Working on Backgrounds

M is for Mantis
Originally uploaded by Dalantech.

Still experimenting with different materials and techniques. First up is a mantis that I shot in front of a piece of light blue construction paper. II though that since the paper had a matte finish it would make a good background, but oddly enough it looked kind of grey in some of the images that I took. Also notice that the pseudo pupil is almost missing in the critter's left eye -that effect is caused by the way the flash reflects off of the compound eyes (a mantis doesn't really have a pupil). The second flash that I was using to illuminate the background all but washed it out, and what's left is in the wrong position. In the future if I use a second flash when shooting a mantis I'll place it directly behind it.

For this next shot I used a vinyl table cloth, and shooting against a reflective surface works a lot better than shooting against one that has a texture.



There's no natural light in those first two shots, but this next one is a mix of natural light and flash. I set the shutter to 1/20 of a second to expose the reeds in the background, and then let E-TTL metering expose the subject with the flash. This is my preferred method for keeping the background from being black, especially when I can get a good mix of natural light and flash. Even though the sunlight was pretty harsh (taken at about 3PM on a cloudless day) the color and saturation in the background look good because it's out of focus and a little under exposed. A digital sensor reacts to under exposure in the same way as color positive slide film -colors saturate. The downside to this method is that there can be enough natural light to partially expose the subject which makes freezing motion difficult.



I've also noticed that when creating artificial backgrounds that smooth backgrounds do not look as good as ones that have some color or texture variation (especially if the background is not blue). The brain sort of expects vegetation to keep the background from looking smooth. Compare the dragonfly in the previous image with the bee in the next shot -this one is all flash:

Macro, the 1/f Rule, and Flash Durations

Many, many, moons ago Fred Vachss made a really interesting post over at DP Review concerning the 1/f rule and flash durations as they pertained to macro photography. Basically we were all wondering what shutter speed (or flash duration) was necessary for freezing motion at different magnifications. The mistake that a lot of people made back then was jumping all over the lowest flash duration (flash at minimum power) and claiming that the flash could freeze anything. Unfortunately you'll almost never be shooting with a flash at minimum power, so you'll rarely see those lightning fast bursts of light. The only time I've been able to expose a brightly colored subject at life size magnification and 1/64th power with the MT-24EX is when the flash heads are bare. Not exactly the best light quality... ;)

 If you boil Fred's post down here's the 1/f rule for macro photography: Shutter speed = 1/f((1+m)2) where f = focal length of the lens and m = the magnification you're shooting at. So at life size magnification you need a shutter speed that's four times faster than using the same focal length lens for a non macro photo, at twice life size your shutter needs to be six times faster, etc. Substitute flash duration for shutter speed if you're using a flash as the primary, or only, light source. Also keep in mind that the 1/f rule, even modified for macro photography, is a minimum requirement. To "be safe" you'd never want to get close to 1/f rule speeds. Now let's add insult to injury and explain why: Noticeable diffraction is defined as light rays spreading out so that they strike half way into adjacent pixels. The 1/f rule assumes that you're trying to keep the motion in the scene to less than one pixel, and not to less than one half of a pixel. So how easy is it to amplify diffraction with very small amounts of motion, less than the width of half a pixel, while the flash is firing? It's always been my contention that diffraction isn't the monster that most people have made it out to be, and that there is a very synergistic effect between motion and diffraction. You won't necessarily see motion blur in your images but if you're not doing everything you can to minimize movement, and to keep your flash durations as short as possible, you'll have difficulty getting a lot of detail when you shoot at high magnification and high Fstops.

One of these days, just for the focus stacking crowd, I'm going to make a post about how your photos may be diffraction limited even if you're shooting with a lens that's wide open. It has to do with the diffraction limit of green light being four micro meters at F2.8, at the center of a digital sensor (as you move away from the center of the sensor diffraction gets worse). So if your camera has pixels that are four micro meters wide (like the 50D, 60D, and 70D), or smaller (like most of the Power Shot models), you're already recording diffraction at F2.8...

 P.S. Not that I have anything against focus stacking -it's just another tool in your tool bag, and some day I might actually stack an image or two. But I do think that a lot of the people who stack their images are actually doing more to defeat macro motion blur than diffraction...

Reminders

Hangin' Out
Originally uploaded by Dalantech.

I'm dialing up the way back machine for this image (I took it back in May of 2007). It's a reminder for me of three things: How far I've progressed as a photographer since I took this frame, the need to back off and show my subjects in their surroundings more, and to look around for opportunities to take a shot that I really didn't intend to take. I was chasing a butterfly and not having any luck at all when I turned to my right and saw this beetle that seemed to be watching me chase the butterfly. Could have sworn I heard him laughing... ;)

The Universe Says "No!".

Dragonfly Rescue
Originally uploaded by Dalantech.

While I was out at the lake testing a new diffuser I noticed that there was something odd going on with the light. At first I blamed the diffuser, but then I realized that my MT-24EX was firing at almost full power, even though I was only shooting around 3x at ISO 100 and F11. Later on that evening I realized what was going on while taking some test images at my kitchen table -the "B" flash head was only firing intermittently.

That's two hardware failures in as many weeks -bummer.

I guess if the gear is going to fail I'd rather it happen now then early next spring. Canon has already given me a repair estimate on my MPE-65mm (about 200 USD) and I sent the MT-24EX to the service center in New Jersey this morning. With any luck I'll have all my toys back in about two weeks. Until then I'm going to explore using a standard camera flash on a bracket.

Sometimes the universe says no... ;)

Oops I Did it Again

Weevil at 5x
Originally uploaded by Dalantech.

Not long after I photographed the Weevil to the right my MPE-65mm macro lens started giving me the dreaded "Error 01" message.

Oops...

The least time it happened it set me back about $300 for parts and labor. I'll be sending the MPE back to New Jersey for repairs today. For now it's back to the EF-S 60mm and tubes.

What are You Trying to Accomplish?

Dinner for Two
Originally uploaded by Dalantech.

I was reading a piece over at Strobist and one of the questions in it is the title of this post. For me the answer isn’t all that simple. Early on I knew that I didn’t want to paint myself into a corner by using a lot of gear. Tripods and focusing rails are slow, and really limit what you can and can’t photograph. I had actually given up on using tripods back when I use to shoot landscapes, because I realized that all a tripod was really doing was forcing me to slow down and evaluate a scene before I set it up –cause there’s just no sense in taking the time to put the camera on one if there isn’t a decent shot to take. So I simply got into the habit of pausing for a moment, evaluate the scene and my surroundings, and then decide if I’m there’s a photo to take and how I’m going to take it. I do the same thing today, often passing on opportunities to take images that I know I won’t keep.

It’s a little tough to chase a honeybee with a tripod...

Keeping the gear to a minimum allows the subject to dictate how I’m going to photograph it, instead of using a lot of equipment and restricting myself to only those subjects that conform to my gear. It can also be said that any serious discussion on hardware is kinda pointless, since my choice in camera equipment might be completely alien to you and counterproductive to your way of shooting. So there’s no right or wrong here, just differences in style.

The other thing I want to do with my photography is to change your perspective of the small world. I want you to see insects as more than “just bugs”. Shooting at their eye level allows you to connect with them, to see some personality. Whether or not you believe insects have a personality isn’t important, but my being able to project the impression of a personality in the way that I photograph them is.



So, what are you trying to accomplish?

High Magnification, High Fstop, and High Detail

Carpenter Bee at 5x
Originally uploaded by Dalantech.

Note: If you firmly believe that you have to use a tripod, or focus stack, or both to get a lot of detail at high magnification and Fstops then stop reading this post right now –I’ve got nothing for you.

When I first got into macro back in 2006 there were two prevailing themes: You had to use a tripod to get sharp images, and diffraction is the primary reason why you can't stop a lens down and get those sharp images. But something really odd was happening over at the Fred Miranda Macro Forum: Occasionally someone would post a really sharp image taken at high magnification and high Fstop that wasn’t focus stacked. I remember there being more than one person doing it and they wouldn’t explain how; either they wanted to keep the technique to themselves, or they were afraid of going up against overzealous focus stackers who believed that the only good macro images were those that are razor sharp at 100% pixels (unfortunately even today some still equate sharpness with quality). I was curious to know how they were pulling off such highly detailed images at high Fstops, and I finally figured out part of the puzzle sometime around 2008, but the last piece didn’t come together until several years later.

I wanted to let the subject dictate how I shot it, and to go after moving targets, so I came up with the Left Hand Brace Technique for taking control of the motion in a scene so I could get the compositions that I was looking for without using a tripod (and without cropping in post). I started to realize that the more control I had over the motion in the scene the sharper my images were (the first piece of the puzzle) not because some of them were suffering from noticeable motion blur but because slight motion, as little as the width of half a pixel, can amplify diffraction. I started to think of the phenomenon as “macro motion blur”. To explain how motion blur can mimic diffraction you first have to really understand what diffraction is.

The classic definition of diffraction is light bending as it passes through a small opening, and that's true. But there's a little more to it than that: The rays of light actually expand, like a cone, so that light rays that should hit a single pixel are now bleeding over into adjacent pixels. When that bleeding over reaches half way into those adjacent pixels you'll see a loss in image quality -diffraction has taken your lunch money.

But if you can wrap your head around expanding light rays causing a loss of detail then couldn't slight motion, as little as half a pixel of movement during the exposure, amplify diffraction? My experience has taught me that it can.

Right about now some of you are thinking "But wait a minute Mr. Macro Motion Blur, why do my images get sharper when I decrease my Fstop?!" To answer that question we have to first determine what your actual shutter speed is.

At macro magnification, high Fstops, and low ISOs, the light that your flash is producing is the only significant light source in a scene. To prove it just set your camera to manual mode, F11, 1/200 of a second (or whatever your maximum flash sync speed is for your camera), ISO 100, and go out and take a photo on a bright sunny day with your macro lens set to its minimum focusing distance (life size magnification). You'll have to shoot something really bright or reflective to get anything to show up in the resulting image. Then turn on your flash and take the same shot -there will be a major difference in what you can see in the photo. At higher magnifications, if the flash doesn't fire, you'll just get a completely black image. So your flash duration is really your shutter speed, since it's the major, or only, light source -the actual speed of the shutter doesn't matter...

So you set your camera to manual mode, F11, 1/200, and ISO 100. You've got a rig that will let you shoot at 3x, you take a shot hand held, and the resulting photo isn't very sharp. You then set your camera to F8, take the same shot, and this time the image is a lot sharper. See, no more diffraction! Well there's only one little problem -when you went from F11 to F8 you opened up the aperture in your lens to let about twice as much light into the camera. Through The Lens (TTL) metering compensated for the increase in aperture (decreasing Fstop) by turning the flash on for about half as long -so your shutter speed (the flash) nearly doubled. Did you defeat diffraction or macro motion blur?...

For me the answer is simple, since I can get sharp images at up to three times life size at F13, and four to five times life size at F11 with Canon's MPE-65mm macro lens. The key is to get the flash as close to the subject as possible (to keep the flash duration as short as possible), use a diffuser that really diffuses the light (not one that just blocks the light), and look for ways to take control of the motion in the scene.

Diffraction does exist, but it's not the monster that most macro photographers make it out to be.

The second piece of the puzzle is to use a well diffused light source. If your flash produces really strong specular highlights you’ll end up with high “micro contrast” (a term coined by SteB). Those little bright areas will make an image look sharper than it really is, and you might think at first that high micro contrast is a good thing. But those same bright areas will limit how much sharpening you can apply during post processing. So what you really want are “soft” specular highlights where you can actually see texture and possibly even a little color behind them. The softer the light the more sharpening you can apply during post without making your images look over sharpened. Getting your flash as close as possible to the subject won't just help you to keep your flash duration short, it will also make your light look more diffused.

Since you're getting the flash close to the subject you don't need a long focal length lens -you don't need more working distance if the flash is close to the subject anyway, and short focal length lenses will give you more magnification when you start shooting with extension tubes. There's no such thing as a "bug lens" -all you have to do is learn a little about the habits and quirks of the subjects you want to photograph.

With this post I’ve pretty much given you the keys to the candy store…

Footnote: When I first published the Left Hand Brace Technique I got several hate emails and angry private messages on a few forums. It seems that quite a few macro photographers had been using the technique, but were keeping it quiet, and were really pissed off at me for writing about it.

Last but not least: I do lose some texture detail to diffraction –I can’t cheat physics. But there is so much depth and detail in my photos that people frequently ask me if I focus stack. I do not focus stack, and although there is nothing wrong with the technique (it’s just one tool of many) I’ve pretty much proven that it’s not necessary...