Asking what FIXED mm for a macro I hope is not what you mean. fixed
means one point only.
What I think you mean is what is the depth of field for a macro
Depth of field is simply put the portion of a picture/image that is
in good focus. The sharp clear portion we strive for. This for any
lens is dictated by the rule of thirds. The rule of thirds is again
simple. It is breaking the focal distance that a certain lens will
capture into thirds.
If the focal distance is 1 inch, the first third of an inch will be
out of focus. The middle third of an inch will be in focus, and the
last third of an inch will be out of focus. Now comes the part of how
do you know what the depth of field will be for a given lens.
Telephoto will give you the greatest/longest depth of field. In
essence it will have a focus to infinity if all variables are done
correctly. While a macro lens will have the shortest DOF. There are
macro lenses that will have as little as a half inch DOF. So your in
focus portuion will be a millimeter or 2.
How do you manipulate the depth of field? Again that depends on your
lens. The best DOF comes from stepping down the arpeture. Which
means closing up the lens. You can see this for yourself by making
your hand into a circle with your fingers. With one eye shut,
concentrate on a fixed point in front of you. as you close that
circle up, you will see the fixed point you are looking at becomes
more in focus. The same thing happens with camera lenses. On your
camera lens look at the rings. The one that clicks positions as you
turn it will be the one that controls the DOF. It will even have
distances marked on it (at least the old ones did). It is the ring
that will open and close the lens, or apeture settings. Thus it is
call the apeture ring. It is different from the free moving ring
that focuses the lens.
Now when you step down as it is called the lens you have the next
problem of light. The smaller the opening the greater the need for
more light. So you will set the timing of your camera for more to
compensate for the smaller opening. That is usually done with a
setting ring on the camera body itself. Each camera is different, but
it will be on the camera not the lens. If you have a camera that
meters inside itself. like popping up a small overlay of information
on the screen, or eye piece area, it will tell you what the DOF
setting needs for a time setting to allow enough light to come into
the camera. You might find out that the DOF that is best for you,
needs more light than your setting on your camera will allow. This is
where a good hand held light meter is best. It will allow you to know
just how much time is needed so you can over ride the max time
setting on your camera. (yes this is for a manual use not
computerized use of your camera). Why do I go on about time settings
that are not part of the lens? They work together. It is like flux
works with solder to alow the solder to flow when we heat it.
When you find out the best time setting which for most macro usage
will be in seconds, not part of a second. You will also need a good
Tripods steady the image capture. You hand holding the camera will
allow for minute shaking/vibration. No matter how hard we try to hold
our selves complete still, we will by nature of our heart beating,
have some vibration occur. Macro exstrapolates this vibration
greatly. This effects DOF.
With an extremely small DOF field it cn mean the difference of a
sharp focus shot, and a completely out of focus shot. Invest in a
tripod. Also along with this when working in macro is a good cable
release. Now what the hell is a cable release? It is a small cable
with a plunger end, that screws into one of the button of your camera
that you click to take the picture. Why do you need it? Because as
you click the camera, you again can cause vibration that will knock
you focus out of alignment. The cable with it’s plunger you push,
allows you to click the camera without the vibration. They are not
that expensive, and will save you massive headaches. Or if you are
good at jerry rigging things, you can build a mount that will hold
your camera completely steady. Hand holding is as they say, a crap
shot. So many variables come into play that it is best to just like
the pro’s get a good tripod (they don’t have to be expensive just
steady) and a cable release.
Now comes another variable. When you have what is called a shallow
or short DOF is where do you focus. and how do you focus. This is
where a hand held light meter really comes in handy. You want to look
at the picture you are going to take. So using the focusing ring,
enlarge the area you want to take a picture of. Study what would be
the leading edge of where you want to be in focus. As an example, a
ring. Say it has a prong setting. That first prong jutting out will
be the leading edge of your focus plain. Figure how much of tht DOF
will be the middle third.
This is going to tell you how much you will want your arpeture
setting to be. Now comes the puzzling part. Is that shallow DOF what
you want. It might turn out that stepping up the lens arpeture is
what you nwill want.
Having the smallest mm macro might not be what you really want. it
might be that you want 2 inches of in focus portion of the DOF. In
jewelry we have pieces that might when they are set up be more than
an inch wide area to be focused on. Study more about DOF field of
macro lenses for your camera. Find the lense that will have the DOF
field that works best for you.
Something that most don’t remember is what is the minimum distance
you can hold your camera to take the picture you want. For your given
lens, it should be on the arpeture ring. It will the shortest
distance printed on the ring. It might for a telephoto be 10 feet.
That means you would set up your camera and be at least 10 feet from
the subject of the picture.
For a macro it might be as little as inches. Do not get closer than
the smallest distance on your arpeture ring. No matter what you do if
it is exceeded, the picture will be out of focus. This is usually
what happens when you have a auto focus camera, and don’t realize the
distance does factor in.
Back to the prong setting image. Once you have studied the picture to
be taken and know the third you want, you need the time setting.
Since it is going to be a small area, look at the brightest point in
the scene. Look around you for a smiliar object that is larger but
illuminated the same way. For telephoto it usually is the sky. So
you would meter on the sky, closing out the rest of the secene so
that your meter will take in JUST the light area you want. That is
what will be put into the variables that you will set your camera
for. If nothing is around you, try the closest thing that appears
similar. After a while this will become second nature to you. It will
be easy to look at a given image and know what it will need for the
settings. Until that time you need to play with the settings using
these variables. Then there are the times you want more of the non
illuminated portion to be the focus. You will meter on the medium
lighted source. (this is what the camera itself would do when set on
auto. It is called center weighting. That is when a grey card is
helpful, but that will just confuse you totally.
Good lighting as you have now figured is important. It can screw up
or make possible that perfect shot. You want to eliminate all hot
spots, or bright spots on your piece. When you have a hot spot, it
will cause the rest of the picture to darken up and not show what you
want to be shown.
balance light will give you al the scene to be in focus, and shown
so it wont be blacked out or washed out. You need to look at the
piece you are photographing. What are the lightest and darkest spots
before you add light. When you set up your piece, whre does the light
land? Does that light source give you harsh points of light on the
object. If it does you need to eliminate those hot spots. Thus
softening your light source. You will need difusers on your main
light. This can be as easy as a piece of white gauze fabric (its
cheap) over the light source. Not on as bare bulb, but fixed so it is
very near, but not touching the bulb. Yes you can use a standard
light bulb for this in sa normal lamp stand. But this just gets the
front of the piece. You want the sides also illuminated. This takes
some lights from various positons, so many lamps with gauze in
These lamsp can be the cheap $10 versions from WalMart. In fact they
usually have those half bullet shaped metal housing around the bulb.
Now you have all but the back of the piece lighted. For the
background, and this is just as important as the foreground, use
bounce light. When metering you will find that black can be brighter
than white. Pick the background you want. now take a piece of
cardboard maybe (but not exact) 16x20 inches. cover it with the shiny
side of aluminum foil outward.
Below the table, glass, stand what ever you have your jewelry piece
set up on, place the aluminum cardboard sheet. You will need an extra
lamp. You will point the lamp at the cardboard. you can move this
cardboard so it will bounce the light off the background. This will
light it up, This bonce light will also give you a very soft glow
bounced back at your piece to give it just a nice non shadow effect.
If you do not have a solid surface your piece is set up on, you might
want the bottom to be unlighted. But then again if you are
photographing a piece where you want to show off the ability for the
stone or enamel to glow with light, it will help to have a very
difuse (thicker gauze) lamp below as well.
This probably gave you more questions then answers. It is years of
classes, and workshops. I’ve known and worked with the greats in
photography, but trying to encapsulate all of it in a short post is
it’s own problem. Best words of wisdom, is to learn your lens, and
play with your camera to know what it is capable of. Ask more
questions, and this pea brained old lady will try to help.
Aggie, suffering from a bout of typing diarrhea