Printable View
I have been away from LF for about seven years. I have returned. I once had a pretty good grasp of BTSZ but my memory has faded away. Could someone give me their method for exposing the film to the step tab. I have all the BTSZ tubes and gear.
Any help would be greatly appreciated.
Jerry
Hi Jerry - read and then re read this article from the BTZS site as it is the starting point to customise your system for use with the BTZS system.
http://btzs.org/Articles/PSP.htm
I expose my step wedges in a contact frame under my enlarger. Always in the same baseboard position. Some people use a camera shutter to control the light reaching the contact frame while others use a digital timer. I use an RH design StopClock which is remarkably repeatable.
The following was my reply to a very productive thread started by Ken Lee.
"There is an expression about a committee designing a horse and ending up with a camel and so it seems from most people that have only read the BTZS book but never used the "system". BTZS is not the Zone system. It is similar but oh so superior in many ways. I find it refreshing that Ken is actually setting out with the intention of using the system as designed. I've used BTZS for about 7 years now and initially just reading the book was "challenging" to say the least, however when I put aside preconceived ideas and practices from my past things started to make sense. I forked out for all the software, a densitometer and the processing tubes. I had to learn the methodology, the terms and accept what I felt may have been short comings of the system as a whole. The short comings were more mine though due to trying to use the system in ways contrary to its designers intent.
If you choose to go BTZS with the lot then you will need to set up your darkroom with the ability to test your film according to the requirements of the system. No other test data or method will work - for BTZS. It is an integrated system.
The Plotter program requires a known standard and that [for me] was/is based on Delta 100 processed in D76. Phil Davis lists both Delta and Tmax 100 as reaching a genuine 100 iso.
The requirements for calibrating your own enlarger for your personal speed point may take an afternoon but is only done once. This calibration step accounts for your enlarger, timer, thermometer and agitation. You expose film in contact with a step wedge and read that into the plotter program. For the PSP test 3 sheets are exposed using an accurate repeatable digital [preferably] timer and then processed for 4, 8 and 16 minutes. The step wedges are then analysed by the plotter program to determine what your PSP is. If the PSP value you get from your set up matches the figure Phil has determined your testing standard has been established. If not the BTZS site has simple instructions to get it all set correctly. Once determined you will have an EV reading of your enlarger light source and a PSP number for the plotter program.
Once you have your PSP determined ---
The premise of BTZS is tying everything back to the media you are going to print on. About 2 hours testing of your paper will determine the actual grades of the paper and an "ES" value that will be used by the plotter program when you create an exported file for the Palm or the new iOS version of ExpoDev. Your paper testing must be done using the actual enlarger or light source you use for printing.
To test your actual film, set the EV of your enlarger to the one you determined with your initial test adjusted up or dawn to account now for the boxed speed of the film you are testing. EG if the 100 iso standard requires EV4 then a 200 iso box speed film will require the enlarger to be adjusted to EV3 for the series of step wedges.
Five sheets are exposed identically and then processed at 4, 5:40, 8, 11 and 16 minutes. You can if you wish increase the 16 minute time to 20 minutes if your developer is capable of sustained development to that time and that can sometimes give you a greater range from the film you are testing. D76 is one developer that can easily develop to that time without the resultant film curve becoming misshaped due to developer exhaustion. The results are read into the plotter and your testing is basically completed. The plotter analyses the wedges and sets the point of darkest texture and based on your tested ES value the brightest highlight with just visible texture. The plotter sets other important points of course including the speed that your film has tested at. From a very small amount of effort you now have a collection of data including the SBR [range] of your film. Times temperatures and film speeds. Zones and more. A file can now be exported to your mobile device with the ES applied for your paper grade you want to print on.
BTZS testing will very quickly show you what a film/developer combination can and cannot handle. BTZS testing will only give you useful data within what the film/developer combination can be expected to produce high quality easily printable negatives. If your light conditions in the field exceed your test results ExpoDev will tell you you have exceeded the capabilities of the film.
BTZS allows you to use either Incident or spot metering, I use both, and both work equally as well. Both can be used for "creative" placement of tones within the range of your tested film. Both have their own particular limitations in any type of photography but these are minor and once metering experience is gained with the system both work equally as well.
There appears to be a basic lack of understanding of what BTZS really is on this and other fora, BTZS is not the Zone system. It is similar but oh so superior in many ways. it is a complete system of testing exposure [factors, bellows, reciprocity and individual sheet development times]. The learning curve initially is a bit steep but it is soon forgotten and becomes an automatic part of your photographic arsenal. BTZS has bucket loads of info for the photo geek but if figures bore you then those figures will not even concern you as you take your first beautifully exposed and developed negative to your enlarger. Phil Davis was certainly a photo geek but he was also extremely practical and his wonderful system reflects that.
Steve "
I hope some of this gets you started,
Quote:
Originally Posted by Steve Nicholls
Thank you so much for your time. I very much appreciate your help.
If you have any further questions I can help you with PM me.
Also if anyone intends to eventually only use the ExpoDev side of the system Fred Newman at Viewcamerastore.com offers a complete film testing service for those with the new i[thing] app.
Steve
I use the same meter for checking the "EV" of the enlarger light as I do in the field. I think the BTZS book calls for a reflected reading off a white baseboard. I use the same incident meter in the darkroom and in the field and it seems to work.
I use the same meter in the field as well. A minolta incident.
With the incident meter - remove the dome and place it in the same position as the film/stepwedge will be with the exposed cell facing up to the enlarger lens and adjust the aperture for your first test to EV 4. Always measure from this same spot.
If you use a spot meter ideally the back of a Kodak grey card [pure white side] with a circle drawn so that you know where you are aiming the meter. Adjust the aperture for your first test to EV 4 read off the white card. It is important to meter from the same spot each time and allow your meter to adjust if it is not overly sensitive to lower EV levels.
For the spot reading any white card will do, you will adjust EV to get the 2.4 PSP. With both incident and spot metering the actual EV reading you end up with is not as important as arriving at a Delta 100, 3 sheet test that returns an iso triangle at or very close to a P[ersonal S[eed] P[oint] of 2.4 Speed point is not EV it is a factor built into the WinPlotter software that is adjustable between 2.2 and 2.6 Phil Davis recommended 2.4 as that put the film curve family in the "middle" of all the data obtained with the plotter.
Expose develop and read those sheets and based on your results in the WinPlotter follow these instructions.
http://btzs.org/Articles/PSP.htm
You don't need to be too A**L between 2.35 and 2.45 is pretty good. But you will -- no matter who you are try to get as close as you can to 2.4. I know I did :)