Vibration

When you're doing something as exacting as macro photography, the mechanical action of the shutter itself is enough to introduce vibrations that affect the quality of the shot. Ray demonstrates this above, by having the shutter act before any light whatsoever is allowed to fall on the coin.

Thing is, Canon has had that problem already solved for years in some of their dSLR's, including every Rebel since the 450D. Canon uses an electronic first shutter - nothing mechanical happens whatsoever with the first shutter.

With dSLR's the shutter is not the aperture snapping open and closed. It's two "curtains." The first, top curtain is closed when you snap a shot, while the second, bottom one is open. When you hit the button, the first shutter slides open from left to right, allowing light through. The second then immediately follows, closing from left to right, and the actual opening through which light actually flows is more like a slit proceeding across the subject than an actual full opening except for long exposures.

It's that first shutter snapping open that causes the vibrations. The second shutter also causes vibrations, but only at the end of its' travel when the shot is complete anyways.

Since the Canon uses an electronic solution for the first shutter, the vibrations which Ray found a solution for do not happen. I would expect Ray's second, clearer shot to be the "usual" result from a Rebel-series dSLR.

Keep in mind, Ray, I think only the Rebels use this feature automatically. With the 7D, it might be a menu selection - "Quiet Shot."

If you're going to get that obsessive about things, you'd still want to use the same technique as you did to originally eliminate the vibration above, so that the presence of light is completely disconnected from any shutter action whatsoever. That being the case, the flash is unnecessary; the Jansjos will work equally well, you'll just use a longer exposure. With that said, I think I'd cover the lens rather than the light, especially if the lens is above the lights.

I believe the phrase you alluded to is "mirror lockup". It can come in quite handy for special applications such as this. On my older Canon DLSR, it is activated by way of a "custom function" in the menu. Although the new digital SLR's no longer utilize a "mirror" like the film cameras of days gone by, the term is still in use, albeit technically inaccurate.

Your mileage may vary.

That's quite a close up...Ray...Reminds me of your comment TO my post on lenses....and how I had it backwards......you are correct...in the full Macro state, on the bellows, the whole 15MP I can only get the first 2 digets on a Morgan dollar... I'm assuming your trust worthy 57D penny is the "Babe" shot here.....Stellar shot, didn't see the doubling before, or the green...copper spots as crisp as they are here
So I have to ask...this picture is with a 20MM lens....
I am assuming, your on the bellows.....thinking....?
by your results...the smaller lens.....the smaller lens
lets you focus on highly focused areas of a smaller area...wear as.. the larger say 105mm lets you see the whole coin?

Gene...that's exactly right. A short lens (20mm) needs to be VERY close to the camera sensor (20mm to be exact) to focus at infinity, while a long lens (105mm) needs to be farther away (105mm). This same situation applies at higher magnifications. To get to 1:1 macro, the 20mm lens only needs to be 40mm from the sensor, while the 105mm lens must be 210mm. This is why for higher magnifications, short focal length lenses are best to keep the bellows extensions reasonable...Ray

PS...but the working distance from lens to coin of the 105mm lens is going to be longer than the 20mm, so to get lighting flexibility you want long lenses.

Overall, I've found the best compromise for bellows extension and working distance for coins is in the 75mm-105mm range. This keeps the setups small and easy to work with.

The problem with the Canon 20mm macrophoto lens is the working distance. 20mm is not much to work with. To help with this they designed the lens with a 45-deg front slope to allow light to get in. 45-deg is not really the optimum but seems to be what most folks recommend for macro.

I think the lens is also at the lower limit of its magnification range. I had the PB4 bellows completely closed down for this shot. The 20mm is probably at its best around 10x. Perhaps I'll try it there and see what it can do. The earlier shot was at the Nikon's sweet spot of 3x.