Using Development to Cover Exposure Error

[Mike H.]

So, in calculating exposure for a negative I accidently make a mistake and shoot at f/30 something that should have been f/32. In addition, its a four zone scene so I would normally develop for N+1. Can I compensate with the developing time to make up for having exposed with too much light? If my N+1 is normally 12 minutes and normal is 8 1/2 minutes, would dropping the 12 minutes down to 8 1/2 to 10 make up for it? Without messing up totally the target number of five zones? I get myself majorly confused when I try to wrap my brain around that one. Any thoughts or explanations that someone could drop on me? Easy to understand ones would help.

Also, what if I made the same mistake in reverse? Shot f/22 when it should have been f/16 1/3. And in this case, the zones metered were six so I was planning on developing with a N-1, or 7 1/4 minutes. Can I do the opposite and develop somewhere around 8 1/2 to 7 3/4 minutes?

Thanks for any help you can give me.

[brook]

There could be more play in your shutter than the miscalculation you are worried about. I bet it will be fine.

[Daniel Geiger]

Hi Mike,

the easiest is, if you are off by <1/3 of an f-stop, don't worry, just develop normal. As brook pointed out, there is more variation in all the other factors (metering accuracy, shutter accuracy, developer concentration, developer temperature, etc) so that it does not matter. The difference between f/30 and f/32 is smaller than 1/3 of an f/stop.

With 2/3 off, you may consider adjusting, or just ignore it. I mostly do color (which usually is more fickle with exposure), and I do nominal exposure and +/- 2/3 f/stop (three sheets per scene). Often enough, two exposures are equally valid, just differ a bit in mood. With B&W you have more latitude in general, so 2/3 f-stop off, the film should easily bear. You certainly could develop a bit longer, which also will affect your gamma = steepness of the curve = contrast, though not much for a deviation of only 2/3 f-stop. Then you may also have to modify your temperature. Have a look at your developer temperature/gamma diagrams and chose the right combination. If all that sounds too complicated, I'd just develop as usual and adjust your printing times and filtration/paper grade. No biggie. If you scan, even less of a worry. Just adjust the scanner histogram, scan 16 bit, and all is good.

Once you are off by one f/stop or more, then you should go in and modify your development.

[Mike H.]

Brook and Daniel, Thanks for the comments and help. Makes me feel a little more comfortable.

[John Curran]

Also, what if I made the same mistake in reverse? Shot f/22 when it should have been f/16 1/3. And in this case, the zones metered were six so I was planning on developing with a N-1, or 7 1/4 minutes. Can I do the opposite and develop somewhere around 8 1/2 to 7 3/4 minutes?

Thanks for any help you can give me.

Yes you can compensate for under exposure by over developing, however you may experience a slight loss of highlight detail. Also you will need to increase development by 20-30%. Based on a base time of 7 1/4, you would need to increase time to 8 3/4 or 9 3/4 minutes. Or you could simply rate your film 1 stop higher (eg. ISO 400 to ISO 800) and develop at the recommended time for the higher film speed.

John Curran