Can I get this kind of DOF out of the 35mm 1.8 DX???

Started 6 months ago | Discussions thread
slimandy
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Re: Here is what you need to know
In reply to primeshooter, 6 months ago

primeshooter wrote:

slimandy wrote:

That's not quite true. If you use a longer lens but you want the same framing you will stand back more and the resulting DoF will be about the same. However, the narrower FOV will give you more BG blur.

Example,

lets say you used the 35mm f1.8 wide open then used the 85mm f1.8 wide open but framed the subject in the same way....

35mm @ f1.8 from 3.5 feet..... DOF is 0.21 feet.

85mm @ f1.8 from 8.5 feet.... DOF is 0.21 feet.

So both lenses give you the same DoF and both are shallow enough for a blurred BG. The difference is the longer lens gives a narrower FOV so the BG is blurred more.

--
www.andrewsandersphotography.co.uk

Sorry? I said using a long lens gives more out of focus elements compared to a short lens which is true. OBVIOUSLY if you change the framing when you compare a short and long lens then it will change this! Just like if you changed aperture when you compare it's not really a fair comparison, eh?

I also explained getting closer gives more isolation...I explained through various points what affects dof, if you change variables when comparing then come out with a blanket statement that both lenses above give the same dof in your described situation- whilst not untrue, it's not comparing like for like and certainly doesn't change the fact that long telephoto lens can isolate subjects much better.

What you said was......

"Lastly focal length, the longer it is the more you can isolate a subject and have decreased dof.

With all this in mind, you'd be better buying a 50 or 85mm 1.8 or 1.4"

... and I have shown this isn't accurate. If you frame the shot like the example given by the OP your DoF will be the same. My figures for DoF we from DOF Master.

--
www.andrewsandersphotography.co.uk

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