Shallow Depth of Field

I am interested in buying a canon rebel t3i with the intention of using it for digital video. The only dilemma I have is which lens to purchase.

I want to be able to have shallow depth of field and from what I have read, a large aperture will help achieve this.

The kit lens that comes with the t3i has a maximum aperture of 3.5. I looked into other lenses with larger max apertures but the ones in my price range are all prime lenses. Although I will probably not require zoom for my needs, it may be have a nice tool to have.

So, my question is, will the kit lens have a low enough f stop in order to achieve shallow DOF or will I need to purchase a prime lens with lower f stop? Thank you for all help!

If you're doing video, I'd suggest getting some old manual primes. Much better manual focusing, cheap, and it will give you as little DoF as you'll want. I love my Takumars.

I dont think the kit lens will cut it. If you are on a tight budget, check the canon 50mm f1.8. It will give you the shallow DoF you are after but if you want a smooth manual focus ring, you might be better off putting a bit more money for a 50mm f1.4. There's also the 85mm f1.8 that is perfect for that too.

Here few options:
Canon EF 50mm f/1.8 II
Canon EF 50mm f/1.4 USM
Rokinon 85mm F1.4 Aspherical Lens
Canon EF 85mm f/1.8 USM

Double post

First I suggest that you go to www.dofmaster.com/dofj​s.html and plugging in your numbers.
Shooting wide- like at 18mm- is going to result in a not so narrow DOF as compared to shooting long. Aperture has some to do with it- but NOT so much as most believe. You get better effect using longer lenses than you do short- and the aperture comes in a distant second. This is why it's harder to maintain focus at longer focal lengths in the first place- shooting wider gives you more DOF - easier to stay in focus.

So, the answer to your question is to get a longer lens over shorter- real wide is self defeating.

DOF with video on a DSLR works like DOF with photos on a DSLR- because we are using the same sensor.

Personally, if you are looking at video- you should be looking at the t4i with the 18-135 STM lens. The 18-135 STM lens is quiet- but I would suggest working it at the longer end.

Using the kit lens @ 18mm and f/3.5- at 10 feet- your DOF is about 21 feet. Wide is not a good solution for thinner DOF.

If you take 50mm at 1.8- @ 10 feet - your dof is 0.81ft. Using a f/2.8 zoom- 1.29 feet. @ f/5.6- 2.62 feet.

Using a longer lens - like a 85mm- at even a slightly longer distance- say 15 feet- gives you 0.63 feet @ f/1.8, 1 foot @ f/2.8 ( zoom ), 2.01 feet @ f5.6 ( kit lens) .

At the long end of the 18-135 kit lens- @ f/5.6 @ 15 feet- your dof is 0.79 feet.. Even at 25 feet- dof is still only 2.21 feet.

End result- more focal length is more important overall - IMO....

Just like photography, you need to consider your distance from the camera to the subject and from your subject to the background. In the end, a fast zoom is still better than the kit lens- but a zoom is still more versatile when it comes to framing and composition. Personally, I'd buy a kit lens - with longer focal lengths and consider fast primes only as a tertiary option- unless you are shooting primarily at one distance where the framing never changes. Upgrading the kit lens is like a double edge sword.. Faster lenses- more limited range & limited composition possibilities. For example, with what you want- limited DOF, I would not suggest going to a 17-55 f/2.8 for video- as you would probably be better off with a 24-70 f/2.8 instead- because longer focal lengths will help you accomplish the desired effects more easily.

If you decide to go with a prime- the older primes that are manual only- tend to have longer throws (more turn on the focus ring ) - making it easier to achieve critical focus.

Edit: after some additional thought- ideally- I'd get a 18-135 - mainly for the wide end ( where it does not matter ) and for the longer end, and maybe two primes- a 50mm and a 85mm. If the primes work for a shot- then use the longest one that works for the shot- otherwise your zoom would catch the extremes.

Mega Double Post Alert!!

Earwax69 wrote in post #14941077
Mega Double Post Alert!!

And the first being a rather unnecessary attack on the previous posters...

Hehehe, it's alright as he corrected it (or thought he did) before posting it.

If there is a lens you want more, you don't have to buy the kit. Just buy the body and the lens you want.

Thank you so much guys, that really helps a lot!