Friday, 31 July 2009

'How Do You Do It?'

Some weeks ago, I was asked "How do you do it?" on this thread on the Pentax User forum. The enquiry arose after I posted a particular photo, and was later clarified as "I've got the same equipment as you, but things never come out as sharp as yours", or words to that effect.

This raises a couple of issues, and steers me away from the obvious answer of 'it' being all credited to my amazing artistic ability...

Sharpness in digital images is, as far as I'm concerned, down to three things:

1) Equipment - Unless you've got a camera and lens capable of producing a sharp image, you're going to struggle to produce sharp shots of any decent size. But the key phrase there is 'decent size'. A soft or blurred photo can appear sharp when reproduced at a low resolution, either as a small print or on the web.

Image appears sharp at this resolution, but is actually blurred

The photo above is blurred through camera shake (shutter speed was 2/3 second), yet at this size it looks sharp. I would be very reluctant to print it at anything larger than 6" x 4".


2) Technique - As long as you hold your camera steady enough, and ensure your shutter speed is fast enough to freeze any subject movement, and you focus correctly with sufficient depth of field, then you'll get as sharp a shot as your equipment is capable of.

If your shots aren't sharp, take a moment to first assess whether something about your technique is lacking, before you blame the lens or camera. Blurred image? What sort of blur? If everything has a smeary look to it, then it's probably camera shake. Put your camera on a tripod, or increase your shutter speed. If the smeary blurring only affects your subject, then the shutter speed was too slow to stop motion blur caused by the subject moving, even though the camera was steady. Is something in focus, but the subject not? Then the focus is wrong. Is too little of the subject in focus? Increase your depth of field by reducing your aperture (change from f/4 to f/11 for instance).

By knowing how different sorts of failing in technique show themselves, you have a chance to correct them.


3) Processing - The way that a digital photo is processed for showing on the web or as a print can have a massive effect on its apparent sharpness. Consider the following two images, and ask yourself "which photo is sharpest?"

Bracken shoot, first in a sharpness comparison

Bracken shoot, second in a sharpness comparison

Well, that was a bit of a trick question, as they're the same photo, just processed differently. Therefore the actual photo is obviously as sharp as it is, but the images presented here are quite clearly 'soft' and 'sharp'.

The first was resized from the original in one go, using the Photoshop 'Resize' option (Bicubic algorithm, as always for me), with no sharpening applied at any stage, then 'saved for web' with a medium compression setting (High - 60%).

The second was sharpened using Unsharp Mask whilst still the original size (2592 x 3872 px), with settings of Amount: 150%, Radius: 0.8px, Threshold: 0 levels. It's how I treat most of my originals as a 'capture sharpen'. I then halved the dimensions of the image (1296 x 1936 px) and applied USM again, but with a percentage of 75%, then resized again (500 x 747 px) and applied USM again, at 70%. This final sharpening is done by eye to ensure it's not overboard. Save for Web was again used, with a higher quality setting (Very High - 80%).

What these two images show us above anything, is that you can't compare your photos to anything you see on the web, without first knowing how that image was processed in order to get it there. I know my bracken shot is sharp, but if the only representation of it that anyone ever saw was that first one above, I'd be the only one thinking that.

Just in case this still leaves the question "How do you do it?" unanswered, I'll be posting again soon to explain exactly how that bracken shot came about.

It's a simple image, but there were various stages involved to get me to it - like everything in photography it was a journey, taking me from one idea to the next, one composition to another. Some worked, some didn't, but it was a gradual, refining process, until the feelings I had and the sights before me, were distilled into this final photograph.

It's something I cover in my workshops, but for those of you that haven't yet been on one, keep your eyes peeled...

4 comments:

Anonymous said...

Hi Dan
I came here following your comment on the thread although I often do visit your blog :).

And let me tell you, this is absolutely enlightening. What you just explained has opened avenues for major improvements in my post processing skills :).
Thank you again for such a fantastic insight into the world of post processing.

I will be keeping an eye for anything else you put on :). You got an avid follower here :)
Regards

Amin

Tim Houghton said...

Hi Dan,

You're comparing an image with no sharpening at all, and one which is sharpened 3 times.

Do you have any examples of an image which has only been sharpened one time? Perhaps one sharpening right at the end after all the resizing? Is there much difference to the 3x sharpened one?

Thanks!

Tim

Dan said...

Hi Tim,

At this size of image, there's no a huge amount of difference between an image sharpened once at the end, and one done in three steps as shown. There is a slight difference, with more detail visible in the three step one.

I often use a free program called 'EzThumbs' to resize images for posting on the web, so I'm obvioulsy not that fussy with the amount of control I have, just as long as they look good enough. ;-) EzThumbs does a pretty good job though, and can batch process, resizing, sharpening and renaming at the same time.

However, the point of that part of the post was mainly to convey that the same photo can appear very different, depending on the post-processing applied.

All the best,
Dan

Tim Houghton said...

Thanks Dan, I will have to give it a try. Only on more important images though, I'm too lazy to do this for every one ... I also use a drag-n-drop image resizer :)