Slightly under/over developing

<p>I want to develop HP5 at 12:30 instead of 13 and ilford delta at 12:30 instead of 12. Is this okay? Will it leave little to no effect?</p>

<p>5% of 13 minutes is 39 seconds; 5% of 12 minutes is 36 seconds.<br>

A 5 % change in development time will have little noticeable effect on the negative.<br>

12:30 is -4% of 13; 12:30 is +4% of 12. The brightest highlights will be affected the most by the changes.</p>

<p>I was recently reading about T-Max developers:</p>

<p>http://imaging.kodakalaris.com/sites/prod/files/files/resources/j86.pdf</p>

<p>and noticed the recommendation for 20% decrease in development time for condenser enlargers. </p>

<p>Decreasing the time decreases the contrast, which is sometimes good. </p>

<p>For non-professional use, you don't have to be all that close, though you should still try to get the time appropriate for the temperature of your developer. </p>

<p>For professional use, consistency can be important. If you do trial rolls to determine exposure and contrast, you want the time to be close, such that you can repeat the same results.</p>

<p>By the way, tradition is to time from when you begin pouring one step, until you begin pouring the next. Leave about 15s for pour out time. </p>

<p>As for your actual question, it depends somewhat on the exposure. If you were stretching the exposure, in a low light situation, exposing at full aperture and slowest shutter speed that you can hand hold, you might go for a little extra time. If the exposure was in a high contrast situation, with both sunny highlights, and darker shadows in the frame, you might go for a slightly shorter time, especially with a little more exposure than usual.</p>

<p>At what speed are you rating your film...what developer are you using...<br>

12:30 sounds like a slight "pull" of the HP5, if you're using ID11 as your developer, (don't know which Delta you're referring to), and as Mr. Monday states, highlights will be affected most. If your exposure is a little under, say 1 or 2 thirds of a stop, you should still get very reasonable results, your contrast will increase a little, nothing wrong with that if that's what you're after. Most B/W films are very forgiving, and can tolerate a little in either direction whether it be exposure or development.</p>

<p>I think that small percentages in development times aren't too problematic, but when you start getting into the 10% range and above, that's where things start to show noticable differences.<br>

Key is, be consistent in your methods so that results are repeatable. Don't be afraid to experiment with exposures and development, that's how we've all learned. <br>

One other thing to consider...are you printing in a darkroom, or...do you intend to scan the negatives and then have them printed?<br>

Most of all...have fun with it!</p>

<p> </p>

<p>I presume the idea is to allow two rolls at the same time. </p>

<p>Depending on exposure conditions, you could go for both at 12m or 13m. Most often, a little more development is better than a little less.</p>