Continuous lighting, no EFSC - what SS ?

[cadman342001]

Hi again,

I have a Nikon D800 and have been using it with an old mf nikkor 200mm f4 and various lenses reversed on the front - from 2X to 7X

I started with flashes (I have 3x yongnuo 560s) but now have 4 Jansjo LED lamps from IKEA.

Given that I don't have EFSC on my D800, what shutter speed range is a problem regarding vibration from mirror slap? (I've noticed that sometimes the fine detail is mush, sometimes great).

Would I be better off using less light eg only using say 2 jansjos and a longer exposure to avoid slap/vibration?

At the moment, I have the poor man's set up - the camera on a Proxxon table with added fine adjustment, the subject on a pin on top of an old 55 micro nikkor using the focus to raise and lower the subject, both mounted on a plank screwed to a heavy metal desk which is sat on a concrete floor.

I have a big heavy block of wood I could mount them on but I suspect the fact that they are both mounted to the same piece of wood means any vibration will be transferred across from camera to subject?

Cheers

Andy

[Chris S.]

Andy,

I use continuous light with other Nikon bodies that lack EFSC. I set a shutter delay of one second to let the mirror slap dissipate, then an 8-second exposure to eliminate the effect of shutter slap.

It's easy to determine experimentally how long an exposure you need. Shoot a series at 1 second, 2 seconds, 4 seconds, 8 seconds, and 16 seconds. If your results are like mine, you'll find that 1 and 2 seconds are terrible, 4 seconds is better, 8 seconds is better still, and 16 seconds is exactly the same as 8 seconds. If so, you might add 6 seconds to the series and compare.

I ran this test on a D700, and really should rerun it on the D7100 I use now, as I think its shutter slap is less, so I might be able to shave off a couple of seconds per shot. But each time I shoot, running that test would take more time than I'd save on that particular occasion. . . . You know how that goes!

My halogen illuminators have irises, which makes this test less fiddly than it might be with your LED lights.

--Chris

[mawyatt]

Andy,

I have an D800 as well, and went thru many different experiments with continuous lights (IKEA and many others), and strobes. I ended up with the strobes, which I use now. I routinely shoot at 5X, 10X and even 20X with a reversed Raynox tube lens with various microscope objectives.

At these magnifications vibration is a very difficult problem to totally eliminate, so you must work your way thru the various issues one by one IMO. Various techniques can be employed.

I use mirror up with a 2 second delay, followed by a 2 second exposure without any light except the strobe as the exposure, which is used as rear curtain trigger to reduce the front curtain vibration effects. I have measured the strobe light duration, it's a few milliseconds which is fast enough to help with low frequency vibrations.

This seems to work best in my setup which has the camera/lens on a Stack Shot focus rail bolted to a 120mm Al rail extrusion which is bolted to a 1/2" thick Al plate about 300mm by 1000mm, very rigid. The subject is mounted to a X,Y, Z positioner mounted to the same 120mm extrusion. This creates a system where the low frequency movements/vibrations cause the subject and camera/lens to move together and not have as pronounced effect on the exposure. All this sits inside a large light tent and the subject sits inside another smaller light tent, all to double diffuse the strobe light which comes from around the outside of the larger light tent.

I capture the images in TIFF format which takes the D800 about 5~6 seconds to create and have created a timing sequence to minimize the overall time between exposures. I have honed this down to about 10 seconds per exposure, having the camera/lens move during the D800 writing TIFF file time.

There are some inexpensive slave strobes that work well in this type setup, and free you from the battery issues with the Flash, although the size and convience of the Flash is great for this type of work. One drawback to the cheapest slave strobes is they are not adjustable, you must move them to adjust the light effective output. The Impact SF-AE56 and SF-AE80 are slave strobes and have stood up to my abuse, and for 20 & $30 respectively a bargain. I have had a bad experience with the Neewer 180WS adjustable strobes that are about $60, they are not designed for the type of abuse they experience with this type of macro stacking and will fail. The Interfit EXD400 are 400WS adjustable strobes can handle this type of work load, but cost $200.

Hope this helps.

Cheers,

Mike

[Chris S.]

Mike,

Note that Andy is already experienced with flash, and is looking to move to continuous light. Long exposures definitely eliminate the need for EFSC, at the cost of increased time to acquire a stack. They do this by making the first 1/8 or 1/4 second, when shutter slap is dissipating, a trivial contribution to the overall image. What Andy was asking was how long this sort of exposure needs to be. The answer is surely dependent on one's camera and the rest of one's rig, but 4-8 seconds is likely in the ballpark.

I have a big heavy block of wood I could mount them on but I suspect the fact that they are both mounted to the same piece of wood means any vibration will be transferred across from camera to subject?

Andy, this is actually the very thing you want--to mechanically couple the camera and subject, that if there is vibration, is is synchronized between camera and subject. Motion per se doesn't make images fuzzy--it's relative motion that does.

--Chris

[cadman342001]

So if I'm looking for 4-8 seconds that's cool, if I'm over exposed I just use less than the 4 lights yes ? or more diffusion material ? or close the aperture if I can (diffraction permitting) - depending on the magnification I'm using also I suppose

Will give that a go, cheers.

[Chris S.]

So if I'm looking for 4-8 seconds that's cool, if I'm over exposed I just use less than the 4 lights yes ? or more diffusion material ? or close the aperture if I can (diffraction permitting) - depending on the magnification I'm using also I suppose.

I'd avoid closing the aperture to avoid diffraction. Fewer lights may work. Additional layers of diffusion are fine. So is moving your lights farther from the diffusors. If the Janjos don't produce much heat, you can put something on them to cut down the light--a few wraps of facial tissue, a piece of printer paper, etc. A neutral density filter added behind the lens--or in front of the lights--also comes to mind.

I focus/compose with very bright light (irises open on the fiber optic light guides), then close these irises down for shooting. Mounting irises on your lights should also work, and be convenient and controllable. If the Jansjos are point light sources (I've never seen one), you'd want to spread the light before sending it through the irises. But that should be pretty easy.

Good luck!

--Chris