Robert Watcher
Well-known member
I have recently received about half a dozen emails and a couple of PM's from photographers asking my opinion on how sharp a lens is, whether one is better than another, or letting me know that they are having a hard time getting sharp images from specific lenses and asking for suggestions. . .
. . . so I thought I would post a summary of my responses here. I know it probably will not be popular because it is too simple and not very technical - - - just what I have found from a practical standpoint:
In my experience, much of the time acceptable sharpness has more to do with technique than it does the lens used. Some cameras do have a tendency to focus in behind slightly even when it appears that the focus point is on the right spot - this again is technique though and learning how to adjust for the camera so that it focuses more accurately.
If the focus point is right on a large subject and the image appears soft, then the culprit so often is camera movement - - - again a result of technique. To be frank, many of images that I have seen where the person who took the pictures thought they were out of focus, were indeed a slight double image resulting in camera blur.
All lenses are sharper when stopped down 1 to 2 stops (a normal sharp range would f5.6 1/2, f8, f8 1/2). Expensive fast lenses are sharper than cheaper zooms when shooting wide open - however most all lenses are comparable when shooting at the mid range of f stops.
Another factor is what photographers expectation of what sharpness is. My expectation is that the negative or file prints well and so I am not overly concerned with a magnified image and pixel peeping. I find that my sharpness requirements are fairly low compared to what many comment about on forums. If however your expectations are not overly high and you are not satisfied, then it probably is technique that you will have to work on - picking appropriate shutter speeds, taking time to focus accurately.
Another point worth mentioning is that all digital images are soft out of the camera (unless you are applying heavy sharpening in-camera) and I apply sharpening in Photoshop to every image that is printed and every image that is posted on the web. Particularly with web images, the downsizing of the file creates an even softer look that needs to be sharpened. For critial web images I even resize and sharpen at intervals of 1/2 size until I am am at the desired pixel size. The amounts of sharpening applied, need to be worked out through trial and error using starting points provided by different books or articles that can be found with a web search - - - and they are totally different not only for each application, but also for each different print size and the content of the image being printed. Sharpening is a learned art and there is not a canned answer to what is the best way to sharpen.
At any rate - most modern lenses do a great job for most normal applications. For portraits and weddings, I don't want the sharpest lens and so soften many images (using more edge sharpening for some detail and contrast). If I were shooting critical architectural images or other content where crisp sharp detail needs to be displayed - particularly at larger sizes - - - then I would not be using any of the DSLR cameras that are popular an would instead opt for at the least full frame digital cameras or more normally expensive medium format digital cameras - - - or probably shoot with 4x5 to 8x10 film and have it scanned. With film cameras and the best of lenses, I could not get an acceptable top quality architectural image at 11x14 and so I don't expect it from my digital cameras - - -although I have been surprised at times to have a digital file that does quite admirably at even larger sizes. And I have taken portrait images from digital files from 6 to 10MP cameras up to 24x36 for professional results. As always, it depends on the technique, content, end use, and expectations.
. . . so I thought I would post a summary of my responses here. I know it probably will not be popular because it is too simple and not very technical - - - just what I have found from a practical standpoint:
In my experience, much of the time acceptable sharpness has more to do with technique than it does the lens used. Some cameras do have a tendency to focus in behind slightly even when it appears that the focus point is on the right spot - this again is technique though and learning how to adjust for the camera so that it focuses more accurately.
If the focus point is right on a large subject and the image appears soft, then the culprit so often is camera movement - - - again a result of technique. To be frank, many of images that I have seen where the person who took the pictures thought they were out of focus, were indeed a slight double image resulting in camera blur.
All lenses are sharper when stopped down 1 to 2 stops (a normal sharp range would f5.6 1/2, f8, f8 1/2). Expensive fast lenses are sharper than cheaper zooms when shooting wide open - however most all lenses are comparable when shooting at the mid range of f stops.
Another factor is what photographers expectation of what sharpness is. My expectation is that the negative or file prints well and so I am not overly concerned with a magnified image and pixel peeping. I find that my sharpness requirements are fairly low compared to what many comment about on forums. If however your expectations are not overly high and you are not satisfied, then it probably is technique that you will have to work on - picking appropriate shutter speeds, taking time to focus accurately.
Another point worth mentioning is that all digital images are soft out of the camera (unless you are applying heavy sharpening in-camera) and I apply sharpening in Photoshop to every image that is printed and every image that is posted on the web. Particularly with web images, the downsizing of the file creates an even softer look that needs to be sharpened. For critial web images I even resize and sharpen at intervals of 1/2 size until I am am at the desired pixel size. The amounts of sharpening applied, need to be worked out through trial and error using starting points provided by different books or articles that can be found with a web search - - - and they are totally different not only for each application, but also for each different print size and the content of the image being printed. Sharpening is a learned art and there is not a canned answer to what is the best way to sharpen.
At any rate - most modern lenses do a great job for most normal applications. For portraits and weddings, I don't want the sharpest lens and so soften many images (using more edge sharpening for some detail and contrast). If I were shooting critical architectural images or other content where crisp sharp detail needs to be displayed - particularly at larger sizes - - - then I would not be using any of the DSLR cameras that are popular an would instead opt for at the least full frame digital cameras or more normally expensive medium format digital cameras - - - or probably shoot with 4x5 to 8x10 film and have it scanned. With film cameras and the best of lenses, I could not get an acceptable top quality architectural image at 11x14 and so I don't expect it from my digital cameras - - -although I have been surprised at times to have a digital file that does quite admirably at even larger sizes. And I have taken portrait images from digital files from 6 to 10MP cameras up to 24x36 for professional results. As always, it depends on the technique, content, end use, and expectations.
