Meter to set light intensity/time of enlarger for exposing BTZS test film???

[bobbysandstrom]

Is there a fairly inexpensive meter that will allow me to set my enlarger light intensity/time so I know that when I'm exposing my step wedge to film (for BTZS tests) I know I'm hitting it with the correct amount of light?

Thanks

 

[donbga]

Is there a fairly inexpensive meter that will allow me to set my enlarger light intensity/time so I know that when I'm exposing my step wedge to film (for BTZS tests) I know I'm hitting it with the correct amount of light?

Thanks

Any incident meter that can measure in EVs will work. You can get Luna Pros and the like of e-bay very cheap these days. You can use a reflection meter too but I can't recall the target EV. Ask Phil Davis on BTZS.ORG.

Don Bryant

 

[KenM]

You can also guesstimate the correct exposure. Use the manufacturers recommended film speed and developing time, and make an exposure. If, when you develop the film, you have a few clear steps on the developed wedge, followed by a gradual increase in density, you're close enough to do your tests.

If you've missed the exposure by too much, adjust, and try again. You don't have to be perfect for the film curve exposures, since all your measurements are graphed relative to each other, and if you miss a few steps on either end of the film, no worries, since there's lots of info there. Only as a last step do you determine your 'normal' film speed, which in turn drives out all the other film speeds and developing times.

I've been doing a similar test with Tri-X, although I have some questions around how to measure the gradient of tri-x in hc110, since it has an upswept curve, which skews the gradient measurements. I'll probably be heading over to visit Phil

 

[chiller]

Is there a fairly inexpensive meter that will allow me to set my enlarger light intensity/time so I know that when I'm exposing my step wedge to film (for BTZS tests) I know I'm hitting it with the correct amount of light?

Thanks

Have you done the psp test recommended by Phil Davis?

If not go to www.btzs.org and there is a good explaination in the articles section.

 

[donbga]

Have you done the psp test recommended by Phil Davis?

If not go to www.btzs.org and there is a good explaination in the articles section.

Exactly right Steve, but to get started the enlarger light intensity needs to be set intially to about an EV of 3 or 4 using an incident light meter. Normally this means you set the film EI value to 100 to arrive at the proper EV reading.

Don Bryant

 

[Lee L]

Exactly right Steve, but to get started the enlarger light intensity needs to be set intially to about an EV of 3 or 4 using an incident light meter. Normally this means you set the film EI value to 100 to arrive at the proper EV reading.

Don Bryant

Don,

Just checked on the article, and have a correction. The test requires that you set light level under the enlarger to EV 4.0 when reading reflected light spot metered off a white card in the film position, then expose the initial test for 1/2 second with 100ASA film. (http://btzs.org/Articles/PSP.htm)

I realize that you were probably working from memory, but just wanted to post a correction for readers who haven't or won't see the post at btzs.

Lee

 

[donbga]

Don,

Just checked on the article, and have a correction. The test requires that you set light level under the enlarger to EV 4.0 when reading reflected light spot metered off a white card in the film position, then expose the initial test for 1/2 second with 100ASA film. (http://btzs.org/Articles/PSP.htm)

I realize that you were probably working from memory, but just wanted to post a correction for readers who haven't or won't see the post at btzs.

Lee

Thanks, Lee. I should have checked the article before posting.

Don

 

[JHannon]

I have been using the Minolta IVF with the flat diffuser. Not a cheap meter, but you can do flash + incident and uses a single AA battery ($149 at KEH)

 

[bobbysandstrom]

right guys. I've done that, and, set the card to read ev 3 2/3 for fp4 (125). However, that's no guarantee to get you the psp of 2.4 hence the request for a light intensity/time meter. I asked Phil about this and he said I believe delta 100 is a true 100 and in D76 1:1 should produce 2.4 and if not adjust exposure. I wanted to avoid the hasstle of doing all that testing to find the psp. Thanks for your replies.

bob

 

[donbga]

right guys. I've done that, and, set the card to read ev 3 2/3 for fp4 (125). However, that's no guarantee to get you the psp of 2.4 hence the request for a light intensity/time meter. I asked Phil about this and he said I believe delta 100 is a true 100 and in D76 1:1 should produce 2.4 and if not adjust exposure. I wanted to avoid the hasstle of doing all that testing to find the psp. Thanks for your replies.

bob

Bob,

I would reccomend that you perform the PSP testing as outlined in Phil's article. One of the things it demonstrated to me is that I was over agitating my film.

Best of luck,

Don Bryant

 

[donbga]

I have been using the Minolta IVF with the flat diffuser. Not a cheap meter, but you can do flash + incident and uses a single AA battery ($149 at KEH)

Wow, that's a great price! I have the III and paid much more.

Don Bryant