What lens you use for shooting your film really depends on what you are shooting. Is it an interview, action or something else. For the most part I like to stick to my 35mm 1.5 and my 55mm 1.5 lenses. I like to shoot with these lenses because they are very versatile. No matter the light, I can usually get the shot I am looking for.The background becomes soft while keeping the subject fairly crisp. However, when shooting with such a large aperture light tends to leak and can cause more fuzziness than is intended. Some highly expensive lenses can correct for this but in most cases it always happens. If you are shooting, say, an interview and you want the subject to be as crisp as possible a smaller aperture might be what is needed. What if you do not have enough lights? Well, then it becomes a little tricky, but you can overcome any obstacle if you have the right knowledge.
|Left is Sony 16-50 / Right is Tamron 70-200|
Here is a side by side comparison of two of my variable zoom lenses. The shot on the left is a Sony 16-50 2.3 constant aperture and the left is the Tamron 70-200 4.0 constant aperture. Arguably, the Sony is the better lens due to it being made in the same way the Zeiss version of this lens. The workmanship and the tolerances are the only difference. The Sony 16-50 is a great versatile, heavy lens that, at one time, was considered the best kit lens Sony had. The Tamron, on the other hand, is a good lens but it does tend to get a little fuzzy when out to 200mm. The color profiles are slightly dissimilar and the lighting is quite different. The left is lit with room lights and a soft-box, the right is lit with a soft-box and one 60 watt fill. As you can see, if you look closely, the subject on the left is fuzzy and is not as clear as the subject on the right. My focus was perfect, according to the Sony peaking meter anyway, so they should have been just as crisp, they obviously aren't. The reason for this disparity in focus is due to the aperture of the lens, or how much light it is letting in. The Tamron cannot go below an f4 but the Sony is at 2.3.
Needless to say, I will be using the Tamron for interviews from now on. That is, if I can get far enough away from the subject. You see, the drawback of using the 70mm is that I had to be more than 8 or 10 feet away from my subject. Something very hard to do in a 10 x 14 foot room. If that room I used the 70mm in was any smaller, I would have had no choice but to use the 35mm or the 16-50.
The other upside to using the 70mm is the fact that it has less inherent lens distortion than the 16-50 lens has. Because it has such a wide angle at 16mm, the lens tends to bend the shapes coming in the sensor. Good lenses will get most of it out but even then you have to zoom to about 25 or 35mm to get that distortion out of the picture. You could do it in post, but it is better to do it in camera, trust me on that one. A good 35mm or 55mm prime lens will have little to no distortion and you can trust that those lenses will perform just as good as the 70-200.
|An example of Bokeh|
So far you have heard me tout the goodness of the Tamron lens. It is a decent lens, for $400 you get every pennies worth. However, there is something this lens just isn't as good at as the 35mm and the 16-50. This is something called Bokeh. This is when the background has become blurred out of focus to the point that the only thing that is left is a round blur or shape. It is a highly sought out effect that makes beautiful shots that much more beautiful. It is possible to get some bokeh out of the Tamron but nothing like the lower aperture lenses. It is a must if you want to utilize an artistic focus pull on some close in objects. This would not be highly recommended to use on a dialogue heavy scene between two characters, best use the 70 for that. But, you know, it's your movie, If that's what you want to do. Go ahead!
So, which lens is right for your shot, well... Landscapes you need to use an aperture of about f 14 during the day and maybe a little lower at night. Interviews you want to get that aperture number as low as you can and still keep the subject sharp (move them further away from the wall would help loads btw) For action scenes during the day, you should use a smaller aperture (a higher number) to make sure the subject is clear, at night use the largest aperture (a smaller number) as you can without increasing that ISO too much. Dramatic scenes are great for using a softer focus so it might call for an f 1.5 aperture number (Larger aperture) instead of making it so clear you can see the pours on the actors faces. I mean, its supposed to be slightly dreamy this thing called love.. Isn't it?