Question: I want to do a photo shoot using film, but due to not being able to see the shots I've taken I would first like to take a digital photo, then recreate it using film.

If I used the same focal length, ISO, aperture size and shutter speed, would the photo was taken digitally be exposed the same as the film photo? Maybe crop vs non crop sensor may affect things?

If not, what can I do to achieve similar levels of exposure (I don't just want to rely on the film cameras light meter all the time)?

Answer: 
In abstract theoretical terms, the exposure parameters — aperture, shutter speed, and ISO — are the same no matter the camera or lens. In an ideal sense, f/2.8 at ISO 100 and ¹⁄₁₀₀th of a second will give the same exposure in the result on any camera.

You specifically ask if the sensor size makes a difference. It doesn't, as covered at [Do the same camera settings lead to the same exposure across different sensor sizes?](https://photo.stackexchange.com/questions/7800/do-the-same-camera-settings-lead-to-the-same-exposure-across-different-sensor-si/7801#7801). Exposure is per unit area, not across the whole frame.

In *practical* terms, cameras just aren't that precise, and any of the values can vary by a significant fraction of a stop. Digital ISO, in particular, is prone to a lot of variation from brand to brand and camera model to camera model. And, as Michael notes, there are differences in film and digital, especially regarding long exposures.

For your use of preview for film photography, though, **this can work**. I'd recommend shooting a roll with your preferred film in different situations, carefully recording both the digital camera's values and the settings you used on the film camera. Once you've done that, go through and compare the results; from that, you should get a general sense of whether you need to estimate up or down from the digital camera's metering — and whether there are situations which are special cases.

(See [Am I wrong to judge my exposure using my smartphone?](https://photo.stackexchange.com/questions/97073/am-i-wrong-to-judge-my-exposure-using-my-smart) for more.)
A “good” exposure is defined as that that amount of light energy that produces an image with satisfactory tonalities and color characteristics. To allow repeated and duplicated results, the industry has standardized the ingredients of the exposure. 1. Scene brightness (Lux or Lumen level) as measured by photographic light meter system. 2. Sensitivity to light of film or digital sensor (ISO). 3. Shutter speed (accurate timing apparatus). 4. Capability of the lens to gather and transfer light (f-number).

Given the standardization there remain numerous pitfalls. The accuracy of brightness measurements are a variable based on the truthfulness of the instrument and the procedure performed by the user. The sensitivity of film is well regulated by the International Standards Organization, digital sensors only loosely follow these guidelines. Modern shutters are quite accurate, nevertheless there will be errors. The f-numbers are a ratio that equalizes all lenses, regardless of their dimensions. However this system is slightly flawed because the f-number does not take into account light absorption with the system. 

Nevertheless, you can count on a reasonable like rendering of the subject provided the cameras are set to the same equivalent exposure. The differences encountered are facts of life. No two pictures taken with different cameras will be exactly alike. The difference is likely minuscule however when we compare film and digital there will are dissimilarities inherent to between the various medias.