Lighting help

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Marci Hess
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Lighting help

Post by Marci Hess »

It's winter again and I'm back to trying to figure this out. Last year, I got the microscope objectives and acoutrements along with the StackShot so am set there. (Many, many thanks to help from this site!!) I didn't get time to play with this before the "growing season" hit and I was in the field. So I'm back at it. I've played with just the objectives but am struggling with the lighting. I have a speedlight. I've tried using additional lighting on the sides. I keep reading about needing diffused light which perplexes me because using direct light is still not providing enough light. I even created a cardboard studio with white interior to direct the light. The sets up photos I've seen on this site don't suggest that lots of intense light is necessary. I'm thinking I might not have the right light? I don't think the speedlight is going to be the answer as it won't flash as fast as the StackShot will require. Without buying and testing tons of light options, is there something you can suggest?

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Post by rjlittlefield »

Hhmm... I'm struggling to imagine what's going wrong for you.

Normally electronic flash can provide way more light than is needed, and as a result it ends up getting turned down to low power, like 1/8 or 1/16. At such low power levels the flash will recycle quickly and batteries last a long time. Even adding a lot of diffusion by bouncing the flash off something or shining it through some diffusers usually leaves the flash operating at far less than full power.

What speedlight are you using?

--Rik

Marci Hess
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Post by Marci Hess »

I'm using Promaster 7500EDF. I did get ONE decent picture after a lot of various changes with the flash. If I've it right, it will be uploaded into this message. This was NOT taken using the StackShot and that is my ultimate goal so with that, won't I need a continuous light source?

Marci Hess
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Post by Marci Hess »

Image

Charles Krebs
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Post by Charles Krebs »

A quick search turned up your flash unit. It should have more than enough output for your purposes. Are you sure you have the flash mode set to "M"? What power level is set (bottom right corner of LCD screen on back of flash)? There are 7 power level settings. You can choose from full power (1/1) down to 1/64. When you use manual settings be sure that you set your camera shutter to the flash sync speed (or a longer shutter speed).

A quick photo of the way you have your flash and diffusion set-up would help.

Marci Hess
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Post by Marci Hess »

I have M set for 1/1 but I couldn't get enough light so I flipped over to Multi 1/16 with a -2 report and that's when I got enough light to take the photo. I had the flash pointed just as I do in the picture. The difference is that I had the insect setting out and not in the "light studio." But...the photo I'm attaching is the speedlight set up and the "light studio" that I want to use so I can diffuse the light (stop the specular glare) and use my StackShot. Since the flash won't be able to "keep up" with the StackShot, won't I need to find a continuous light source?

Marci Hess
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Post by Marci Hess »

Can't seem to get it included in my reply e-mails. Sorry.

Image

ChrisR
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Post by ChrisR »

M set for 1/1 but I couldn't get enough light so I flipped over to Multi 1/16 with a -2 report
That's repeat - but doesn't add up.
2 x 1/16 is 1/8, so whay is your 1/1 not way too bright?
Does it look bright?
I'm wondering if you have the flash set in some Command mode so it's only sending out a triggering flash, to non-existent other flashes?

the timing of the Stackshot won't be a problem, you can set it to wait a long time between shots. But it shouldn't need to be long.

The diffuser though - off to photoshop...

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Post by rjlittlefield »

Marci Hess wrote: This was NOT taken using the StackShot and that is my ultimate goal so with that, won't I need a continuous light source?
No, it's very common to use flash when shooting with StackShot.

The only disadvantage to flash is that you have to take a picture to see what effect it's going to produce, where with continuous illumination you can just look at the live view.

In exchange, flash has the advantage of very short effective exposure time, typically less than 1/5000 second when used at low power as for our applications. This means that it freezes out most of whatever vibration may be present.

Perhaps you're worried about the flash having to go off 100 times while you're shooting a 100-frame stack. It will definitely do that. But again, the flashes that I'm familiar with will be running at low power and will have no trouble shooting fast enough for stacking.

At this point, I think the big question is how to set your flash and camera so that they work the way they should.

On the camera, you want to be running in Manual mode, with shutter speed around 1/200 second (whatever is your camera's fastest normal flash sync speed).

On the flash, it's also Manual mode (M). (According to the manual's description, you do not want Multi mode. The function of Multi is to make the flash pop several times per frame, "to record the flowing motion of a subject" [manual, P.6].)

With those settings, 1/1 M should give you the brightest image (probably overexposed), 1/2 will be not so bright, and so on down to 1/64. Just choose the one that works best, erring on the side of underexposure if you have to compromise.

--Rik

Marci Hess
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Post by Marci Hess »

Yes, I meant "repeat". Let me "take it from the top" tomorrow and make sure the flash isn't in any odd mode. You don't like the studio set up? It is something new I'm trying in hopes of avoiding that harsh white glare while providing a nice white background.

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Post by ChrisR »

When I've used a light tent like that, it's either had monster strobes around the outside, or a flashgun or two bouncing around the inside. I can't remember how much power it sucks up, but it can be a lot, I think. I don't know if what you've made would be good for very small subjects.

More conventionally you'd use a remote flash cable and put the head near a diffuser near the subject. The "sky" to the subject has to be a big angle, it doesn't matter how far away it is from it. (So for small enough subjects, you can use a table tennis ball as the diffuser).
What you could try with a some of that material you have (or kitchen towel is good) near the subject, and some curved or flat white card or paper or Al foil (here shown blue) as a reflector could be something like this. It's still not as efficient as getting the head right up close but for low magnifications, should work

Image

Marci Hess
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Post by Marci Hess »

Thanks!! I believe I've found the sweet spot for the flash now but really need to work on reducing that glare. To that end, if I understand this correctly, having the flash off the shoe and to the side would be better. Is that correct?

I'm guessing my next questions will come with I couple this with the StackShot!!!

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Post by rjlittlefield »

really need to work on reducing that glare. To that end, if I understand this correctly, having the flash off the shoe and to the side would be better. Is that correct?
The key to reducing glare is this: do not let the subject see the flash directly.

Instead, you want to illuminate the subject indirectly, using light that is either bounced off a white reflector or run through a white diffuser. In either case, the flash and reflector or diffuser need to be positioned so that light reaches the subject from a wide range of angles instead of a narrow range.

It is simplest to think of this from the standpoint of the subject.

In the setup that you have shown above, what the subject sees is a concentrated bright light coming directly from the small flash head, surrounded by dim light bouncing off the walls. It's like what you would see if you were standing in a white room and somebody took a picture from outside the door, using a flash unit pointed straight at you.

The glare is a reflection of the light coming directly from that small flash head.

In contrast, look at the illumination setup used by the USGS Bee Inventory and Monitoring Laboratory, described HERE, shown in pictures about half-way through the document (also accessible HERE and HERE). In their setup, the flash units are used to illuminate the inside of a white enclosure (a styrofoam cooler, in their case), and the subject is illuminated entirely by light bounced around the inside of the enclosure. The strobes are mounted and pointed in directions such that the subject can't see them directly at all.

The USGS setup is more like what you would see if you were standing in a white room and somebody took a picture with flashes pointed at the walls.

When the flashes are triggered, it's effectively the walls and ceiling that light up. That's what you want. Make the walls and ceiling light up.

--Rik

Marci Hess
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Post by Marci Hess »

Rik - This is incredibly helpful and makes sense! Put this in the FAQs! Thank you soooooo much!

ChrisR
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Post by ChrisR »

Yes we could add it. A very simple version is there already: http://www.photomacrography.net/forum/v ... hp?t=25935

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