Topic: Annoying lighting issue

[lharby]

Hi, firstly apologies, I always seem to be asking buttheaded questions on here.

I have two softboxes which are rigged up via IR. I am certain when I got them they were brighter. In the image attachment you can see a dial which as I recall affected the brightness coming out of the flash. Today I shot using both of these and the dial setting made no difference.

Can they deteriorate over time? They were not particularly expensive so maybe it's time to upgrade.

As I am shooing large format I am starting from approx f8, although if I can make the scene bright enough it would be nice to shoot at much smaller apertures. I had the two softboxes relatively close to the object and was able to achieve f16 at 100ASA. The issue being most of my LF film ranges from 80 - 160ASA so I can't shoot using higher film speed (which is still an option with MF).

Anyone have any pointers?

[EarlJam]

My 20+ year old Comet monobloc strobes have a switch for "constant" or "variator" (variable) output. I don't see one on your strobe, but are there other switches on the body?

[Francois]

How old is the flash unit?
Both capacitors and the flash tube can deteriorate. The tube is affected by the number and power of the flashes. The capacitors go bad over time.
Could also just be a bad contact on the tube connections. I would clean those first with contact cleaner and go from there.

Tubes tend to go whitish (from memory) as they wear out.
Also, compare the output with and without the fabric on the boxes... hopefully there isn't a forgotten ND filter in them 

[Pete_R]

Not related to your question but I would, first off, replace that mains cable that is no longer safe.

Seems the model you have is one of the Chinese made strobes sold under a few different names. From what I've found the dial in the middle should adjust the flash output but if you have a manual for them I would check that in case there's some difference between yours and others. Also, from what I've found, looks like the GN is 36 (presumably meters) so it should be possible to calculate what aperture you should be using to see if the power is down. If you have a flash meter it would be easy to check the actual output against the spec (but remove the softbox first). you could also check if the power dial is having any effect.

[Francois]

Not related to your question but I would, first off, replace that mains cable that is no longer safe.

If the coating on the internal wires is OK, and there is continuity (which there obviously is) and that the wire doesn't become warm when charging, I wouldn't bother with it for now. If it turns out that the flash unit is going the way of the dodo, then the new one will come with some fresh wires.
But if the flash unit can be fixed, then investing in a new wire would be the first thing to do.

Safety first when it comes to mains power and big capacitors.

[Indofunk]

Not related to your question but I would, first off, replace that mains cable that is no longer safe.

If the coating on the internal wires is OK, and there is continuity (which there obviously is) and that the wire doesn't become warm when charging, I wouldn't bother with it for now. If it turns out that the flash unit is going the way of the dodo, then the new one will come with some fresh wires.
But if the flash unit can be fixed, then investing in a new wire would be the first thing to do.

Safety first when it comes to mains power and big capacitors.

That's a standard power cable. I have a dozen of them sitting around If it were an integrated power cable, then yes it would be a pain to open up the flash and replace the cable, but if you have one lying around (or can borrow one from a computer or guitar amp), then why not?

[lharby]

Thanks. I've already ordered replacement cables.

I've photographed the manual (just a plain photocopy) it's not super helpful, but I'll try and upload it later.

There is a company email address of fotobyte. I just googled them and the product shows up on Amazon although it's currently unavailable.

https://www.amazon.co.uk/Fotobyte-Photography-Studio-Portraiture-Product/dp/B00E8BU5DO

[lharby]

OK

Bit of an update.

I have a 3rd light which has never been used. Tested without the softbox, at close range I was getting f.22 at 100ASA 1/60th

The dial seems to make a difference but only 1 stop. However opening up the box for the 3rd strobe I found a small bulb inside, and it seems as though this will fit into the centre of the strobe. Although I couldn't get it to press in/didn't want to break it. Assuming that it fits, that will output a brighter flash I presume. There are central bulbs for the other strobes (in addition to the ring bulbs already installed).

I've put all the images into a google album here: https://photos.app.goo.gl/gzYzUe6u9NGeuUP67

Hope this makes sense. Maybe f.22 at 100ASA is the most I can expect from these.

[EarlJam]

I suspect that small halogen bulb is the modeling lamp. Take care in handling it, i.e. use cotton gloves, as the natural oil from your fingers will fry the glass and cause a failure due to heat when the lamp is on.

[Pete_R]

How are you checking the exposure? Do you have a separate flash meter? If so, are you using it in in reflected or incident mode?

Which model flash is it? The spec. in the picture is for three different ones. There's not a huge difference between them in power but if yours is the 120 then the exposure you're getting isn't too far off - more so if you have one of the others. It doesn't help that the GN has no details but you can probably assume it's in meters and with an ISO of 100. So, at 1 meter distance, you should need an aperture of f/32 if you have the 120 model - so not a huge difference from f/22 but it depends on what distance you were measuring from (you said 'close' so I'm assuming about 1 meter) but also depends on how you are using the meter etc.

Also note that the instructions say the first flash after you adjust the output will be at the previous setting so you need to fire the flash once after adjusting the output before using. Sounds like the adjustment is in the charge voltage of the capacitor so, once charged, it has to be discharged before the new setting is effective.

Given that the copyright notice you showed is for 2010 these aren't that old so I doubt there would be any degradation of the capacitors or the tubes unless they have been very heavily used.

[Francois]

Like Peter said. I doubt that the caps would age this fast (unless they are from a bad batch).
The light is a modeling light. It usually turns off during the exposure to avoid contaminating the light with a reddish glow.

Caps that go bad are usually pretty easy to spot. They will bulge and leak some cap juice that eats-up pretty much everything it touches. But that usually happens on the long run (except that time where a bunch of small contaminated caps made it onto computer motherboards https://en.wikipedia.org/wiki/Capacitor_plague)

[lharby]

Hi

How are you checking the exposure? Do you have a separate flash meter? If so, are you using it in in reflected or incident mode?

Yes separate flash meter. I was metering about 30cm away from the strobe, in incident mode with no softbox cover.

Which model flash is it? The spec. in the picture is for three different ones.

I *think* it is the p120, I will try and double check.

Also note that the instructions say the first flash after you adjust the output will be at the previous setting

Actually I did not know this, however I am pretty certain I took a few readings just to get a control.

Thank you for your input.

I might invest in brighter output units eventually.

[Francois]

If it's a still life in a somewhat darkened room to can always double pop the flash to gain an extra stop.

[Pete_R]

I was metering about 30cm away from the strobe, in incident mode with no softbox cover.

In that case, it does seem as if the output is low, but then again, without being sure how the guide number is calculated - who knows?

[EarlJam]

One thought - have you measured flash output at a distance of 1 meter? At 30cm, I wonder if much of the light is falling outside of the measurement zone.

[lharby]

One thought - have you measured flash output at a distance of 1 meter? At 30cm, I wonder if much of the light is falling outside of the measurement zone.

I will try this later hopefully and also making sure the existing values are discharged before measuring again. Thank you.