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The Need for Macro Flash

Flash the Key to it all:

If you read the page on Depth of Field or Shutter Speed you learned that unless it is a super bright day there is not enough light to hand hold your camera with a macro lens and get a good shot on a consistent basis. The way around this is to add light and since the bugs live in the wild the only choice is to add flash. When flash is added it can also be used in place of the shutter speed so its duration can be used to stop camera shake.

On the Home Page it said if you have lots of money it is easy, just purchase a dedicated macro flash from your camera manufacturer. They are great without question, if you can afford one go for it. However, they are expensive so not everyone can afford one and for the most part they are very limited when it comes to other uses. So, a real commitment needs to be made to go this route and it's not like an old lens where there are plenty of used ones where you can find a deal. When you do see used macro flashes they are most likely proprietary to an older model of camera or still very expensive.

So, what about these other ring light flashes like ones that you see on ebay, etc? Most of them are not real macro flashes. They are a bunch of LED lights in a ring (Ring Light or an LED flash that has a long duration). So, wow, great portable constant light - wrong! What they actually are is some light to assist you perhaps in focusing, or perhaps jump you up a stop (read the fine print) not enough for getting the flash duration needed to eliminate camera movement. There are a couple of exceptions in the 1-2 hundred dollar range, however the reviews on them say the quality of them is very poor so they don't last and are a waste.

If you have a flash already that may determine your choice as it is always good to utilize what you have (and it can be used). But if you don't and opt to go for a dedicated macro flash your options are limited as most manufacturer's only offer one or two and either would make a good choice. Keep this in mind, these things are kick butt great and worth every penny. The quality is there, they are durable, and the technology allows for consistent excellent shots on automatic.

Because of the expense of a dedicated macro flash people have come up with alternatives. I have seen numerous ones online and to save a buck or two I decided to give them a try. (see the next page Macro Flash Brackets) But first lets look at the options.

With flash there are really three choices, one being a dedicated automatic E-TTL unit, one where you can adjust the output manually and the other a manual unit with no adjustment. With automatic it is rather easy, set your camera on manual, your shutter speed to 1/200 (or whatever your manual says) and your aperture to f/11 and make a test shot  You should not be off by much and if you are you adjust your flash compensation not your camera in most cases. (depending upon your camera and ambient light).

With manual flash (ones where you cannot adjust the output) it will take a little practice, I would suggest starting with a 1/200th of a second and add a couple of small cheap softboxes and try  f/11(ISO 200). This is a starting point, what you will find is that with a little practice you will get to the point where you will be able to look at a shot, move up or down an f/stop (or adjust the ISO) and be real close to a great exposure. Keep in mind you are adding light so if it is a bright day you will be adding less than on a cloudy day. Keep in mind that you are also usually at or about at the same flash to subject distance on every shot.

Also, really look at the background, a small spider with a dark background is easy to get washed out. One thing about bugs is that some of them reflect light different than others. The key to all of it is practice. I cannot emphasize this enough, if you go out and take 20-30 shots review them, take a few more and review them and call it a day after a week or two of doing this you will get to the point where you will see a scene and dial in a setting and be within a half a stop. 

How flashes work - Flash Duration:

You would think that if you have a flash that is adjustable it would be brighter when the power is turned up. It does not work that way. What happens is that the flash stays on longer. So what you are really doing is changing the flash duration (the time the flash stays on - when you think about it is is just like shutter speed - on longer, more light gets to the sensor).  
Please note that when looking at flash durations there are different testing methods for what is considered "ON". On this page I am making some general assumptions such as at full power the flash will be at 1/1000th of a second. Canon actually states the 580 EX II is 1/833rd of a second on full power and they don't publish lesser power durations. With another testing method it is at 1/275th of a second - (depends upon what you consider on), All in all it doesn't really matter as the principle is the same. If I plug in 1/833rd of a second instead of 1/1000th, I still need to be at 1/8th power. Only instead of being at 1/8000th I may be at 1/6400th of a second.

Here is a really good webpage about different flash durations.

On most flashes full power is around 1/1000th of a second. Now if you think that a 1/1000th of a second will always stop camera shake you are wrong, just plain flat out wrong! and it is easy to prove because the magnification is so high when taking a true macro shot. However, it is a lot easier to stop camera movement with a 1/1000 of a second than it is at 125th of a second. 
 
When I thought of using flash I figured I would not have to worry about camera movement as the flash would be going off at an incredible speed. You know like when they stop a bullet in mid air going through an apple or capture an arrow going through balloons. That is not the case, you will be adding light to some existing light and the flash duration has to be short enough for the shutter curtain to open and close. Those stop action shots of a bullet were actually done with a very specialized flash (over 10K) in a completely dark room.

What I have found is that at 1/4 to 1/8 power I almost always eliminate all movement. (at 1/8 I always do at up to 1.4:1). The goal here is to take consistently good shots which means eliminate the obstacle if at all possible.  There has to be a little disclaimer here, this chart is below 1.4:1 magnification, with a higher magnification  you would need a shorter duration to stop movement.

 

Shots Ruined by Camera Movement Caused by Hand Holding

(from personal experience - yours will vary from this)

Flash Power Percentage of Failures
No Flash 99%
Full Power 25%
1/2 Power 15%
1/4 Power 5%
1/8 or Lower Power 0%

 

Now on a Canon 580 EX II this is a flash duration between 1/4000 and 1/8000th of a second. I am using a Canon 580 EX as an example as it is one of Canon's most powerful flashes.

If you are thinking well, if my flash will fill up an entire room and I am only taking a photograph 8-10 inches away from my subject it should not be much of an issue to use 1/8th power on a flash. That is really not the case as there is a thing called the "Bellows Factor". What this means is that there is a loss of light when you move the lens further from the film (sensor). What happens in a macro lens is that once it is in the macro mode you have exceeded its normal length (pushed the optics further away from the sensor) and you need to compensate for it. On a Canon camera it does not show this change when you look at your settings. It does on a Nikon as far as I know.

This bellows factor for a Canon 100mm lens is +2 at 1:1 magnification (you will find the factor to use at what magnification in the lens manual - something real men do not read). So, if we dial in f/16 we are really at f/32! This is just to get 1:1 magnification. If a little more magnification is desired by using extension tubes or a tele-converter it continues to increase. One of my favorites is to use a 1.4 tele-converter to get 1.4:1 magnification. When I add a stop for that I am at f/45.

Flash output is stated by what is known as a Guide Number (GN). With Canon it is easy as on their flashes the model number is the Guide Number in meters.  The way it is used is that GN is divided by the distance of the flash to the subject to get the aperture to use at ISO 100. Sort of simple really, with a GN of 80 at 10 feet you would be at f/8. Now if the flash has a GN of 160 at 10 feet we would be at f/16. If we shot at half power (160/2) we would be back at f/8.

Lets look at the powerful Canon 580 EX and see what can be used. It has a GN of 58 meters / 190 feet.

If we use the 100mm macro at 1:1 magnification we add 2 stops so at F/16 we are at f/32.

190 (GN in feet) / 32 (Aperture) = 5.93 feet - Great! it can be done as we are about 1 feet foot from the subject.

But that GN is at full power which is at 1/1000th (actually closer to 1/800th) of a second. We want to get to 1/8 power to stop all movement. To do this we divide the 190/8 to get the GN at 1/8th power.

190/8=23.75

23.75 / 32 = .74 feet

Convert feet to inches 12 * .74 = 8.9 inches. So at 1/8 power the flash has to be about nine inches from the subject. This is about the length of the lens itself. So the options are:

  • Increase the flash power this option is out as it increases the flash duration.
     

  • Increase the ISO This option will work for some as it is based upon the capabilities of your camera. However the best results are always from the lowest ISO, so this option should be saved until last.
     

  • Add an additional flash - This option looks good but there is a catch to it. In physics there is a thing called the Inverse-Square Law that applies to light. In a nut shell it says at twice the distance you need four times as much light. So this means that another flash will only give you one additional stop.
     

  • Move the flash nine inches away from the subject with a Flash Bracket. This is a very simple solution, to get to 1/8th power. Which really means put your flash head at the end of your lens. Keep this in mind. this is at 1:1 magnification.  If you recall from above the reason we needed so much light (2 Stops) was because of the Bellows Factor which changes as magnification changes so this is best case, if we want more magnification we will need more light.
     


The Inverse-Square Law that applies to light

In a nut shell the Inverse-Square Law says at twice the distance you need four times as much light. Just think of a flashlight at night at twice the distance it is a 1/4 as bright.

To calculate how much light you will have when you add an additional flash you take the Guide Number of the Flash and square it and do the same for the flash you are going to add (just incase they don't put out the same power) , add up the two new numbers and calculate the square root and you get the new Guide Number.

From above the Canon 580 has a Guide number of 58 so 58 squared would be 3364. (doing this in meters now)

So if we add 3364 and 3364 (for the additional 580 flash) we get 6728 we then calculate the square root of it and we get 82 as our new guide number with one added flash.

With a guide number of 58 at 10 meters we would have an f/stop of 5.8 (close to 5.6) with the extra
flash we are at 82 so we would be at f/8.2 (close to f/8) - one stop per flash!

If we add two flashes it becomes 3364 * 3 = 10092 squared provides a GN of 100 and finally with three additional flashes 3364 * 4 = 13456 squared gives us a guide number of 116, which is close enough.  So to double the distance we need three additional flashes.

If you think about it, it sounds excessive. To go from 6 inches to 12 inches you need three more flashes of the same power. But if you were at 20 feet and were going to 40 feet it would not sound as bad. The point is it is a law of physics and that is how it works.

However if you think of it backwards, at half the distance you need 1/4 of the light. (same rule) So the plan is to move the flash closer and that is why you see all kinds of macro flash brackets that move the flash closer to the subject. 

Please note the examples above were done with a Canon 580 EX II with the GN of 190 feet. Dedicated macro flashes guide numbers are nowhere near this. Canon's MT-24EX has a GN of 24 (78 feet) and the MR-14EX has a GN of 14 (46 feet).

Ambient Light

Always be aware of the background and what will reflect back on the sensor.

One thing about flash and it is really cool once you understand it is that it always works with what light is available. So, if your camera settings don't allow for the current light to get a good exposure only the new added light (flash) that is reflected back is used. For instance there is a flower with nothing behind it (well close behind it - this is a common flower technique) and the camera is set at a fast enough shutter speed and small enough aperture not to get anything exposed in the background when you fire the flash only the light that bounces back from the flower is recorded. This can give you a properly exposed flower with great depth of field with a black background as nothing else was reflected back.

So if you don't have something close behind your subject it will have a black background.  This may not necessarily be bad but sometimes it is undesirable. Keep in mind that if you lower your shutter speed and start to use ambient light you can get camera shake in. Also keep in mind this is based on photographing live bugs in the wild not a studio so the photographer has to make a decision as to what combination to use.

One of the most difficult insects I have found to photograph is a spider in a web. They usually don't have anything close behind them, a flash will blow them out or not be powerful enough to capture detail against the black background. One way around this is to shoot them into the sky and use the flash as a fill flash to capture their detail. 

 

 

Some Examples of Bugs shot with Flash - All the Photos in the Gallery were shot with Flash

 

macro shot with C-Bracket Flash

This spider was on a screen on a bright day with all the light behind him. The C-Bracket manual flash setup (shown on the next page) was used to illuminate him. This shot was made in a fully manual mode and without flash a totally impossible shot. The flashes were cheap $10 units that were not adjustable and they were rated with a duration of 1/1000th of a second. It was this flash unit that taught me about flash duration. I could still get camera shake in the image and I was using a 200th of a second plus the flash.  So neither the flash nor the shutter speed was removing it.

macro shot with auto flash and bracket

This spider was on the side of a light grey house in the dark shade and was shot with a fully automatic E-TTL flash mounted on a bracket with a softbox.

Macro Ring Flash example

This spider was on the side of a car and shot with an automatic Ring Light Flash (you can tell by the reflection in its eyes - this is the undesirable part of a ring flash - reflective surfaces) Size wise he had a leg span of about 3/8's of an inch

To sum up flash, you are going to need to learn how to use it to get good shots consistently in any lighting situation. All of the options listed work and work well. Without question a dedicated macro flash is the best as it is the easiest to use, carry in the field etc. If it is not in the budget (usually isn't), and you have a flash already go for a folding bracket that has the ability to lock in place, add a softbox, a ball head or angle bracket (you can bend them) so you can adjust it downwards and an ETTL cord.

With flash it is really just practice, you will find quickly that you will be able to dial in manual settings, fire off a flash and be real close to a great exposure. The more you practice the sooner you will be able to get it within a half a stop just by looking. If you have trouble seeing it in the viewfinder look at the histogram. The reason I say you will be able to easily dial it in is because at f/11, ISO 100 and 1/200th of a second usually no ambient light will make it to the sensor. Therefore the flash is always providing most of the light and it is predictable just like in a studio. When you think about shooting a portrait in a studio you set up the lights, pose the person and take the shot. If you want another portrait, you put the next person in the same spot and photograph them, the lighting will still be correct. Here it is the same, if you are at maximum magnification you will be at the same distance to your subject and if your flashes are mounted to the camera they will also be at the same distance at the proper angle.

Continue to Macro Flash Brackets