Big picture considerations – lenses and software comparisons

I recently sold a couple of large prints to a friend and went through a couple of days of testing how to get the best appearance from big enlargements.  Along with that I’ve been reading about sharpness differences in lenses and wondering about the impact on enlargements.  Being a nut for sharpness in my landscapes I decided to do a little testing on my gear and see what differences I could find along with techniques to maximize sharpness.

You may never need to worry about this issue but I’m the photographer who walks up and puts my nose right at a big photograph just to see how sharp it is.  For normal people, the “correct” viewing distance is around 2 times the diagonal dimension of the picture (where infinite sharpness is less of an issue).  Your brain is pretty good at dealing with this – watch people at an exhibition moving back and forth in front of a painting or large photo and  you’ll discover most of them land in the same spot, which is around 2 times the diagonal of the image they are examining.  Has to do with angle of view of our eyes and how much we jump around in an image to take it all in.

Anyway, to compare lens sharpness I have two lenses with a 50mm focal length – one is a fixed macro at 50mm and the other is a zoom whose range includes 50mm.  In order to learn what differences might show up in processing I have two software tools for enlarging – Photoshop CS5 (bicubic) and Perfect Resize 7 (formerly known as Genuine Fractals).  Software packages make enlargements by literally creating new pixels in your image using sophisticated algorithms that try to made the new pixels blend in with the old ones.  I can’t begin to explain how this works – it’s just magic to me.

My test is a simple one:  photograph a straight edge with the two lenses at a fixed distance and then enlarge the image with the two software tools and compare the results.

As a summary I found the two lenses have little difference in sharpness in this test – the differences were greater between the software tools than the lenses.

I set up my camera at 64 inches from my target (just a random choice), a razor blade in front of a piece of white foamboard.  Lighting was from above, a 65 watt flood light (hence the really warm color in the images).  Camera was on a tripod, manual focus using LiveView on the back of the camera and a 5 second delay between the mirror lock-up and the shutter release.

I took the two image files (one for each lens) and processed each through the software tools, enlarging the image to 30″ in the longest dimension, which is about 2.5 times larger than the original image at 300 dpi.  After setting my view in Photoshop to 100% I cropped each image to the same dimensions.  No further processing was performed and the final, cropped images were saved as JPEG’s at maximum quality.

What I’m seeing is little difference between the lenses for sharpness; i.e., rendering the edge of the razor blade as a crisp, distinct line.  Viewing the original files at 200% showed little difference.  As far as enlargement, though, there are definite differences between the software tools.

Photoshop’s bicubic enlarger results in a smoother look to the final image, which for me results in a less sharp edge.  Perfect Resize did a better job of retaining the sharp edge but the work of the algorithm to add extra pixels around each existing pixel gives a type of pointillist look to the image (granted, when viewed at 100%) that Photoshop’s smoother result doesn’t have.  I’m concerned the image from Perfect Resize will be more sensitive to halos during final sharpening than Photoshop’s version, these halos being what makes some digital images look artificial to the eye.  In final sharpening the software doesn’t know which pixels are original and which were created during the enlargement so it works on all of them, which can result in artifacts around edges that distract from the image.

Two conclusions.  First, using what I already know about maximizing sharpness in the camera minimizes differences between the two lenses I use – tripod, manual focus, mirror lockup, shutter release delay.  Second, at significant enlargements (greater than twice original size) I need to be careful with the software tools, perhaps choosing one over the other depending on how important fine details are to the final image.  Additionally, subsequent sharpening will have to be applied carefully so as not to hurt all the prior work getting to a pleasing, larger image.

From all this I’m less terrified about offering larger prints on my website as I now know what to watch out for as I make adjustments to the images I upload to my site.  It would be nice if one tool did everything perfectly but photography, like other crafts, has learned more specific tools applied correctly usually return the best results.  That and the craftsman knowing how to use them properly and for the right application.


Old dogs, new tricks

While in photo school one of our instructors kept returning to the same subject again and again – focusing on the back of the camera.  At first I thought he was talking about using the LCD screen instead of the viewfinder, but eventually I realized he was using a button other than the shutter release to activate the auto focus.  He went on and on about the virtues of using this method especially where focusing on one part of the composition and using another part for the exposure reading.  Several of my classmates switched to the method and a few seemed to like it better but I never found a body of reason to make the switch.  Maybe I’d found a way to use the shutter release to achieve what he was getting with two buttons.  Besides, after switching my camera over to that method I kept getting confused by forgetting how to focus.

Well, I finally got advice that convinces me to switch to this technique, but only for a specific application.  On my crane photo tour I kept getting really lousy images of flying birds; lousy in that they weren’t in focus.  I was using shutter speeds well over 1/2500 sec. and keeping the bird in the center of the viewfinder with smooth tracking but all the images kept looking soft or even fuzzy.  When I mentioned my frustration to one of our instructors, Dave Showalter, he asked some questions about my settings and then shared how he overcame a similar frustration.

What I learned from him almost instantly improved my flying bird images, increasing the keeper images from less than 5% to well over 50%.  Oddly, it involves using that “focus on the back of the camera” trick I’d discarded from school.  Basically, it appears my problem was focusing on the bird with the shutter release (push half-way down to activate the auto-focus) in single-focus mode.  In this mode the camera focuses, then locks the focus, takes the exposure reading, then fires the shutter.  The very small lag between the auto-focus engaging and locking and the rest of the sequence occurring was resulting in the initial focus getting “off” as the cranes flew forward in that time span.  The changes were simple.

Olympus, as most DSLR’s, has a continuous focus mode where the camera keeps adjusting the focus right until the shutter fires.  That’s the first change of setting.  Second, I can set the continuous focus mode (and only the continuous focus mode) to use the Automatic Focus Lock (AFL) button on the back of the camera.  Third, in continuous focus mode I changed from a single focusing point in the camera (I usually rely on the center one) to the full matrix focusing where all the focus points are engaged and the camera picks out what should be in focus.  With a bird flying against a mostly empty sky the camera goes right to the bird for focus, and in continuous mode, keeps adjusting the focus right to the point of shutter release.  With focus and exposure separate, I get much better percentages of sharp subjects as they move, and the exposure only when I actually release the shutter.  Sure, I have to use two fingers instead of one but Olympus’ placement of the two is easy for me to become comfortable with and more practice can only improve my two-finger-picking style.

How did it work?  Take a look.

This has to be one of the sharpest flying crane photographs I’ve ever made so I’m definitely keeping this setting on my camera.

Alternative photo sharpening

One thing that is great and frustrating about Photoshop is the many ways to accomplish the same outcome.  Almost as if the original software designers mashed together different programs from different fields of work, making one big program but keeping all those unique pathways.  Even when you get a decent workflow there’s that lingering feeling in the back of your mind that somewhere, buried in the tools and menus, there’s a better way or a more effective means.

Sharpening is my photography quirk.  I want my landscapes and nature photos to show fine detail at all scales – down to the molecular level if possible!  So, I’m always looking for sharpening methods that give me better results, even when the workflow is a little off the beaten path.

I ran across an article this week that uses a different color space as a sharpening tool.  Color spaces are constructs that determine what colors will be displayed from an image on your screen, an inkjet print, a press print, etc.  The typical space used in Photoshop is AdobeRGB and it does a good job of presenting an accurate rendition of what your eye saw in a scene.  The different color space in the article is called LAB and the unique aspect of it comes from how it handles color information.  The LAB space separates the light-to-dark information from the color information (unlike AdobeRGB) so you can sharpen just the black-and-white parts of an image without interfering with the color part.

After playing around with the technique described in the article I’m pretty pleased with the results.  To the usual Photoshop workflow it doesn’t really add many extra steps.  You just have to remember to convert back to AdobeRGB in order to print or display on the web.

Here’s the article:

And here’s an image I used the technique on – check out the detail in the feathers on her back:

Workflow discovery of the week – B&W to sharpen color

Making an image appear sharper involves increasing the contrast between the dark and light areas in the small details of the image.  This doesn’t bring an image into focus more than you’ve already got (that’s a function of your lens and focusing, either auto or manual) but it can be a way to improve the appearance of an image, to make the details stand out to the viewer.  There are several ways to increase sharpness, including automatic tools in photo editing software, but I’m interested in controlling sharpness or giving a slightly different look to my sharpening.

Here’s a method I’m working with right now.  In Photoshop, create a B&W adjustment layer above the background layer.  You can make adjustments to the different tones in the B&W image but I let mine use the default settings.  Then make changes to the blending mode for the B&W layer until the details pop out.  I’m using Hard Light and then adjusting the opacity to 50-60%.    Here are the before and after versions:

Original image

Adjusted image

As with most tools, this probably works differently on different images so your mileage will vary as you play with this method.  One advantage of this method is the ability to brush on the adjustment layer mask to hide the effect on the image so you get sharpening in just the areas  you want.

Landscapes, either the grand ones or the details, are usually expected to be sharp as the viewer wants to see in a photograph the same elements they would see if they were standing where your camera was placed.  For best results, put your camera on a tripod and use a remote shutter release, but afterwards don’t be afraid to work on the sharpness of your images to get the desired effect.  The method here is just one more item in your toolbox for creating wonderful photographs.