Microfilm-based long-term data storage is an emerging technology in the archiving sector. Its estimated lifetime of up to 500 years outperforms other storage media like CDs, DVDs, hard drives, or magnetic tapes and makes this technology especially suited for archiving of digital data. Previous work has shown that the grid space, i.e., the distance between the exposure points, is a crucial parameter for the storage capacity. This paper presents investigations on a set of fixed-length modulation codes that can be employed to decrease the grid space at the expense of additional redundancy. The main question we address is, whether the smaller grid spaces achieved through such a modulation code justify the additional redundancy with respect to the overall storage capacity. Therefore, simulations based on realistic system parameters are carried out. Surprisingly, it turns out that the use of the analyzed modulation codes is questionable or even not advisable for digital data storage on microfilm.