Beamshot usefulness

vt2nv · 2018-08-21T20:23:09.000Z

Beamshots may be useful for comparing power levels with a single light, and for beam-width and beam-spread analysis, but it seems to me that, lacking standards, beamshot usefulness ends there.

There are a few serious considerations-

Exposure duration and ISO. Is exposure set to render a properly exposed image with the light operating at full power? We have all see beamshots with blown-out highlights,. Beamshots from a mediocre light will look fabulously bright when ISO is increased or when the shutter remains open long enough to blow out the highlights.

White balance There is no “true” white color temperature. My clients insist on perfect color rendition (I do tabletop product photography as a side business) . I shoot a piece of white paper and white balance to that, which usually winds up being close to 5000°K. I work in adobeRGB color space. Jpegs out here use sRGB color space, which white balances closer to 6250°K or so. Lacking standards, it is almost impossible to render a beamshot with accurate color rendition, but it is possible to get really close

Defining what is white My external hot-shoe flash is the Canon 600 EX-RT. I know the temperature of the flash, and when I photograph a white surface with flash I have a pretty good way of assessing the white point. Easy as pie.

Then there is gamma to consider. This can quickly become a slippery slope…

Use familiar standards: At the very least, use control limits to assess beam intensity. The lower control limit (LCL) can be a dim light source we’re all familiar with, something like a 2AA incan mag. The upper control limit (UCL) can be a bright light we’re all familiar with, maybe automotive highbeams. A TN20 would do the trick. So would a Thorfire S70s or similar (bright lights I own) . Next: expose for the highlights of your brightest light. Then, without changing camera settings, photograph the light being evaluated with it illuminating the same white target you white balanced to. Even the cheapest electronic flash will specify its color temperature.

I have seen reviews using these, or similar, methods to assess intensity and color temperature. Photographs that are well done and useful.

Beamshots taken with a camera set to auto exposure and auto white balance, and evaluative metering, that some guy takes with a light pointed at a garage door has little value to me. I have also seen wonderful properly taken beamshots. C’mon, if you can go into a light and mod it, you can certainly learn how to twiddle a few knobs on a camera.

I’m not accusing anyone of being intentionally misleading, this is a nice community, everyone here is genuinely friendly and informative. A rare thing for internet forums. What I am saying is that for beamshots to be a truly useful tool, a bit of photographic knowledge, combined with standards, would go a long way.

I’ve been thinking about this for a while. Thank you for allowing me to share my thoughts.

[harry steps off soapbox now]

Cheers

c

BlueSwordM · 2018-08-21T20:27:14.000Z

When I take beamshots, which I rarely do, I usually set the minimum ISO on my camera to get the lowest noise possible, then adjust the exposure to the brightest light to make seem on the limit of overwhelming the light balance.

I also set the color balance so it looks exactly how I see the light color temp.

Enderman · 2018-08-21T21:27:11.000Z

Most people just do them for fun, not any scientific comparison or test.

Of course if someone uses auto then it will be far from the real appearance, but many people use proper DSLR/mitrorless cameras and adjust the exposure and iso and colour balance and other stuff to get the image as close as possible to what they see with their eyes.

This isn’t perfect since people have computer screens calibrated differently and with different brightness but it’s about as close as you can get to giving the other people the real life experience.

AgentWhiteBread · 2018-08-21T21:37:05.000Z

While I don’t mind, I know what you mean so I started taking shots myself. I don’t have many so far because I was bothering my neighbor so I’m in the process of securing a warehouse in an industrial district for taking pictures. I’m waiting until I receive my BLF GT mini.

Here’s my old album: Beamshot comparison, outdoors, ISO 640 1/10s exposure. - Album on Imgur

DominikM · 2018-08-21T21:52:41.000Z

Since I’m doing beamshot for almost 10 years I can write some things, the settings are one thing, but the second and almost the biggest factor that You did not mention is the weather… The reflectivity of the materials changes drastically when they are wet or even moist - at the same settings, in the same place you can have totally different beamshots.

low clouds if you are living in the city
markings the ground
aiming the light at the same place etc…

Basically the beamshots are unique for the photographer and you only can compare the beamshots made by the same person, and sometimes they still can be misleading.

My standard’s are as follow :
Outdoor : 2s, f3.5, ISO:200 WB:5000K
Indoor : 1/8s, f3.5, ISO:200 WB:5000K

vt2nv · 2018-08-21T21:56:17.000Z

Point taken. I take photography seriously, and I’ve been at it for a long time. I know an overexposed or over-processed image when I look at it, others may not. I would hate to think that a noob (like me) would plunk down upwards of $300 to purchase a light based on over-exposed beamshots. That is a good initiator of buyer’s remorse.

Cheers

Enderman:

Most people just do them for fun, not any scientific comparison or test.

Of course if someone uses auto then it will be far from the real appearance, but many people use proper DSLR/mitrorless cameras and adjust the exposure and iso and colour balance and other stuff to get the image as close as possible to what they see with their eyes.

This isn’t perfect since people have computer screens calibrated differently and with different brightness but it’s about as close as you can get to giving the other people the real life experience.

vt2nv · 2018-08-21T21:59:10.000Z

Like I said. Work in adobeRGB and white balance at 5000°K. Your camera settings look very good to me, as does your technique. My friend, you know your stuff.

Cheers

DominikM:

Since I’m doing beamshot for almost 10 years I can write some things, the settings are one thing, but the second and almost the biggest factor that You did not mention is the weather… The reflectivity of the materials changes drastically when they are wet or even moist - at the same settings, in the same place you can have totally different beamshots.

low clouds if you are living in the city

markings the ground

aiming the light at the same place etc…

Basically the beamshots are unique for the photographer and you only can compare the beamshots made by the same person, and sometimes they still can be misleading.

My standard’s are as follow :
Outdoor : 2s, f3.5, ISO:200 WB:5000K
Indoor : 1/8s, f3.5, ISO:200 WB:5000K

Jack_Kellar · 2018-08-23T10:32:36.000Z

shrug I just use beamshots to check out the beam profile, so I’m not overly bothered. I do get gutted when an idiot shines a thrower on the garage door… from INSIDE the garage :person_facepalming: