Stupid Question!

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DaveW
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Stupid Question!

Post by DaveW »

Can I ask one of my stupid questions?

I notice all those doing stacking are using something similar to a massive milling table and shifting a large mass of precariously extended equipment each shot, whilst the tiny low mass subject remains stationary. Would it not be more stable to bolt down the extended camera equipment and just move the subject in sub-millimeter increments?

I cannot see that the limited amount the subject needs to move would make much difference to the lighting? If using a table tennis ball as a diffuser that could also move with the subject on some form of focusing slide? I presume there is some reason this method is not used, but would love to know what it is? :?

DaveW

augusthouse
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Location: New South Wales Australia

Makes sense to me also

Post by augusthouse »

Hi Dave,
I've been pondering the same question. I was having trouble finding a suitable milling/drilling table in Australia, so I decided to go for a Nikon PF-4 repro/copy stand that went for AUD$150.00 on eBay Australia (one of those rare bargains).

Basically I intend to set the camera where it needs to be for the photograph and move the subject using (at this stage) an ancient microscope/camera stand gizmo that I also bought on eBay. It allows for course focus (I'm working on the fine focus aspect). It also allows for backlighting and I'll use a dual fiber optic gooseneck diffuser for overhead lighting.

I'll eventually buy a milling/drilling table due the the magnificent results that Rik and George, for example are achieving.

When deciding whether to purchase the Nikon PF-4 copy stand something sprung into my mind in one of Charlie's posts about 'moving the subject to the camera'.

rjlittlefield
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Post by rjlittlefield »

For what it's worth, I ask the same question almost every day. :D

Speaking only for myself, I think the short answer is "available, cheap, flexible, and works good".

The last time I bought one of these machining tables (June'06), it cost under $100 US, new, shipping included. For this I get 6 inches of travel on two axes, calibrated down to 0.001" (25 microns) and usable down to about 5 microns per step.

Periodically I consider things like Edmund's linear stages.

But every time I do, I end up noticing that they have short travel, their movement per turn is not hugely better than my tabletop behemoth, and their controls are tiny and would be positioned dangerously close to the specimen unless modified. Then I would still need two more axes of fine positioning for framing, plus something attached to the stage for specimen holding. Add in the lights and a rigid frame, and I'm not sure how much smaller the whole package would be.

Certainly I have seen and used other equipment, especially in the field. I did the frost spikes by racking the front lens mount of a bellows, and this spider by tweaking focus on a macro lens, both with the camera supported on a mini-tripod next to a fixed subject. Charlie Krebs has done much work through a microscope, and his horsefly eyes were done by tweaking focus on a high magnification macro lens, with the subject's perch held in a small rack-and-clip mechanism screwed to the camera. One of my non-forum friends straps his specimens to the side of a microscope stage for shooting with an external camera.

All these approaches are viable, and I imagine that what's best depends on what's available and what work you want to do.

I keep coming back to the behemoth because I have it and it's flexible and easy to work with -- I get to fiddle with the subject and the lighting instead of the mechanics.

Besides, it's comfortable -- the handles feel just like the ones on my lathe and milling table. :wink:

--Rik

Charles Krebs
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Post by Charles Krebs »

A logical question really. Both methods work. I have one set-up that actually consists of an old view camera bolted to a hardwood base. For this arrangement, the subject is mounted on an old microscope focus mechanism, and the subject is moved back and forth. In other cases I move the camera... but it is usually fitted with short focal length lenses requiring rather modest amounts of extension.

When moving the subject you must be sure that the lighting does not change, and also that the direction of travel is straight on axis with the camera lens. Other than that, the end result is the same.

DaveW
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Location: Nottingham, UK

Post by DaveW »

Rik and Charles,

I understand about the milling table Rik, but it could equally be used under the subject itself. As to lighting Charles if flexible fibre optics are used the lighting unit could remain stationary, but the ends of the fibres can be fixed to the milling table or focusing slide because the amount of movement we are talking about here is negligible.

If I understand George Dingwall's set up, he was using studio flash so the light coverage would not vary much with the movement of the subject anyway.

If the problem is that it is a bit fiddly using the milling table with subject on at the far side from the camera, as I presume a remote release is being used on camera, there is no reason the whole set-up cannot be reversed with the subject on the milling table nearer the photographer and the camera away from them. The days of needing to use the wind on lever on the camera are gone.

Ideally, both the camera and subject should be on an optical bench with the focusing slide coupled to it. Oxford Scientific Films years ago were able to take many of their macro shots on a moving ship by using this method I understand.

Just a thought.

DaveW

georgedingwall
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Post by georgedingwall »

Hi Dave,
If I understand George Dingwall's set up, he was using studio flash
I no longer use flash on my focussing table. I added 4 x 100 watt fotofloods with dimmer switches. I found the flash difficult to control and there was some variability in output that had to be corrected in software.

I think the main reason that I prefer to move the camera rather than the subject is that, if you move the subject, you have a high chance of altering its position. A lot of these subjects, especially the organic ones can easilly move from the pose that you give them, and any movement of the subject stage would increase the risk that this might happen.

I think it is also worth pointing out that if you swap things around as you suggest, it is likely that you would have to move back an forth from the camera position to the subject position. I like to be able to sit behind the camera and review each exposure as it is taken. I know, roughly how many frames I will need to complete a sequence, but some subjects are difficult to calculate, and it is neccessary to keep shooting until you are sure that everything you want in focus has been captured. The extension of the system I use can be quite long, and it would be difficult to be behind the camera and to reach all the way to the other side of the subject in order to move it again. I would not be able to see the adjustment scale in that case, so would have to physically move to do it.

I'm sure that some setups could benefit from moving the subject, but for the sort of things I want to do, and with the equipment I have available, moving the camera is best for me.

Bye for now.
George Dingwall

Invergordon, Scotland

http://www.georgedingwall.co.uk/

rjlittlefield
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Post by rjlittlefield »

DaveW,

I understand about putting the milling table under the subject. It's an option that I have played with from time to time.

The problem, as you suggest, is ergonomics. No, I don't need to look through the camera while I'm shooting the stack, and in fact, I don't. My eyes are glued to the marks on the dial, as I tweak the screw and press the button on the remote release.

However, I still have to look through the camera to plan the start and end of the sequence, and to do the framing. If my camera supported continuous video out, I could use that, but video previewing is still a rare feature on DSLRs and mine doesn't have it. I suppose I could shoot pictures to focus and frame, and use video review to look at those. I haven't tried that, and I probably won't except as a last resort -- I'm expecting my shutter to die from overuse any day now as it is. Or I could point a video camera into the DSLR's viewfinder -- haven't tried that either but it's an intriguing idea.

I could physically arrange my equipment to keep the main screw handle close to the camera, but that would place it between the subject and the camera -- not the best place to operate safely or conveniently. Or I could stick in a right-angle coupling, or motorize the screw, or buy or make an NC table. (The latter would extend nicely to automation, but I'm saving that project for later.)

Reviewing your comments, I think your main concern regards vibration. Vibration is a very important consideration, particularly at higher magnifications. I had to do some re-engineering when I graduated from macro lenses to microscope objectives. If my bolted-to-the-table mounting rail had not solved the problem, I would have switched strategies and gone with solid mounting the camera and lens, despite the problems of ergonomics. It did, so I didn't.

As usual, the whole game is one of tradeoffs. My current setup has evolved under actual use, in response to a variety of pressures. I have frequently been surprised to discover that what I thought would matter, did not, and what I had not even thought of, did. But it's interesting and valuable to reconsider the options from time to time, so keep those thoughts and questions coming in.

--Rik

DaveW
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Post by DaveW »

Thanks for the comments and information and sorry for the delay in reply but my computer went down and was not fixed until today.

DaveW

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