Nice results using a ring flash!

[hengefjes]

Hi all!
I just wanted to share a tip that might come in useful to some of you. I've been working a lot with close range photogrammetry in low light situations, and have grown tired of rigging lights and hauling that tripod around. I even used handheld lights to paint light into the shadows during long exposures - which worked nicely as long as the fundament was sturdy enough to cope with the movement. I bought a Godox AR400 ring flash. It has a built in battery and quite powerful led light for focusing. It enables me to shoot at iso100, f8, 1/200th sec, with my 20mm fx setup, and still get fairly decent exposures at 20 feet distance. The result I get with this setup is by far good enough for my use, - it also makes the shooting process very quick compared to using a tripod. You can find some examples of using the ringflash in my sketchfab gallery: https://sketchfab.com/gunnar/models

[ekbmuts]

Pretty nice!  Thanks for the tip.  I too am tiring of 2-4 second exposures because I can't create enough ambient light in my studio...

Jon

[Bartlett]

I had similar success with a pair of flashes that clip to the end of my lens.  I was concerned that changing the direction  of the   light source for each photo would confuse the program, but the result was very good.   I had the part on a gray background, and I was firing shots as quickly as I could position myself.

[ekbmuts]

Okay, I'm in.  Now where do I get my hands on one of those ring flashes....

[hengefjes]

I got mine from "godoxstudio" at Ebay.com

Heres the flash and specs:
http://www.godox.com/EN/Products_Camera_Flash_Witstro_AR400_Powerful_Ring_Flash.html

[ekbmuts]

Great, thanks.

I'm on this!

[hengefjes]

Hi again, everybody!
I got asked the following question in a private message:

Thanks for your post about using a Ring flash when taking photos for photogrammetry. I was wondering if you could describe your setup in a little bit more detail?

I see you are using the Godox AR400 and a 20mm lens. After some digging on your SketchFab site I think I saw you were using the Nikon D610? Lastly, the cross polarzing technique you are using. Did you buy some linear polarizing film to place over the ring flash, and you were able to cut it to fit?

Thanks a lot for your post, it is encouraging to setup and I just want to make sure I got all the details to try my hand at it.

I'll share my answer here in case someone else want's to know:

My setup:
Camera: Nikon D610 - would rather have a D750 as the D610 spits oil on the sensor when shoothing upwards - the problem stopped at around 25000 shots though. D750 has slightly better low light performance and includes wifi which I find handy in some cases.
Lenses: Nikkor AF-S 20mm f1.8G for large objects and interiors, - for smaller objects I'll use one of these; Nikkor AF 50mm f1.8D, Nikkor AF Micro 60mm 2.8D, Tokina AT-X 100mm f/2.8 PRO D Macro. I used to have the 14-24 f2.8 Nikkor which was fantastic for photogrammetry, but it was just too heavy...
Flash: Godox AR400 with the Godox wireless USB trigger. The trigger will be swiched with a sync-cable to save some weight.

Cross polarization:
With this technique one can minimize the reflection from the flash and avoid glare form shiny surfaces. You light the object with polarized light from the flash. To polarize the flash I ripped the polarizing film off an old broken LCD-screen (all LCD-screens have polarizing film on them), and taped it onto a clear piece of plastic which then was cut to fit the front of the Godox flash. The direct reflections of the polarized light on the object are filtered away with a correctly adjusted regular polarizing filter on the lens. I use a "B+W Circ.Pol.Nano KSM 77mm" on the 20mm. Works great, but steals a couple of stops from your exposures - so don't expect to use this on larger distances than 4-5 feets.

[scaron]

@hengefjes
Thanks for the follow up information.

[AdrienB]

I'm doing one ring light for my 82mm diam. ( 24-70mm ) sigma with 3x100w LED For something around 80€

It's a little bit heavy ( around 800gr/ 400g fanless [ if its ok ] ) and my 40D + Sigma around 1.5kg.

3x LED ; 3x booster 12-35V ; 1x power supplies 240>24v 20A; 3x Ventirad ...

I've 3Dprinted a foot button to use it like a flash.

i'll do a front filter with " plexyglass diffusant " ( http://www.rapid-catalogues.com/plexiglass/product706_plexiglas_blanc_diffusantmax_3050x2030mm.html ) when i'll be very close to the object.


It will cost me 100€ max
Everything is ready, i'm just waiting the LEDs !

[hengefjes]

Sounds very interesting! I hope you post pics of your rig, and results. I've tried different homemade diffusors, and the larger they are the better, but there is a limit to how practical it is when your ringflash is 2-3 feet wide.  There is a very nice fairly affordable chinese ring diffusor on the market thats foldable, but the build quality leaves much to be desired, and its to weak for my use with one of my Nikon SB800 flashes. Very nice for macro work though. https://www.amazon.com/RoundFlash-Universal-Collapsible-Magnetic-Diffuser/dp/B00NQ6UT4W

[DocPopi]

@hengefjes hello, thank you for all this information. I've asked my company to buy me that flash, but I kind of struggle to have good results with it. I mostly have problems of fall off, with too much contrast and directional lighting on the object. I f I crank the power of the flash up, it ends up overexposed.

I was wondering what power you were setting your flash on while shooting? I mostly work around 1/16 - 1/32, with f22, ISO100-250 and shutter 1/60

Thank you and I hope you're still around 7 years later!

[Alexey Pasumansky]

Hello DocPopi,

You could probably find useful the information regarding the ring-flash from the following video:
https://youtu.be/c7tI6ICo23I?t=572
Even it is used mostly for the material scanning, some tips are good to know.

[DocPopi]

Hey Alexey!

Thank you for your answer, sorry I hadn't seen it before.

I'll have a look at the video (I have an indoor setting though, not oudoor, sorry I should have mentioned that before)

Best