rodeo_joe1

19 minutes ago, ben_hutcherson said:

To add onto that...

Also... 

I totally agree that a "zoom" head makes a big difference when bouncing. The wider the better as far as quality of lighting goes - that's if softness and lack of hot spot reflections is the aim. 

So anything without a zoom reflector is quite limiting. 

26 minutes ago, ben_hutcherson said:

If one wants an era-appropriate flash

But, but, why would you? 

Things move on and (debatably) improve. That's why we no longer have to poison ourselves with chloroform or mercury fumes to get a photographic image. Or risk setting fire to things by burning magnesium powder for a flash exposure. 

On 9/30/2023 at 6:31 PM, hjoseph7 said:

The Gary Fong and the MagMod do not scatter the light in this manner, so they can also be used outdoors.

Errrm, they exactly do work by scattering the light and bouncing it back off any surrounding surfaces. Because the area of light they present to the subject is just not large enough to be classed as a soft source.

Diffusion alone does not soften a light source. The area of a small source like a flash has to be considerably increased to have a noticeable softening effect. This is lighting 101.

Check it out for yourself, outdoors at night, comparing the spread of shadow edges (the true test of light softness) using any kind of diffusing Dutch cap over your flash versus the bare direct flash. I think you'll find the only visible difference is a loss of one or more stops of light. 

In my tests you need about a 12" square softbox type diffuser (at portrait distances) to soften the shadow edges to any useful degree. 

On 9/16/2023 at 1:56 AM, dani_atao said:

When I turn my Canon Speedlite 199a on, the rising squeal starts.  But it never gets all the way to the normal high pitched level, and the flash never gets ready.

A classic symptom of a leaky storage capacitor. Maybe it can be re-formed with lengthy charging, maybe not.

Quite frankly, that old and underpowered 199a isn't really worth the trouble trying to revive. There are much better used Canon film-era dedicated flashes to be had for not much money. 

I see the 199a being offered on *Bay for 20 or 30 quid - and that's more than I'd personally pay for a 'remainder-bin' flash like that with a stated GN of 98 in feet - yeah right! That's (optimistically) <20 in meters @ 100 ISO in real life use. I also see Canon 540EZ flashes (1 stop more powerful) being offered for around the same price. While other brands of flash offer manual control and a wide range of auto-aperture control without being attached to a Canon camera.

What I'm suggesting is basically to save your time, frustration, wasted film or missed exposures and buy something a bit newer, more powerful and that's infinitely more convenient and useable. It'll need feeding with batteries less frequently, recycle a lot faster and almost certainly offer a wider range of convenient features.

And it doesn't have to cost much more either. 

I call BS on the whole pack of 'inexactitudes'. 

On 8/6/2023 at 4:16 PM, Ken Katz said:

Still, the main camera has a 71 sq mm sensor.. 

So, they've squeezed a 10*7mm sensor into a phone body about 6mm thick? That's some ray angle required from the lens! I'm surprised the corner vignetting doesn't fade to pitch black. 

And even if the sensor really is that size; that gives a pixel pitch of under 590nm. Needing a diffraction-limited f/1 lens to make any use whatsoever of the supposed pixel-density. 

Whatever. The sample pictures given at: 

https://www.tomsguide.com/features/samsung-galaxy-s23-ultra-tested-how-good-is-the-200mp-camera

All look like total crap to me. The JPEG compression and sharpening artefacts alone make any claim of a 200 Mp 'resolution' totally derisable.

Is there no regulatory body to prevent utter science-bending tr(hype) like this making its way to the public domain?

If they really could produce stuff like that - where's my time-travelling hover-scooter? 

It depends on the camera. Higher-priced models from pre-1950 nearly always had a genuine leather covering. Becoming less and less common as the C20th progressed, and being replaced by synthetics like vinyl, rigid plastic, paint, or that nasty rubberised-coating that goes sticky.

To answer the original question: The glue used for vinyl or leather coatings usually softens with white spirit - turpentine substitute. 

16 hours ago, probablypasta said:

How do i remove a post?

I don't think you can with this new site layout, but someone might need the information in future. 

4 hours ago, ben_hutcherson said:

... it charged to ~560V and fell to around ~430V in a minute. With both capacitors in the circuit(switch flipped to the "45" high power setting) I saw it charge to ~515V and it would drop to ~390V after a minute.

Wow! That's a high voltage, even for early 'electronic' flash, when H&S had a very low priority and flash tube technology was in its infancy. 

Many portable flashes of that era worked at just below 450 volts, which is/was a common maximum voltage for electrolytic capacitors. Hence the 440 volts delivered when it's mains powered. 

You might well be over driving the thing on 6 volts. That 4v marking probably means what it says. The fact that the peak voltage drops when both capacitors are in parallel could mean that the dielectric in one or both of them is breaking down and limiting the voltage.

If that's the case then the leakage current will naturally be higher than it should. You're also lucky that there hasn't been a loud bang followed by a shower of capacitor foil confetti! 

Is there no uF value and working voltage marked on the capacitor casings? 

17 hours ago, AlanKlein said:

So Joe, you're taking the square root of the sum of the squares of the f stops? 

Exactly, yes.

Works fine, since f-stops are based on the square root of lens area, and hence light-gathering power. Except the standard F-number series is inaccurate and highly rounded at every other stop. I.E. f/1.4 should be f/1.4142, f/2.8 should be f/2.8284, f/5.6 should be f/5.6569, etc.

Not an issue normally, but squaring those rounded numbers gives a larger discrepency when two or more of them are added. F/11, for example, should be SQRT(8^2+8^2) and not SQRT(121).

14 hours ago, AJG said:

Or just get a decent gated flash meter and skip the math.

Of course. That's what any sensible person would do practically. But that wasn't the OP's question - which was about ambient (presumably continuous) light addition. And working from logarithmic EV readings. 

The whole scenario is one that assumes individual light sources can be individually switched on/off and measured individually. When in most practical situations one would just stick an incident meter in front of the subject and take a single reading. 

Who the heck uses EVs anyway? Let alone converting the darn things to Lux. 

All you have to do is use a plain old light meter to get the F-stop readings at your chosen shutter speed for each light source. You then square each F-number, add them all up, then take the square root of the total as your working F-stop. 

Example A: Two light sources, one giving f/4 and another giving f/8 at the subject. 4 squared is 16, plus 8 squared is 64, giving 80 in total. The square root of 80 is 8.944272. So f/9 is your working aperture to the nearest 1/3rd stop. 

Example B: 3 light sources giving readings of f/11, f/6.3 and f/4.5. 

11^2 = 121, 6.3^2 = 39.69, 4.5^2 = 20.25. The total is 180.94 and its square root is 13.451394. Nearest preferred stop is then 13... or 14. Take your pick because both of them are only about 1/6th of a stop away from 'correct'.

A bit easier than converting everything to Lux or Foot-candles! 

Just remember that your working stop is always going to be a bigger number than your highest individual meter reading, as a double check on your calculations. 

To confirm: Here is a DSO trace of an SB-800 being fired in i-TTL mode. 

The shorter vertical line is the pre-flash and the taller line the main flash. 

The cursor function of the 'scope gives a time between the two of 60.4 ms with the camera shutter speed set at 1/200th s.

The delay may well vary slightly between flash/camera models and shutter settings; allowing for variations in mirror-lift time, etc. 

The above was with a D7200 camera.

FWIW. The sensor used to input the flash to the 'scope was a fast-acting photodiode with a measured rise/fall-time of less than 1 microsecond. The pre-flash itself has rise and fall times of over 48 and 21 us, respectively. 

On 8/17/2023 at 8:20 PM, ben_hutcherson said:

I also suspect that after 50+ years they may have lost some of their original oomph and if I get really brave I may try reforming them.

We'll, if you've charged them up enough to give a flash, then the job of re-forming is pretty much already done. 

You need to monitor the self-discharge leakage of the capacitor(s) to see how well any re-forming procedure is going. A quick'n'dirty way to do that is to see how long the ready-light stays lit after the charging circuit is switched off. Your lack of a neon ready-light obviously precludes that. 

Another way is to - carefully! - connect a high-impedance voltmeter across the capacitor terminals and watch how quickly the voltage drops after switching off the inverter. Good capacitors should only drop maybe 10% of their voltage per minute. Bad 'uns will drop to 90% in a matter of seconds. You will need to check there's no discharging 'safety' resistor wired across the capacitor though. 

I've only encountered a flash that stubbornly refused to re-forming once. That was a Sunpak Auto-Zoom 3600 that initially extinguished its ready light within a few seconds of switching the power off. After about 4 hours of mains-adapter powering and intermittent firing, that increased to some tens of seconds. After another 24 hours of continuous mains-adapter charging it kept its ready light on for about half the time of other examples of the same flash. Not too bad, but not good either. So IME, once those capacitors start to get leaky you might as well give up on them or replace them. 

(A good source of replacement flash capacitors are old 'rummage bin' cheap-name flashes like Hanimex or Cobra. The cappies in those are usually only 600uF @ 350 volts, but they're quite small in size and about 1/4 the volume of anything made in the 1950s to 1960s. 3 or 4 wired in parallel would give you a very respectable amount of flash energy.) 

I'm still around. Thanks to medical science. 

A mechanical self-interrupter (vibrator) was a common way to get an 'A.C.' supply to drive a transformer back in the early days of electronic flash. Quite inefficient; since it takes power to drive the contact-breaker solenoid, and can only work at a fairly low frequency. It gets the job done though. 

However, you could try bypassing the vibrator and juicing the thing up from a Nikon or Canon (or 3rd party) external HV supply - an SD-8 or similar. They're only an inverter in a plastic box after all. The voltage from those is about 340 volts, which should be enough, and they should easily fit in the space of a 4v lead-acid battery and vibrator solenoid. 

Incidentally, do you know the value of the capacitors? Any total value less than 1400uF is going to be less powerful than a hotshoe speedlight. Especially with a low efficiency bowl reflector that's probably a bit tarnished, and with no Fresnel condenser lens. 

P. S. I admire your bravery in powering up that thing at all. I would have worn thick rubber gloves, goggles and ear-defenders before applying any voltage at all to an ancient bit of kit like that. 

A bit late, but I have considerable experience with the Mamiya 645 system; owning 5 of the older metal-bodied versions (2x J, 2x 1000s and one 'M'). I've also owned some later plastic-bodied versions - the least said about them, the better. 

Anyway. Apart from the extra functions offered by the M (mirror-up and slow speeds to 8 seconds) and 1000s (1/1000th second top speed plus self-timer), there's very little difference in build quality and reliability between the 'budget' model J and the others. 

Having said that, extra functions always add extra things to go wrong. The self-timer will almost certainly get slow and sticky if not used regularly, and that 1/1000th top speed may not be too accurate or may give uneven exposure across the frame after years of use without servicing. 

Other faults that I've encountered - apart from gooey light seals of course - are (1) slow or sticky frame-counter zeroing when the back is opened, (2) delicate battery-door catches that easily break, and (3) poor contact between the body and a metering prism.

Those have been easily fixed by (3) cleaning the body contacts, (1) working the zero-return mechanism a few times and (2) sticking gaffer-tape across a broken battery door!

That's the sum total of trouble I've had with old metal Mami 645s, during decades of use. 

Turning to the lenses: In general the 'N' or 'S' versions are optically better than the original Sekors and IME the f/1.9 80mm is better than the f/2.8 version. 

The old, large diameter 45mm Sekor is to be avoided, and the 50mm f/4 shift lens is quite soft unless well stopped down. The 110mm N f/2.8 and 70mm leaf-shuttered lenses have a desirable image 'character' IMO, but finding a fully-working leaf-shuttered lens might be problematic these days.

That's about it. Those old metal Mamiya 645s are among the most reliable rollfilm cameras you'll ever find. Quality always holds its price. 

What kind of flare are we talking about? Well-defined streaks and blobs, or overall misting and loss of contrast? 

Streaks and blobs can be controlled by 1) a slight shift in angle 2) shading the lens better 3) flagging or using barn doors on the light source. (Any or all of the above might be useless if the light source is fully in frame.)

Overall misting and flare is a definite lens failing and needs a lens with better coatings or internal baffles. Sometimes stopping the lens down further will increase contrast considerably.

As to specific lens recommendations: Read published reviews, especially ones like 'Lenstips' that do a specific test for flaring. Individuals like us on PN rarely have enough experience of a wide range of lenses in one focal length to give a comparative recommendation.

For example, I've had excellent results from a Tokina 11-20mm f/2.8 zoom in Nikon DX fitting, but that doesn't really help with choosing an AF prime for Sony E-mount. And my current Sony gear is full-frame. Otherwise the 25mm f/2 Batis or Tamron 17-28mm zoom would get my vote for that sort of work. 

Vampire Jet speeding overhead

Stunt plane coming out of a Hammerhead Stall

RAF skydiver display team

Wingwalkers in close(!) formation. No montage trickery; the planes really were that scarily near to each other.

All pictures Sony A7Riv + Tamron SP 70-180 F/2.8 zoom.

When you say "missfires" do you mean fails to fire? Or fires randomly on its own? 

A failure to trigger is probably down to a faulty cable or connector - the non-locking DIN plugs used by Quantum are awful things infamous for sloppy connections. So check your synch cable or triggers and the cable between PSU and flash. 

Less likely is that the flash has an internal fault, like a dry-joint or failing trigger transformer. Check all your cables first. It's a lot easier and cheaper to fix than trying to diagnose a faulty flash unit. 

1 hour ago, JDMvW said:

In this context it has to be "froggie" think (see Blazing Saddles)

I was trying to avoid being that politically incorrect. 

13 hours ago, c_watson1 said:

Tanqueray and Bombay Sapphire bottles work nicely, too...

How do you get those over a speedlight, or put a macro subject inside them? 

Or do you just 'dispose' of the contents and not care? 

Besides, it seems a bit of a waste of money when you can't stand the taste of gin.

21 hours ago, Niels - NHSN said:

Kentmere 400 or AgfaPhoto APX 400 - whichever is cheaper as it is likely the same product.

I doubt that they're the same. The Kentmere brand name has been owned by Harman technologies for many years, while the Agfa photo brand is owned and distributed by Lupus imaging & media. 

Rumour has it that Agfa films are manufactured by Fuji. Fuji photo products also being part of the Lupus portfolio.

FWIW, film has always been expensive stuff, both in time and materials. One of, if not the main reason, why digital so quickly displaced it. 

Film made it far too easy to get anal over every step of the process. 

Telling people that a densitometer was an essential part of their kit is like saying to photographers today that they need a micrometer to make sure their SD card is the right thickness! 

14 hours ago, JDMvW said:

this used to bug the hell out of my French-speaking colleagues

Speaking of which, I remember seeing toy jumping frogs operated via a thin rubber tube and a pneumatic bulb. There were (are?) also pneumatic shutter remotes. So why not combine the two and say 'watch the frog' instead? 

12 minutes ago, Incongruent Phonon said:

And i got awfully bored.

Playing Sudoku, or taking actual photographs (good grief!) is much less destructive. 

Cheapest alternative would probably be a 15 year old camera like the Nikon Coolpix P5100. Now available for 50 or 60 quid, and  giving results like this - 

A one off payment that gets you a potentially infinite number of frames for next-to-nothing extra. 

You can boost the ISO to 3200 if you find the grain too fine for your liking. 

12 hours ago, c_watson1 said:

Diffusion adjustable

Indeed. I now choose my drinks based on how useful the container looks, not on what the contents taste like. 

Incidentally, a slightly more 'opal' drinks container made a great light tent for macro use. Just lay a flash next to it on low power and you have a directional but soft and 'enveloping' light for watches, jewelry, coins, etc. 

Personally I would measure the diameter of the remaining wire with a caliper or micrometer. But as a rough guide: You want something thin enough not to obscure too much light, but thick enough to handle the heat. Not too thick that it can't be easily bent and manipulated around the tube as well. 

I just put a digital caliper to the trigger wire of an old Bowens strobe tube, and it measures 0.31mm diameter (about 28 wire gauge). But the Bowen's strobe is rated much lower than 3000 Joules. 

I'd say anything between 28 gauge (0.32mm dia.) and 24 gauge (0.51mm dia.) would be suitable. With 24 gauge probably being a bit on the heavy and inflexible side for easy manipulation. Nickel wire being quite stiff and not too flexible.

So going in the middle with 26 gauge (0.4mm dia.) might be a good choice. It depends what you can lay your hands on.

P.S. The resistance is quite irrelevant in this application. The trigger wire carries almost no current, but at a very high voltage. The several Kv electrostatic trigger charge initiates ionisation in the gas of the tube, which then avalanches into a full scale plasma sustained by the main capacitor charge. The job of the trigger is over in a few microseconds at most. However the plasma in the tube emits a huge amount of heat, and it's this heat that the trigger wire has to withstand. 

I think the lessons to be learned here are twofold:

1) If it ain't bust don't fix it. 

2) Don't mess with a helicoid unless absolutely necessary. 

Not even a professional repairer takes a helicoid apart for the fun of it! Even if fully marked up and the alignment goes back together correctly, there's always a loss of grease in the process, together with the risk of 'grit' getting into the threads. Even normal house dust will degrade the smoothness of focus, let alone the danger of scratching or denting the fairly soft aluminium threads. The grease used is also a specialist product that has no common substitute. 

In short - leave helicoids severely alone! 

Also: A couple of specks of internal dust make absolutely no difference to a lens's image quality. And even if removed they'll probably be replaced with a couple more in a very short space of time.