How to take effective laser spot test pics with phone cameras?

Hi All,

So the Form1+ has issues with laser flare, and central to understanding those issues is getting a clear picture of a particular machine’s “laser spot profile” - or a “spot shot”.

Unfortunately taking a good photo of the laser spot test through the Form1 cover is actually very difficult.

The purpose of this thread is to try and determine a simple process to get reasonably consistent pictures of the laser spot test to share.

please submit your methods…

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The before/after shots of mine that I posted on the other thread where from my phone laying on top of the orange hood. It worked well because it controls the distance between multiple pictures. As long as some features of the printer are visible, scale and orientation are givens.

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What about the paper you used? What phone do you have?

I have a Nexus 5, and in the end I found that I just could not take effective pictures through the F1 cover; I had to lift the cover and take pics through a cheapo orange filter on top of tissue paper

It was normal printer paper, I don’t know the specs. The phone was an iPhone6 that time. I found if it lays on the hood the auto-focus can’t get confused by the hood.

ok - so the shot underneath? - actually, I think the quality there is lacking. It’s enough to show that your choke is doing a great job, but the clarity is not there to show if the brighter part of the laser flare is on the “rabbit ear” side, or the “carrot” side…

You’re right, it’s not perfect. On the original post you can blow up the picture though.
Same picture enlarged:

:slight_smile: yes the zoomed image is an improvement - but I still think there’s a lot of detail missing there.

cf this image, which I think is poor …

Perhaps this is just too difficult a problem…

My method is exactly what Josh described. Laying my iphone on top of the cover and taking the picture. Regular laser printer paper was used. Works pretty good.

@Monger_Designs don’t recall the image - sample?

@KevinHolmes It’s really difficult to take a good picture of light. Digital camera sensors get confused. If you want a better photo, then the paper has to be not white. Perhaps a dark blue color paper or dark green will work good. The issue is, that it will most likely block out the faint flare from coming through.

This one was taken using the HTC One phone. The first Form1+ I received

This one using the Iphone 6. The second replacement Form1+ I received

@Monger_Designs hmm - useful - but on par with @JoshK’s pic above - I was hoping for a procedure that would achieve better detail than mine from above… although your iphone 6 pic is probably very clear when zoomed…

As you say though - taking pictures of light is not easy …

One interesting thing to note - which I picked up before - is that your “pure evil” part of the flare as per @JoshK’s post in the other thread - is on the same side as the rabbit ears - in contrast to his and my flare “profile”

I have a unique laser spot. Congrats to me lol

The funny thing is, that I can print just fine in the middle of the build platform or away from the hinge, however close to the hinge is when things start to distort and fuse together.
The left one is on the side of the platform away from the hinge, the center one is in the center, then the right one is close to the hinge side of the platform.

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which is what I see too - although flaking always occurs - where ever I print

This might be in part due to beam going out of focus / decollimating as the distance from the laser to the vat increases (as you go closer to the edges of the print area).

Anyway, regarding taking photos…
The laser spot simply has too high a dynamic range for a phone camera.

The amplitude between the darkest and brightest parts of a spot is too huge for a typical phone camera sensor. What might help is to take TWO photos, one exposed for the halo, one for the hotspot. That is, of course, if your phone’s camera app allows you to tweak the exposure (AE compensation) or tap to trigger AE/AF.

Yeah - I’m thinking it just can’t be done with a phone camera without opening the cover - which it seems makes some people nervous.

So I’m now wondering about my run-spot-test against drop/blob of resin on perspex on in empty tank idea. Perhaps that’s a simple standard method to get good pictures of laser spot profiles …

Without the cover on, it’s nigh impossible, because auto exposure algorithms on typical cameras + the gamut of the sensors are a complete mismatch for the color of the spot / laser.

Unless you put a piece of filter above it, like you did in your videos, that is.

Or laser protection goggles.

yeah - I found it impossible without the filter - but @Steve_Johnstone managed it somehow - but still with the case open, and in any case he actually showed that it didn’t work with one of his phones.

I’m currently waiting on a print so I can’t show the whole procedure yet - but this is what I propose

  1. cut out a piece of overhead transparancy - with a notch or mark on one side to mark it’s orientation, say the front side.

  2. put a blob of black resin on it

  3. put a clean empty vat in machine - run spot test and note location of spot

  4. put transparency with blob in vat over spot location and run spot test twice

  5. remove transparency and rinse in IPA

  6. take pictures of cured resin blob - which has shape of laser spot profile