Step wedge on film leaders

[Rich Ullsmith]

Dummy dum dum question, but why are there not step wedges exposed onto film leaders? I have numbers and arrows and bar codes, but not a step wedge. I would not expect it to be perfect, but it would be something.

For somebody like me who plays around with a lot of different films and developers, it would be instructive. Even if they were gauged to box speed, I think it would be better than the MDC. Is there a reason not to have a step wedge on frame #37?

 

[Kaboom]

I've no clue but it actually sounds like a pretty good idea...

 

[Marc .]

Rich,

This is a good idea.
If you can spare about three frames on a roll, do your own wedges !
Buy a used sensitometer on the bay, they are quite easy to find and cheap, and expose a wedge on the first frames.

You can also buy a used densitometer and measure the densities after development, and then you will be doing sensitometry.
Read Phil Davis' book : Beyond the zone system, it's all about sensitometry.

Marc

 

[Mike Wilde]

I tape a step wedge in a 120 roll film sized 6x6 test neg into the gate of a meduim format TLR once and a while to test out a new film. It is a bit of a hassle extracting it after the first exposure, but it can be done with access to a darkroom. I have also tacked a strip type step wedge against a piece of 4x5 film in a holder to calibrate a new film.

I usually just sacrifice about 8 frames from the first roll of a bulk load of 100' of film to calibrate the process, but bracket the exposures to get the vistrual analog to a step wedge.

 

[Photo Engineer]

You can actually print a step wedge onto a sheet of 8x10 and then photograph the step wedge at the front and end exposure of a roll of film. With some experimentation, you can plot this out knowing the densities on the print. It will also allow you to judge end to end process uniformity. The nice thing is that you can do this with any format.

PE

 

[Rich Ullsmith]

That makes sense to me, but . . . if you photograph your 8X10 printed wedge, then it must be critical that your middle gray is spot on 18%, right? That's the portion of your wedge you would want to meter, correct? Or would incident metering be sufficient? Or does it matter?

 

[Photo Engineer]

If you center the wedge with the proper exposure (dmin and dmax both are shown) then there should be no problem, as it is the mid scale straight line that you are after and what you will photograph.

You have to measure the print to know the separation of the steps so that you can plot everything properly, but it is a quick and dirty method to get a pretty reliable result. Don't worry about the 18% unless you are an ultra purist.

If so, it is best you include an 18% gray card instead, along side the wedge.

PE

 

[ic-racer]

My film has them....

(I put them there )