Back to Ganoksin | FAQ | Contact

Photographing Jewelry - Macro aperture range


#1

Hi all,

I just bought a used Canon Rebel Xti. My Sigma 5omm 2.8 macro lens
of 2.8. (Sigma has told me that since it is an old lens this is the
only way that it will sync up with the digital body.)

I am really a moron when it comes to understanding photography. (I
rely on the fine services of my photographer to document important
work such as anything intended for publication, jurying, etc.) I
intend to take technical shots for teaching (which I have done with
this lens and my old school 35mm.) and for documenting work when I
can’t get to my photo guy.

So my question: How important is it to be able to have the full
aperture range?

Thanks.
Andy


#2

Hi Andy:

For teaching shots, you need the full range. (and the old lenses
weren’t designed to deal with some of the odder requirements of
modern digital sensors.) Yes, it’ll mount, but it won’t work with the
rebel as well as a newer lens, even in image quality.

New macros aren’t that expensive. Canon makes a 60mm macro that’s
pretty good, and floats around used for about $300 the last I
checked. Remember that the sensor on your rebel isn’t full frame, so
a 50mm lens is going to act like a 90mm lens. (or thereabouts.)
(It’ll appear to be zoomed in much more than you remember.) I use a
90mm Tamron macro that I really like. New for about $500 or so. Used?
dunno. Consult the oracle at eBay.

The only drawback is that sometimes I end up shooting from feet away.
(if the piece is big.) Rings & etc, from hand-held range, but use a
tripod (!).

FWIW,
Brian.


#3
How important is it to be able to have the full aperture range?

For 3D objects, it’s pretty important, Andy. The whole question is
one of depth of field. If you were using the macro lens to photograph
flat documents or something, it wouldn’t matter, but for 3D things,
being able to stop down the lens to a smaller aperture, while it
increases the exposure time, also increases the depth of field.
That’s the range of distance from the lens within which things are in
acceptable focus. With a wide open lens, only a narrow plane will be
focused, and anything closer or farther is out of focus. Stopped
down, you can get much of a small object in focus. And example would
be a ring. If you want a close up shot where the top, like the stone,
is clearly focused, and you’d also like the shank and back of the
ring recognizably focused instead of being a dim blur, then stopping
down the lens to a smaller aperture is a requirement.

A suggestion. Try using your camera in full manual mode. Don’t worry
about it syncing up. You set the aperture to a small figure, as well
as the focus, manually, and the exposure time. Just like with your
old 35mm. If the camera doesn’t have the ability to give you exposure
suggestions when used like this, just use trial and error. Slow till
you get an idea of what exposures work, since you have to go and look
at each image to see how it looks, but with the in camera review of
digital images, this is a lot simpler than waiting till 35mm slides
come back. Once you get an idea of the usual exposure settings for a
given lighting setup and camera settings, just bracket several
exposures around that typical setting, and one or more should be
fine.

I bought a Pentax digital not long ago for a similar reason. Back in
the old film camera days I rather liked an old Vivitar 100 mm macro
lens I’d gotten that gave way better images than it’s price would
have suggested. My new camera only does limited things with this
totally manual lens, but it’s enough. The lens works as well as ever.
All I really give up is all the auto stuff the new camera does that
my old 35mm cameras didn’t. Otherwise, it’s still quite capable of
using the lens, and I’d bet your Canon can do most of this too. If
it cannot determine from the lens where your aperture is set, and the
camera doesn’t have a “depth of field preview” button, then simply
take the exposure reading with the lens wide open, which you say the
camera WILL do, right? Then use math to determine the approximate
setting for a smaller f stop. It’s straight linear math. If your f
stop (aperture is half the size (larger number), then the exposure
setting needs to be twice as long. thus, going from an f2 to f4
would double the exposure time. f4 to f8 would do it again, and so
on. Most likely, you’ll want to be shooting between f8 and f16 or so,
to get acceptable depth of field. Some items might need even smaller
apertures. That sometimes needs a quite long exposure (and a good
tripod), and then you run into oddities of the sensitivity of the CCD
sensor, so sometimes you have to make adjustments, but once you
figure out what settings to use, it will remain roughly the same if
the lighting is the same…

Hope that helps.
Peter


#4

It’s everything. At F2.8, the lens is wide open. You will have
minimal depth of field, the very opposite of what you need. Spend
$400 and get Sigma’s 105 mm Macro. This will give you one of the
finest pieces of glass in the world, a wide range of f stops and a
working distance of around 13-14 inches. Worth every penny. Sell the
film camera and macro lens, maybe you can get something for it,
somewhere. Trade in at Ritz Camera, maybe?

I have access to a lot of different cameras, but chose to write
"Jewelry Photography Made Easy" around the Canon Rebel (xT or xTi). I
chose that camera and the excellent Sigma 105 mm macro for a reason.
You’re a small step away from being in VERY excellent shape Andy, so
please consider the 105 made for the EOS series camera like you now
have.

Wayne Emery, long time admirer of your work


#5

The smaller the aperture, the greater the depth of field in macro
photography. You really want to be shooting small items such as
rings at F22-F32, depending on the optical sharpness of the lens.
Macro lenses are specifically designed for close up photography. They
are sharp at small apertures, and designed to focus to 1/2 actual
size or even 1:1. I find that a 60-90mm macro lens is the most
useful, because the focal distance from object to lens is far enough
to allow good lighting.

Rick Hamilton


#6

Hi Andy.

It sounds like you are mostly doing documentary photos, where the
important thing is to show the subject clearly. Your lens should be
fine for that kind of work, as a rule. The one thing that might be a
problem is depth of field, which is the range of distances from your
camera lens where the picture will be in focus. The rule is, the
larger the aperture number (smaller aperture,) the larger the depth
of field. For example, an f/5.6 aperture will allow you to focus on a
deeper region than an f/2.6.

You can use this effect to sharply focus on a particular area of
interest, while allowing the rest of the subject to be slightly
blurry. This only becomes a problem if you are shooting a large
finished piece and want the entire image to be in sharp focus, as in
product photography. Your photographer probably uses an aperture of
f/11 or smaller with very bright lights to get professional results.

In short, for your purposes your Sigma lens might be fine the way it
is, and it will let you shoot good pictures in relatively dim light.
Your pictures will be sharply focused in only one area, though, and
will be more or less out of focus for anything even a couple of
millimeters nearer or farther away.

Regards.
Steve
Gems Evermore
http://www.gemsevermore.com


#7

Hi

The whole depth of field thing can be reduced to a bit of math.
Cinematographers call this the “circle of confusion” with its
related math. I got the formulae out of the cinematographer’s
handbook. Every kind of camera has a certain "circle of confusion"
number to put in. My formula is based on 35mm SLR cameras or their
digital equivalent. If you call Nikon or Canon they can give you the
number for your point and shoot.

If anyone wants this clever little excel spreadsheet just ask me off
line. You input your aperture, distance to the subject and your focal
length. This then tell you exactly how far the near and far borders
of crisp focus lies.

Now, this stuff gets as arcane as anything we do in the jewelry biz,
but I really love being able to put the data in and see what I can
get for depth of field rather than finding out when I look on the
monitor, or worse after prints are made.

Daniel Ballard