I'm going to try to write a straightforward answer to help photographers decide which films to choose.

Let's start with how photographic film works, and that is, very roughly, that silver halide crystals in the film emulsion are sensitive to light. It's these crystals that record the latent image, which gets turned into the final negative or positive image through the development process. Silver halide crystals are more-or-less randomly shaped.

Over the years, as research and development was put into improving photographic film, emulsion engineers developed a way of inducing the individual silver halide crystals to crystalise in a more regular, tabular form. This increased their surface area, making them more sensitive to light. The tabular crystals lie flatter on the film's surface, in a denser layout, reducing the scattering of light. Final images show increased resolution and reduced grain. Kodak named these new films using tabular crystals as T-grain emulsions.

The downside to T-grain emulsions is that they are not as forgiving when it comes to exposure latitude, they are less suitable for push/pull processing, and they're more sensitive to over-processing. If you are a beginner or you're working with a less-than-precise camera/meter, T-grain films can be harder to work with. Even when exposed correctly, some people find the final images too "clean" and "clinical" – lacking the character and grit often associated with traditional black and white photography.

As of 2025, Ilford is the manufacturer offering the widest variety of black and white films.

Ilford's DELTA PROFESSIONAL films are T-grain emulsions. The Delta line comprises:

• DELTA 100
• DELTA 400
• DELTA 3200

Ilford's PLUS films are not T-grain emulsions. They are more traditional, so-called cubic-grain emulsions. In this line, Ilford offers:

• PAN F PLUS (ISO 50)
• FP4 PLUS (ISO 125)
• HP5 PLUS (ISO 400)

Ilford also offers some other specialist emulsions – briefly:

• ORTHO PLUS (ISO 80 orthochromatic film – not sensitive to red light)
• SFX 200 (extended red sensitivity)
• XP2 SUPER (ISO 400 chromogenic B&W film, i.e. it does not get developed in the same way as other black & white film, rather it should go through the C-41 process)

Kodak has its T-MAX line of film – these are all T-grain emulsions:

• T-MAX 100
• T-MAX 400
• T-MAX P3200

Kodak also offers its seminal Tri-X film, which is a traditional emulsion not using T-grain technology. Tri-X is comparable to Ilford's HP5 PLUS.

In the past Kodak also offered Plus-X 125 which would have been comparable to Ilford's FP4 PLUS, but it's long discontinued. Kodak also used to offer C-41 B&W film, but that's also discontinued.