 with the original 6MP 3000x2000 @ 72ppi Pentax raw image on the left

sharpened to overcome interpolation uprezing a copy to 300 ppi at 30x20 inch poster size displayed on the right. This is how

sharpness will look printed at this extreme enlargement.<div></div>

[patricklavoie]

i think its best to know before how it will look on screen then printing for nothing?!

 

"..I don't care what photos look like at various magnification.."

 

Why then should you care about monitor calibration? since all you care its print anyway?

 

Because both could predict the print before doing it.

 

When i adjust my sharpen, i do it at 100%, then to judge if its OK on my inkjet i go to 50%, if its for commercial press, like amgazine, i go at 25%. If you find it too strong, not enough strong..well you adjust it.

 

Of course, depending on what type of paper you print would also be usefull for your final sharpen; a glossy paper require less sharpen vs a watercolor paper for example...