Re: X-ray Film example and comparison.
I have a rotary cutter for paper but was unable to use it for cutting a roll of aerographic film as it would have to be threaded from the wrong end under the plastic compression thing after every cut. A nightmare with floppy aero film. So I had to get a guillotine cutter for that, clearance on trademe about $30, it has a neat little arm that descends ahead of the blade and which holds the film still. If you use a rotary cutter its a good idea to tape a sheet of office paper around the plastic holder/compression thing to minimise potential scratching and to ease the paper in and out as it will hold the film down on the useable area.
Re: X-ray Film example and comparison.
Quote:
Originally Posted by
towolf
So, I got my first flash ever this week. It’s a studio flash that can put out f32 at 1 meter with a softbox attached.
I wanted to try it out and was pretty puzzled that my Sekonic readings for the relative power of the flash and my big continuous fluorescent lightbox did not seem to match at all.
Of course I did the tests with cheap Fuji x-ray film to start with and where I had equal power from two sides the flash side just didn’t register. It seemed to be something like 1.5 stops under.
So today, I did a 2x2 test matrix with Foma 100 and Fuji HR-E 30 with equal power and then 3:1 power according to my light meter. I rated the Fuji at EI 25 from my earlier stuff.
http://i.imgur.com/HzdU6gD.png
What was completely new to me that apparently there is reciprocity failure also at extremely short exposures? The flash barely shows on the x-ray film. Is this an effect of my rating it at EI 25? Is is off perhaps?
Or, could this be an effect of the double-sided emulsion?
I stripped the rear now and seems to look much more balanced:
http://i.imgur.com/rjzmZaQ.gif
Could the continuous light penetrate the base better and shine through to the other side, but the flash doesn’t?
This is front and rear respectively:
http://i.imgur.com/uBRJ31n.pnghttp://i.imgur.com/vwXZR6C.png
Re: X-ray Film example and comparison.
Quote:
Originally Posted by
salvatore
I use a guillotine cutter, and I am always afraid of hurting me when operating in the dark, and even under deep red light, since I must press the film quite near the cutting area..
I am considering the purchase of a rotary cutter, but I do not know if all cutters cut cleanly the Xray film, which seem to me quite strong.
Even my guillotine cuts only fairly; I must press the blade against the cutting edge to cut and not bend the film.
Does rotary cutter behave cleanly?
On my Premier Brand guillotine cutter, the gap, blade to cutting edge, can be adjusted. There is a nut that sets the spring tension to decrease the gap. Also, I use a drafting triangle placed over the paper / film to hold it tight. Seems to work for me.....
Re: X-ray Film example and comparison.
Quote:
Originally Posted by
towolf
So, I got my first flash ever this week. It’s a studio flash that can put out f32 at 1 meter with a softbox attached.
I wanted to try it out and was pretty puzzled that my Sekonic readings for the relative power of the flash and my big continuous fluorescent lightbox did not seem to match at all.
Of course I did the tests with cheap Fuji x-ray film to start with and where I had equal power from two sides the flash side just didn’t register. It seemed to be something like 1.5 stops under.
So today, I did a 2x2 test matrix with Foma 100 and Fuji HR-E 30 with equal power and then 3:1 power according to my light meter. I rated the Fuji at EI 25 from my earlier stuff.
http://i.imgur.com/HzdU6gD.png
What was completely new to me that apparently there is reciprocity failure also at extremely short exposures? The flash barely shows on the x-ray film. Is this an effect of my rating it at EI 25? Is is off perhaps?
Yes there is reciprocity departure when using extremely short exposures, but I doubt your flash durations are short enough to cause a problem. This occurs at 1/10,000 -1/5,000 second with most films
Re: X-ray Film example and comparison.
There seem to be three things it could be:
a) The flash output varies,
b) The settings were wrong,
c) The spectral output of the flash is not ideal for the x-ray film.
If it's an older strobe, has it sat unused for awhile? You may want to follow the manufacturer's suggestions for reforming the capacitors.
Take a number of readings over the space of a few minutes. Don't overhead the flash, and make sure to give plenty of time to recharge. Are they consistent?
If the spectral output is off, which seems unlikely, you might have to determine an EI for flash separately from your other sources.
Re: X-ray Film example and comparison.
Quote:
Originally Posted by
Peter J. De Smidt
There seem to be three things it could be:
a) The flash output varies,
I don’t think so, we tested Film A, Film B, Film A, Film B. We didn’t touch the flash in all this, we only changed shutter speed from 1/2 to 1/6 to unbalance the ratio between flash and hotlight.
Quote:
b) The settings were wrong,
I don’t think so, we designed the 2x2 experiment specifically to test film-vs-film and time-vs-time
http://i.imgur.com/LNJCxjs.png
Quote:
c) The spectral output of the flash is not ideal for the x-ray film.
It’s this one here. According to manufacturer it’s 5600 K.
Quote:
If it's an older strobe, has it sat unused for awhile? You may want to follow the manufacturer's suggestions for reforming the capacitors.
The guy said, he used it 2-3 times only. But it’s not super old.
Quote:
Take a number of readings over the space of a few minutes. Don't overhead the flash, and make sure to give plenty of time to recharge. Are they consistent?
If the spectral output is off, which seems unlikely, you might have to determine an EI for flash separately from your other sources.
I’m doing some repeated pops into the light-meter, and they are all bang-on f22. Will continue this.
Right now it must be compensated by roughly 1.5 stops. I can’t really believe it’s spectral. Why is everyone discounting the reciprocity failure theory?
Re: X-ray Film example and comparison.
Because your flash duration will not be short enough for reciprocity failure.
Re: X-ray Film example and comparison.
Quote:
When you use a flat bottomed tray for double sided film do you oscillate the tray during development? And if not, how does it develope in the side in contact with the glass?
Constant, gentle agitation for the first 30 seconds, followed by 5 seconds gentle agitation every minute. Agitation is north/south, east/west. Or if you're in Australia or New Zealand, south/north, west/east....;)
Re: X-ray Film example and comparison.
As Andrew says gentle agitation south north, west east. With my old film holders there's always a bit of a black line from light leakage, so I grab it in that wasted area and flip it over so both sides get the same amount of developer flow.
1 Attachment(s)
Re: Images shot on X-ray film
Attachment 141223
River Elbe Radebeul/Saxony
Pinhole f400 x-ray film 1:50 Rodinal
