We present a critical assessment of commonly used pre-main-sequence isochrones by comparing their predictions to a set of well-calibrated colour-magnitude diagrams of the Pleiades in the wavelength range 0.4-2.5um. Our analysis shows that for temperatures less than 4000K, the models systematically overestimate the flux by a factor of 2 at 0.5um, though this decreases with wavelength, becoming negligible at 2.2um. In optical colours this will result in the ages for stars younger than 10Myr being underestimated by factors of between 2 and 3. We show that using observations of standard stars to transform the data into a standard system can introduce significant errors in the positioning of pre-main sequences in colour-magnitude diagrams. Therefore, we have compared the models to the data in the natural photometric system in which the observations were taken. Thus we have constructed and tested a model of the system responses for the Wide-Field Camera on the Isaac Newton Telescope. As a benchmark test for the development of pre-main-sequence models, we provide both our system responses and the Pleiades sequence.

Cone search capability for table J/MNRAS/424/3178/table2 (The full Pleiades photometric catalogue with colours and magnitudes in the natural INT/WFC photometric system (includes also table5) (24-Jan-2024 version))

Cone search capability for table J/MNRAS/424/3178/table4 (The transformed Stripe 82 standard star catalogue with colours and magnitudes in the natural INT/WFC photometric system)