Flowers - Up Close - EXTREME DOF Part 5

This is the fifth and I think final post about close-up photography of flowers, insects, etc...  If you haven't read the others you can live on the wild side and read this one first or go back and take them in sequence.  If DOF brings to mind Department of Finance and EXTREME makes you think we are headed for another bailout, then you really need to go back and start at the first post.

What I am going to talk about in this post is nothing short of magic.  Anyone who has worked in closeup photography knows that there are limits to what can be done with focus and DOF.  While writing the other posts I hoped that everyone understood that all I talked about carried an unspoken warning label "Within the physical limits of the lenses ability to focus".  There are definite limits to how much DOF you can get no matter how small the aperture and the limit increases as you move closer.  Sometimes the best DOF at f45 is not much thicker than a dime.

Here is an example and it is not even really extreme.  I am nowhere near 1 to 1 macro yet even at f22 the DOF will not carry across even the front flower.  Forget about sharp focus across both flowers.

As I mentioned in an earlier blog, my point of focus was about half way into the front petals.  At f22 the best I could do was to get the front petal and part of the center of the first flower into focus.

Selective focus like this can result in very beautiful images and I do it on purpose often to create soft flowing images.  This shot might even work better with a more open aperture because as I stopped down to get greater DOF I also got more background clutter.

Too bad you cannot have it all, deep DOF to fully cover your main subject AND shallow DOF to keep the background soft and unobtrusive.  Well....welcome to the wonderful world of digital!  You really can have both with a process called focus stacking.

So what is focus stacking???  It is simply a procedure where you take a series of images with different points of focus then blend them together in post processing to create one image that has impossible DOF.

All you need to do this is a calm day with little or no subject movement, a camera solidly mounted on a tripod, and post processing tools.  I use Photoshop CS4 but if you don't have Photoshop you can purchase free standing packages that do the work for you.  Helicon Focus is one of the more popular ones but there are several others.

I took 8 images and blended them together in Photoshop to create this next example.

In the first image I got the tip of the closest petal in focus then for the next 7 I carefully moved the focus point back until by the 8th image I was well back into the second flower.

Notice two things, first all of the front flower and most of the second flower are in focus, second the background is soft, much softer than in the single image shot at f22.  The reason for all the softness in this second image is that all of the 8 images were shot with the lens open to f5.6.

In addition to no subject or camera movement there are a couple of other rules.  You should shoot the images in order front to back and input them into the software in that order.  You should also be very careful to leave no out of focus areas as you move back into the subject, make sure there is overlapping DOF.  If you do not overlap the DOF you will have bands or waves of focus and unfocus which look very unnatural.  Shooting at an open aperture makes it harder to overlap the DOF and requires more images and more processing power.



Here is an example of a flower I shot at f3.5 and blended 13 images to create the final image.  Take a close look at this totally impossible depth of field.

If you have Photoshop CS4 here is how to do this. 

1.  Open Bridge and select the images to be merged, in the correct order. 
2.  Click on "Tools" --> "Photoshop" --> "Load Files into Photoshop Layers"
3.  Photoshop comes up with each image in a separate layer shown in the right side panel for Layers
4.  Select all of the images
5.  Click "Edit" --> "Auto-Align Layers"
6.  Select "Auto" and click OK
7.  When that process is complete click "Edit" --> "Auto-Blend Layers"

Auto-blending layers may take a few minutes, LOTS of processing going on here.  This step reminds me strongly of waiting for an image to come up in the black & white darkroom.  You will have an out of focus image on the screen while the computer works and then, just like magic, the image will resolve itself into something beautiful (we hope).

After all that, you will have an image that probably needs some cropping to clean up the edges and it may have some ghosting that needs cleaning up, especially if there was ANY movement of subject or camera.  You will need to flatten the layers before you can do any serious processing to the image.

Just for fun, here is one more example of the power of focus stacking:

First image is soft and flowing.  I shot it with a Nikon 105 macro wide open to f3.5.  Not very much is in focus, just a very shallow area in the center of the flower.  Background is very soft and undefined.

This second image was shot with the same lens and camera position but the aperture was stopped down to f22 to get greater DOF.

This one has most of the flower in focus but the leaves in the background are also becoming more distinct.  I liked the softer background better so this final image was a focus stack of 8 images all shot at f3.3.

I left just a little bit of ghosting around the large petal that is front and center so you could see what it looks like.  Here is the best of both worlds, I have the flower totally and impossibly in focus with the background soft and unobtrusive.

Life is good......Later!

Flowers & Insects Up Close - Part 4

Well... I slipped in "& Insects" this time because I have a couple of great examples of using flash with insects.  If this is the first post you are reading, it is actually the fourth in a series on Close-Up Photography so go back a few posts to start at the beginning.  This post will deal with using flash.  I did a series on understanding light in early June so if you have never heard of the Inverse Square Law or don't really understand "fill light" then go back to the three part series I did on Understanding Light before tackling this post.  Here we go.....

In a perfect world the natural light would always be beautiful and we would never need to change it.  Too bad we don't live there.  You can OFTEN improve the lighting balance on your subject and background when working in close-up photography.  I think that close-up photography offers more opportunity to manage the light than any type of photography that is done outside the studio.  Remember the Inverse Square Law?  In the examples I gave we measured light travel in feet and talked about how it falls off as it moves out from the source.  In close-up photography we talk about measuring light travel in inches not feet but the same principles hold.  When you are lighting things that are inches from the flash it does not take much power and you have LOTS of control within arms reach.

So what do you need to get started?  Digital camera with a hot shoe flash that will work OFF the camera.  Yep, that is the first necessity - get the flash off the camera.  Many of the newer flash units work off camera wirelessly but an old fashion hot shoe cable will also work.  I find the off camera cable to be so easy to use that I still use it even though my flash and camera will work wirelessly.  Flash power is not a major issue because you are working so close to the subject.  Instead of looking for a powerful flash, be sure to get one that gives you lots of ability to control the power and to turn the power down.

Lets start with the easy stuff - fill flash.  How many times have you found a great subject, flower or insect, but had the light coming from behind.  With back lighting you usually end up with the subject underexposed and the background correctly exposed or the subject exposed correctly but surrounded by a badly overexposed background.  Fill flash to the rescue!!

I tried everything to get this guy to turn around and face the light but no luck.  The background looks great but the subject is underexposed by 2 or 3 stops.

Pop on a flash and place it about a foot from the subject and to the right of the camera.  Turn the flash down to about -2 stops using exposure compensation on the flash unit.  Set the flash mode to Auto TTL.  The result is dramatic!!

I shot this with a Nikon 70-300 zoom with a close-up diopter on the zoom for closer focusing.  The camera was about 3 feet from the subject and on a tripod.  The background was a pink azalea bush in bloom in early May and it was about 4-5 feet from the subject.

Lets first think about the lighting on the subject verses the background in both images.  The background lighting is the same in both images so the flash had no visible effect on the background.  One reason for that is that the flash was 1 foot from the subject but 5 or 6 feet from the background.  The Inverse Square Law states that every time the distance light travels doubles, light falls off by two stops.  Based on that, the light that the flash put on the background would be 4 to 5 stops less than the light it put on the subject.  Not really noticeable.

Why not just leave the flash on the camera?  Any flash is powerful enough to light this insect from 3 feet away.  I want the flash off the camera because I want more control.  I want to control the direction of the light.  I also want to control the lighting ratio between the subject and the background.  Here is the second big thing to think about - you control exposure for the subject with the flash, you control exposure for the background with your selection of aperture and shutter speed.  You need to think about the two as completely separate exposures taken at the same time.

Here is another example to illustrate the level of control you have using flash for closeup photography.

The first image was shot without flash at f22 with a shutter speed of 1/6 second.  It is badly underexposed for the subject.  The second image was shot at f16 with a shutter speed of 1/25 second with flash.  The flash correctly exposed the subject.  The aperture/shutter speed combination allowed for 1 stop less background light in the second image (aperture was +1 but shutter speed was -2).  Notice the difference in the background exposure?  You are making two independent exposure decisions when you use flash in closeup photography.  I held the flash less than a foot from the subject.  It was set to auto TTL mode and I dialed down exposure compensation on the flash to -2 1/3 stops.  The flash correctly exposed the subject then turned off.  The background was exposed based on the aperture/shutter speed combination.

Here is a more dramatic example of the same subject.  In this example I kept the flash set to -2 1/3 stops but changed the aperture/shutter speed combination to f45 for 1/13 seconds.  That is 3 stops less than the original exposure and 2 stops less than the second exposure.  Look at how much control you can have over the lighting ration between subject and background!

So here is the third thing to think about.  In both of the examples I have had a subject where the background was several feet from the subject.  I placed the flash a foot or so from the subject, exposed the subject with the flash and the flash had very little or no effect on the background lighting.  What happens when the background is closer to the subject as in 1 to 1 1/2 feet from the subject.  When the background is a foot or so from the subject you have to do something that very few photographers do.  You have to get the light VERY close to the subject, I am talking 3 to 5 inches!  When I shoot flowers I am always on a tripod.  I hand hold the light while looking through the viewfinder and put it as close to the subject as possible without getting the flash into the image.

Think about this - if the flash is 2 feet from the subject and the background is 1 foot behind the subject then the light on the background from the flash will be about 1 stop less than the light on the subject.  If I move the flash to 6 inches from the subject I can lower the light from the flash on the background to -3 stops.  That is lots of control!  Here is an example where the background is close to the subject and is brightly lit.

I think the background is a little distracting in this image.  My solution was to add flash placed very close to the flower.  The first image was shot at f16 with a shutter speed of 1/15 second so I increased the shutter speed to 1/60 second.  This darkened the background by two stops and made the flower stand out from the darker background. 

So go out there and play with you flash unit!  There is lots of potential for great images and you have a huge amount of control over light in closeup photography.  Have fun and experiment.

Here are a few technical notes that I should leave you with.  I am a Nikon user so most of what I talk about is based on my experience using Nikon camera and flash units.  The Nikon flash is set up by default to correctly expose for the subject without trying to manage the background.  If I want the system to try to balance lighting between subject and background I have to put the flash in a special "BL" mode.  My experience with Canon flash units is that they are by default in a balanced lighting mode so you may need to set them up differently to make all this work properly.  Check you flash instructions but you may have to put your flash in manual mode and set the power yourself.  I am sure that some of the other camera systems from Pentax, Olympus, Sony, and the list goes on....may also have different requirements.

For camera setup, I usually go to manual and set both aperture and shutter speed manually.  The flash is in Auto TTL mode and it handles exposure for the subject as I am selecting aperture and shutter speed combinations to get the look that I want for the background.  My selection is seldom what the meter system recommends for correct exposure.