Photographic film, both black & white and color will yield an acceptable image despite the fact that the exposure was not spot-on. In other words, all films have what is termed as “Exposure Latitude”. Slide films have the least tolerance whereas negative films are remarkable because they grant generous latitude. In fact, the popularity of negative film is due to the fact that these films are super forgiving.
Why is negative film so popular? When we shoot pictures, it is highly likely that the amount of exposure received by the film will miss the mark. For the most part, this is OK because nobody looks are the negatives and says, “Look at Aunt Sally, doesn’t she look magnificent”? Now the negative is merely a means to an end. The end is usually a positive print on paper or perhaps a positive image on the computer screen. In any event, we must transform the negative image into a positive image.
The compulsory deed of producing a positive image from the negative affords the opportunity to make enchantments. If the negative is under or over-exposed we can apply corrections. As a matter of fact, we can also enhance by altering the image contrast or composition. Our ability to mend the errors made during the picture taking session is practically boundless.
When it comes to exposure latitude, negative film can easily tolerate 3 f-stops over-exposure and 2-f-stops under exposure. Suppose your camera is loaded with 400 ISO film. The tolerable range whereby you need not worry if the film was exposed somewhere between 100 ISO and 1600 ISO. That’s the miracle of the negative positive process.
Now “push processing” is the deliberate over developing of film. We do this if we know in advance the film was underexposed in the camera. The opposite is called “pull processing”. If we know the film was overexposed, we shorten the developing time in an effort to compensate.
My advice is to develop the film normally unless you have reason to think the exposure error was most severe.