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-   -   Canon S5IS f/1.4 lens? (https://forums.steves-digicams.com/add-lenses-49/canon-s5is-f-1-4-lens-174011/)

MadeByMarzipan Jul 15, 2010 11:21 AM

Canon S5IS f/1.4 lens?
 
Although I've had my Canon S5IS for a couple years, this is the first time I've looked into adding other lenses. I need a lens that is good for portraits, that will bring my subject into sharp focus while blurring the background. I've done a little research, and I think that a 50 mm f/1.4 lens might give me the results I want? What are your opinions on that?

Also, I'm a little confused about how the additional lens will attach to my camera. Does this Digital Concepts Lens Adapter (http://www.amazon.com/Digital-Concep.../dp/B000FSILBM) serve the same function as a filter adapter, or vice versa?

Which accessories do I need to buy in order to take those background-blurred portrait shots? Thanks for your patience with me!

JimC Jul 15, 2010 11:40 AM

Sorry... it doesn't work that way.

Your Canon model has a very small sensor in comparison to the sensors used in a dSLR model. As a result, you can use a much shorter actual focal length lens to get the same angle of view (apparent magnification).

The actual focal length of the lens on your camera is only 6-72mm. You'll see it marked on the front of the lens.

It just gives you the same angle of view you get using a 36-432mm lens on a 35mm camera (because of the smaller sensor in your camera, you have a much narrower angle of view for a given actual focal length lens). See more about how Depth of Field works here (keeping in mind you need to use the actual focal length of the lens for calculations):

http://www.dofmaster.com/dofjs.html

The larger the sensor or film size, the shallower your depth of field for a given subject framing and aperture. The smaller the sensor or film size, the greater your depth of field for a given subject framing and aperture.

That's because you have to shoot with a much shorter actual focal length lens to get the same subject framing at a given focus distance, which increases depth of field (or shoot from much further away if you're using the same focal length lens to get the same subject framing, and shooting from further away also increases depth of field).

Even if you could remove your existing lens and mount another one (which you can't due to your camera's design) to give you a wider aperture (which is a ratio between the focal length of the lens and the diameter of the aperture iris), you'd still have a much greater depth of field due to the camera's sensor size for a given subject framing and aperture setting.

Basically, you'll have about 4 stops difference for DOF purposes with your camera, as compared to a dSLR with an APS-C size sensor. IOW, even if your camera had a lens with f/1.4 available (and there is no way to give it one via an adapter), you'd have about the same depth of field you'd get shooting at around f/5.6 with a dSLR using a much larger APS-C size sensor for a given subject framing (if your subject occupied the same percentage of the frame). You'd also have a much narrower angle of view for a given focal length. Shooting with a 50mm focal length lens on your camera would give you the same angle of view you'd have shooting with a 300mm lens on a 35mm camera, meaning you'd need to shoot from further away to fit someone into the frame (giving you more depth of field because you're shooting from further away to get the same subject framing).

Your best bet with your camera is to zoom in more so that your subject occupies a greater percentage of the frame, putting more distance between your subject and the background.

In other words, go for a tighter head shot versus a full length shot (as the larger your subject and the more of the frame it occupies, the harder it will be to get a blurred background).

Or, use an image editor to blur the background to help you simulate a shallow depth of field.

TCav Jul 15, 2010 11:42 AM

That lens, and lenses like it, are intended for dSLRs like the Canon T1i. With the S5, you're stuck with the lens you've got and whatever lenses you can screw onto it. You can play with your settings, but the shallow depth of field you want will be tough.

And that adapter lets you mount filters and auxiliary lenses to your camera. It can't be used to mount a dSLR lens onto your S5.

MadeByMarzipan Jul 15, 2010 6:04 PM

Thanks for the info!
 
Wow, it seems I was really confused... thanks so much to you experts for clearing it up before I spent a few hundred dollars! I'll admit that, being the novice I am, I didn't understand all of what you told me... except that, it won't work! Which is very, very good to know.

Thanks again for answering my question (even though you must have rolled your eyes at me)!

Marzipan

TCav Jul 15, 2010 7:27 PM

I'm just glad you asked and we answered before you spent some money! :)


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