Clarifying Laser Output Power and how this relates to photography.

[clansley]

The idea seemed solid but now they are on the desktop I'm less convinced; but that might be the lighter background confusing the brain (they may have come out better if it had been dark in the room).

Laser is 520nm. Nothing done to images except set white balance to daylight (was on auto and they were very different) and convert to jpg. The background is black!

[click on image for full size]

f16 52mW:


f11 26mW:

 

[kingphoto]

The idea seemed solid but now they are on the desktop I'm less convinced; but that might be the lighter background confusing the brain (they may have come out better if it had been dark in the room).

Laser is 520nm. Nothing done to images except set white balance to daylight (was on auto and they were very different) and convert to jpg. The background is black!

[click on image for full size]

f16 52mW:


f11 26mW:

Yeah, I see what you mean. Unfortunately the background being 1 stop brighter has made this particular test inconclusive as you suggested. If you have the time and inclination it would be great to see the same results in a pitch black room (with matt black material in background if you have any). With my beam tests a few weeks back (because I was primarily interested in the beam) I found the best results were achieved by having the laser just to the side of the camera pointing away from camera towards the center of the frame/lens. That way you only get the beam spot on the wall, not the bright laser aperature. It's hard to tell from your photo's but it looks like you have pointed the laser back towards the camera although I could easily be wrong. Thanks so much for your efforts so far, they are really interesting. I only wish I could join the party...but Im still trying to decide what laser/s to get. Unfort Jetlasers PL and HL's 100-200mW are currently out of stock. Despite being expensive, these are probably the best lasers for me. Cheers, Mark

 

[clansley]

[Just checked out your website - very cool work]

Repeated in darkness.

Attempts to get near/at point of over exposure:
[52mW] f16, Iso3200, 30 seconds:


[26mW] f11, Iso3200, 30 seconds:


Alternative settings:
[52mW] f8, Iso400, 30 seconds:


[26mW] f5.6, Iso400, 30 seconds:


SMOKE (kind of hard to be consistent)
[52mW] f11, Iso200, 15 seconds:


[26mW] f8, Iso200, 15 seconds:

 

[kingphoto]

[Just checked out your website - very cool work]

Repeated in darkness.

Attempts to get near/at point of over exposure:

SMOKE (kind of hard to be consistent)
[52mW] f11, Iso200, 15 seconds:


[26mW] f8, Iso200, 15 seconds:

Hi there, Sorry for the late reply - mothers day duties on Sunday. Thanks so much for doing another test on black in a dark room. I know these things take time so appreciate your efforts greatly. I think they all look great and I would have to say that it seems that halving output power is directly related to photography ie if you halve output power and give your capture +1 stop of additional exposure then it look like you get back to where you started (beam exposure-wise). This is great to know and helps greatly with me deciding what output power laser to purchase. I am not sure what the 4 to 6 times theory is about and it would be great if one of the more experienced laser members could help explain this. But for now I am happy.

Just one point and only saying this to help and in case you ever do more camera tests (and in no way taking away from your efforts an assistance in helping to understand output power in photographic terms - which has been exceptional). I also should have mentioned this in an earlier post. I personally find when doing these types of tests it is better to adjust the exposure duration/time ie if 30 seconds was your first exposure then the next with the 1 stop nd filter would be 60 seconds. If this were to create too much noise then you could then open up your f-stop ie go from f8 to f5.6 say. That would mean your first exp was 15s and 2nd (with nd) 30s etc, or increase ISO to get exposure time down. When you adjust the f-stop during the test a few things change ie depth of field (which affects focus so if your focus wasn't spot on the beam could appear wider or thinner in the 2nd frame). Also, the way the light hits the sensor because it is traveling through a smaller/larger aperture/hole. So time is always the most consistent way to do these type of tests if noise is not too much of an issue. If it were, there would be no reason why you couldn't shine the beam parallel to the lens or even on an angle and open up the aperture to let in more light ie f5.6/f4 etc. Hope this helps and once again thanks so much for all the time you put into testing and retesting this over the weekend. Cheers, Mark

Oh, and thanks so much for your comments on my work...very kind of you!

 

[joeyss]

I have T3i dslr and magic lantern AWB I'll have to try this out with my 40 mwish blue ray and my 475mw one

 

[kingphoto]

I have T3i dslr and magic lantern AWB I'll have to try this out with my 40 mwish blue ray and my 475mw one

Great, the more tests the merrier. I have just had a comment from an experienced member that we need to ensure we know the exact output rating of our lasers (while testing) for these tests we are doing to be valid. It was a good point. So please make sure the lasers are metered if possible and the output is verified. Thanks for showing an interest and we look forward to seeing your results! Cheers, Mark

 

[kingphoto]

[Just checked out your website - very cool work]

Repeated in darkness.

Attempts to get near/at point of over exposure:
[52mW] f16, Iso3200, 30 seconds:


Hi Clansley, Are you confident the ND filter was in the same place/rotation...halving the lasers output for all the shots in your tests?. Just trying to establish if the half power achieved with filtration was consistently accurate. Thanks, mark

 

[clansley]

I wouldn't publish any of my results in a scientific journal! Errors are possible everywhere. My thoughts on it were that even this test should be able to tell if the 4 times the power for double the brightness holds for cameras or not. I did the test not expecting any specific answer so was surprised by the result. Without a real LPM and a real way of comparing the exposures I don't think any test result will be solid. It's a pity the senior member did not want to share their view in the open, so helping us all.

I had the filter clamped so it would not have rotated but the hoz angle between it and the laser may have changed between testing and photographing. If you and the senior member have ideas on how to make the test more useful (even without a real LPM) then I'll do another test.


Thanks for the tips on the tests, it hadn't occurred to me that the depth of field would matter. Your photographic skills could be useful on this forum!

 

[kingphoto]

I wouldn't publish any of my results in a scientific journal! Errors are possible everywhere. My thoughts on it were that even this test should be able to tell if the 4 times the power for double the brightness holds for cameras or not. I did the test not expecting any specific answer so was surprised by the result. Without a real LPM and a real way of comparing the exposures I don't think any test result will be solid. It's a pity the senior member did not want to share their view in the open, so helping us all.

I had the filter clamped so it would not have rotated but the hoz angle between it and the laser may have changed between testing and photographing. If you and the senior member have ideas on how to make the test more useful (even without a real LPM) then I'll do another test.

Thanks for the tips on the tests, it hadn't occurred to me that the depth of field would matter. Your photographic skills could be useful on this forum!

I personally think the tests were really good so thanks so much for doing them. Its always hard when you don't have all the gear like LPM's etc...but I think you improvised really well. No worries about the tips, ask anytime, happy to share my knowledge. Mark