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A Prototype Light Pipe

 
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Bob



Joined: 26 Feb 2008
Posts: 17
Location: The Sea Ranch, Ca.

PostPosted: Thu Mar 06, 2008 8:13 pm    Post subject: A Prototype Light Pipe Reply with quote

Being new to macro photography I quickly found that the lighting of a subject can be quite challenging. I therefore decided to experiment with methods of piping light from my flash onto a subject. My objectives:

• Uniform illumination of a subject 10” to 20” in front of the lens
• Have the light coming from above subject
• Have the light converge onto both sides of the subject
• Be able to select side lighting from either side
• TTL metering
• The light pipe must be light and easily portable

Attached are several images of my crude prototype light pipe. I made it out of 4 ply mat board. I covered all the inside surfaces with aluminum tape for reflectivity and obviously taped the assembly together with duct tape. I lined the inside of the part that slips over the flash snout with the Velcro (wool side only) so that it is a snug fit.

When I want to block the beam from one side I just hold a peace of black card in front of that opening.

For an initial test I set up a ½” diameter foam ear plug at the near focus limit of my 100 mm lens. I then took a series of exposures at f/16, 1/250 sec. with the ports open or closed as indicated.

I then replaced the ear plug with a wood netsuke and then a quarter. For the quarter I added a 1.4X extender and a set of three extension tubes. Both ports were open for these exposures and I used the same exposure as before.

I have not done any Photoshoping of these images other than changing size.

I have since taken my prototype into the field and photographed some small flowers (I will post them in the Macro and Close-up Gallery.) An advantage that I had not thought about is that the small aperture and fast shutter stop all movement of the flower caused by the wind. And, I can control the lighting to simulate natural lighting.

My conclusions after very limited testing:

• TTL metering works perfectly. Correct exposure every time.
• The light gets scrambled sufficiently in the tube that diffusers at the ports are not required.
• This design meets all of my design objectives
• The prototype works well enough that I doubt I will make a final version until this one gets damaged beyond patching.

As I stated, I am new to this form of photography and any and all comments and/or thoughts on how to improve this design would be very much appreciated.

Bob




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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19970
Location: Richland, Washington State, USA

PostPosted: Thu Mar 06, 2008 8:45 pm    Post subject: Reply with quote

Bob,

That looks like a great setup you've put together. Thanks for posting out such a comprehensive set of photos.

Just offhand, I have no idea how to improve this design. I'll be interested to hear comments by other members who have played more with this sort of thing.

I notice this is your first image posting, so be aware that I tweaked it to fix a formatting problem. The issue is that when there is no newline between the end of one image tag and the start of the next one, as in
Quote:
...[/img][img]...

then some browsers display both images on the same line, right next to each other. That makes essentially one very wide image, which causes the text to wrap very wide also, and pretty quick, the whole page becomes unreadable. The fix is to just be sure that each [img] starts its own line, unless of course you intend to do side-by-side display of narrow images. The only tricky part is being aware of the problem, because if you're using one of the browsers that don't do this, you'll never even see it.

Again, thanks for the info about your light pipe. Looks like it's working great! Very Happy

--Rik
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Bob



Joined: 26 Feb 2008
Posts: 17
Location: The Sea Ranch, Ca.

PostPosted: Thu Mar 06, 2008 8:49 pm    Post subject: Reply with quote

Thanks for fixing my formating problem. I had noticed it but did not know what to do about it.

Bob
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puzzledpaul



Joined: 06 Aug 2006
Posts: 414
Location: UK

PostPosted: Fri Mar 07, 2008 2:22 am    Post subject: Reply with quote

<< I'll be interested to hear comments by other members who have played more with this sort of thing >>

Raises hand from 'back of class' ... having just returned from a 'comfort break' Smile

Bob - I was using something very similar for most of last summer / autumn last year, having decided to adapt the approach used on the item described in linked thread.

(I didn't have an external flash at that time)

Although my 'light pipe' ... (tended to refer to this as a splitter / diverter) is intended to address the same issues, there's a few differences - whether 'better', is another matter Smile

Mine looks narrower - but deeper - 200 x 80 mm front port area (overall size when viewed from 'business end')
Basic contruction is folded cereal packet cardboard - strengthed with paper mache
(I use a piece of free 3D modelling s/w to mess around with ideas and also lets me produce 'folding patterns' / developments - not necessary with stuff this simple, but am used to same (see profile) )

Outboard reflecter surfaces @ 45deg to match internal 'splitter.

Barn doors (adjustable) to allow for 'aiming' of light.

All relevant surfaces covered with Ali kitchen foil.

Ports covered with kitchen towel diffusers (in an effort to stop ali foil texture being visible in certain (very reflective) situations ... eg bubbles being blown by flies.

Device is a push fit on end of flash - I wrap a piece of cardboard around flash head first (as sleeve) then attach rest to that (makes changing diffusers easy when messing about / experimenting)

Whole lot weighs about 25 - 30g (had to pre-load kitchen scales to get it to register Smile )

Used on a Canon 550ex, which is mounted on a home-built flash bracket / arm.

Few real-world (non-test) situation problems i found when using mine, with a 100mm macro lens ... esp with extn tubes.

Size of the thing -
Can disturb adjacent branches etc causing subject to clear off.
Temporarily cast shadow over subject ... as above.
Access issues in general - easy to forget width - esp. in dynamic situations / rotating whole cam rig to change composition etc.

Really needs some sort of rig for maintaining orientation when used in portrait mode ... good reason for bracket, imo.

If using diffusers - be aware of thorns etc Smile
I'd now use tyvek instead of kitchen roll.

Currently not in use as am (mainly) using an mpe65 at the moment - and the closer wkg distance (esp at higher mags) presents other issues - but I have considered making another (smaller, less wide) splitter just for this lens ... considering the size (or lack of) real estate to be illuminated @ 3x and above Smile

Since it's not usually good manners to post pics in other ppl's threads, I'll leave it at that for now, unless you don't mind / want me to?

pp


http://www.photomacrography.net/forum/viewtopic.php?t=998
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Bob



Joined: 26 Feb 2008
Posts: 17
Location: The Sea Ranch, Ca.

PostPosted: Fri Mar 07, 2008 10:44 am    Post subject: Reply with quote

It looks like great minds think alike. Wink

Obviously there are many ways to accomplish the same task. I think I will "borrow" some of your design ideas if I ever redesign/rework my assembly.

Please feel free to post any pics or other comments in any of my threads. I am here to learn as I assume most people are so the more info the better.

Thank you for thoughts.

Bob
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puzzledpaul



Joined: 06 Aug 2006
Posts: 414
Location: UK

PostPosted: Mon Mar 10, 2008 10:24 am    Post subject: Reply with quote

Apols for delay - real world getting in the way and was on a roll with something else am currently making - also didn't have any pics of the beast in question.



Fairly self explanatory, but fire away if you have any Qs.
Mine isn't angled downwards as it was always intended to be used with a flash bracket.

Since it's the results that're also likely to be of interest - here's a few from last Sept > Oct ish time.



All uncropped, Canon 10D + 100 macro + tubes + 550ex.

Added the full size pixel crop of the bubble, as can see the 4 areas ... the 2 'ports' + the reflector caught bits.

I added the barn doors after seeing how much light was being lost - whilst messing around ... yours, being wider might be inherantly better - but poss worth checking?

Anyway, hth / of use Smile

pp


<< It looks like great minds think alike. >>

Well, the 50% at your side of the pond might qualify ...
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acerola



Joined: 13 Dec 2006
Posts: 251
Location: Hungary

PostPosted: Mon Mar 10, 2008 11:13 am    Post subject: Reply with quote

I like both of them. Very clever. The only problem I have with them, that in my rucksack they wont last for a month. Do you have a collapsible or inflatable design? Laughing

So I go closer with the light source. I have a reflector on the built in flash with a wire frame. That produce different light, than these with fever control, but it is usable. My second camera is in repair, so I don't have picture.

I also thinking on using a macro bracket. And external flash to get closer to the subject.

Do you consider to go closer to the subject? If the source is closer to the subject, the lighting is came from a bigger surface from the subject point of view. Your design may be produces pictures with more contrast and a little harsher. And maybe it can produce gleams in a shiny surface. Its the matter of taste and the matte of subject. I like the even lighting better.

The sample pictures are good, anyway.
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puzzledpaul



Joined: 06 Aug 2006
Posts: 414
Location: UK

PostPosted: Mon Mar 10, 2008 3:41 pm    Post subject: Reply with quote

<< Do you have a collapsible or inflatable design >>

If I was in your situation and still wanted to use one of these designs, I'd seriously consider (as I have done) making one out of tinplate - something like baked bean tin matl.

Suitably stiffened / constructed, it'd be more than strong enough to withstand such treatment ... and still be very light.

<< So I go closer with the light source >>

As do I, using the macro bracket (also home-made) I use, whether with the splitter described here, or what am currently using with an mpe65.

<< I also thinking on using a macro bracket. And external flash to get closer to the subject. >>

An excellent idea - in both cases.

<< Do you consider to go closer to the subject? >>
See above - yes, am already doing this. The bracket I'm using lets me place the flash head a considerable distance in front of the lens front element (as well as just about anywhere else)

I think Bob's comment in his first post is about spot on :
<< quickly found that the lighting of a subject can be quite challenging >>

Couldn't agree more ... and when seeing some of the results by various ppl on these forums, just emphasises how much (more) there is to get to grips with Smile

Thx for the 'pic' comments btw.

pp
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Bob



Joined: 26 Feb 2008
Posts: 17
Location: The Sea Ranch, Ca.

PostPosted: Mon Mar 10, 2008 6:25 pm    Post subject: Reply with quote

Paul,

I like the “barn doors” on your design and from your photos it obviously works very well. I will think about adding using this approach if I ever incorporate a blocking feature and/or a set of diffusers.


Acerola,

Durability and packing for travel will be problem but on the other hand it was easy to make and the materials are next to free.

As for getting close to the subject, the image of the quarter above was taken with a 100 mm lens at minimum focus and a set of three extension tubes. I do not know what the working distance was from the front of the lens but it had to be rather short. I think the addition of diffusers would allow one to get almost to the front of the lens (I will try this in the future).

I agree that the bright reflections are distracting and should be eliminated if possible. I will test the impact of using diffusers on reducing the hot spots from reflective surfaces. I think it should help but I do not know how much.

Bob
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acerola



Joined: 13 Dec 2006
Posts: 251
Location: Hungary

PostPosted: Tue Mar 11, 2008 6:39 am    Post subject: Reply with quote

Paul, I wanted to address the question about getting closer more like to Bob. Smile But anyway what kind of flash bracket do you use. I'm very interested. I did not find a suitable one yet.

Bob, the best way of diffusion is increasing the light surface, either getting closer on putting on a bigger diffuser.
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puzzledpaul



Joined: 06 Aug 2006
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PostPosted: Tue Mar 11, 2008 8:35 am    Post subject: Reply with quote

<< But anyway what kind of flash bracket do you use. I'm very interested. I did not find a suitable one yet >>

acerola - I've not seen a commercial one that does what I wanted of mine (am not saying one doesn't exist ... just that I've not seen / found one Smile )

... and I probably wouldn't have bought one even if I had ... 'cos I like messing around in the workshop Smile

Good results can be had by all sorts of different designs, 'cos at the end of the day it's more about the person using the kit, than the kit itself, methinks.

Lord V (Brian Valentine) uses video light brackets (from memory) and achieves excellent results.

I intended to start a thread sometime re what I've been mucking about with - but not just yet ... sorry ... I'd just prefer to have finished all of the bits first ... and have actually used same for the intended purpose first Smile

pp
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acerola



Joined: 13 Dec 2006
Posts: 251
Location: Hungary

PostPosted: Tue Mar 11, 2008 8:51 am    Post subject: Reply with quote

Yes I saw that design (LordV)
Thanks, I'm waiting for it. Thought I don't have workshop, and a DIY bracket might over my capabilities.
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acerola



Joined: 13 Dec 2006
Posts: 251
Location: Hungary

PostPosted: Sun Mar 30, 2008 12:06 pm    Post subject: Reply with quote

I finally bought a flash bracket. I like it at first sight. I did not tested it in the field.
You can see it
here.
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puzzledpaul



Joined: 06 Aug 2006
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Location: UK

PostPosted: Sun Mar 30, 2008 12:40 pm    Post subject: Reply with quote

Hope it does the job ok Smile

May I ask how much it weighs?

pp
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acerola



Joined: 13 Dec 2006
Posts: 251
Location: Hungary

PostPosted: Sun Mar 30, 2008 1:47 pm    Post subject: Reply with quote

It's 248g in my kitchen scale. The ballhead is not too strong, but it can be changed to a stronger one.
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