Final answer:
The cracked appearance in photographs is usually due to incorrect temperature during development. Over or under-agitation affects contrast, and incorrect temperature during fixing causes other issues but not cracking. Sensitivity to chemicals can lead to allergic reactions or dermatitis.
Step-by-step explanation:
The processing error that causes a cracked appearance in photographs is most likely due to incorrect temperature during development (Option 4). A cracked appearance can occur when the developer's temperature is significantly different from the recommended range. It is essential to maintain proper temperature control to avoid damaging the photosensitive layer on the film or the paper, which can result in a cracked pattern on the final photographic print. Over-agitation or under-agitation of the developer solution (Options 1 and 2) primarily impacts the consistency of the developer's interaction with the film emulsion, affecting image density and contrast rather than leading to cracking. Incorrect temperature during fixing (Option 3) can cause other issues like reticulation or uneven fixing, but is less likely to cause cracking.
Photographers who develop a sensitivity to film developing chemicals and experience severe rashes on their hands are probably experiencing an allergic reaction or chemical sensitivity. This is a case where the immune system responds to a foreign substance, in this situation, chemicals used in film processing. Prolonged exposure or sensitization can lead to dermatitis or eczema, making it difficult to work with these chemicals without protective measures.