Head to head
Agfa APX 100 vs Agfa APX 400
Both are cheap, no-frills Agfa black and white films sold side by side, so the choice usually comes down to one number: speed. APX 100 gives you a slow, fine-grained ISO 100 stock; APX 400 trades some of that smoothness for two extra stops of light. That speed gap is the whole story, and almost everything else about how they handle follows from it.
How they differ
Shot in good light, APX 100 is the cleaner negative. Tighter grain, a touch more apparent sharpness, and smooth tonal transitions in skies and skin. It rewards a tripod or bright daylight because at box speed you are often working at slower shutter speeds. APX 400 looks grittier by comparison, with grain you can actually see at moderate enlargements, but that is the trade for being able to hand-hold indoors, shoot overcast streets, or freeze a little motion without pushing.
In practice the workflow difference is bigger than the look. APX 400 keeps you shooting when the light drops, where APX 100 would have you reaching for a faster lens or a tripod. Both develop in standard B&W chemistry with no surprises and both are priced at the budget end, so cost is rarely the deciding factor between the two. Availability and pricing for the 400 can be a little spottier depending on the run, but neither is a boutique film. If you like the high-contrast, slightly old-school Agfa rendering, you get it in both; the 100 just delivers it with more polish.
Choose Agfa APX 100
Pick APX 100 for daylight, landscapes, portraits with controlled light, and anything where you want the finest grain and smoothest tones this family offers. It is the better choice on a tripod, for slower deliberate shooting, and for big enlargements where grain would otherwise show. If your subjects sit still and the sun is out, this is the one.
Full Agfa APX 100 guide →Choose Agfa APX 400
Reach for APX 400 when light is the constraint: overcast days, shade, interiors, street work where you need a faster shutter, and anything moving. The two extra stops buy you flexibility that no amount of careful metering gets you from the 100. Accept slightly coarser grain in exchange for keeping the camera up and shooting in conditions that would stall the slower film.
Full Agfa APX 400 guide →The verdict
Neither is better; they cover different light. Buy APX 100 for bright, static, fine-grain work and APX 400 for low light and movement. If you can only stock one and your shooting is unpredictable, the 400 is the more forgiving everyday roll. If you mostly shoot in good light and care about grain, the 100 wins.