Help with Decision for 5D Mark III

Noted Dan was asked and I am not answering for him – just stating facts:

As the sensor (or film size) increases, the POSSIBLE minimum DoF attainable with any given f/stop is decreased.

As a very simple example – if you take a picture of a person with a 50mm lens on a 5D and shoot at F/4 and then take EXACTLY the SAME framed picture with EXACTLY the SAME Perspective using a 7D (you would need about a 31mm lens): Then to get the SAME DoF, you would need to use F/2.5

The ‘difference’ between APS-C and 135 Formats (aka ‘Full Frame’) is close enough to 1⅓ Stops.

The most glaring example is the difficulty in making very shallow DoF images with a P&S or other smaller sensor, Sub Miniature Format Cameras.

These ‘differences’ created by the sensor or film size, are referred to as “EQUIVALENCE (in PHOTOGRAPHY)”.


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Addendum:


A more technical explanation

The 'Depth of Field' (DoF) is determined by:

The Focal Length of the Lens (FL)
The Shooting Distance - sometimes also referred to as the Subject Distance (SD)
The Aperture (Av)
The Circle of Confusion (CoC)

Now whilst the CoC has an history which is a muddy and based upon an arm's length 10x8 plate at worst and the "average" human eye's resolving power at best: there are accepted norms for the CoC.

These norms for the CoC VARY, with Film / Sensor size.

That's why, as the sensor size changes (as the CoC changes) the RANGE of DoF POSSIBLE also changes.

And the smaller the sensor, the smaller the Aperture which is required to achieve the SAME DoF for any given IDENTICAL shot.

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As a simple generalization: the 135 format camera range across all brands (aka ‘Full Frame Cameras) has the greatest range of fast lenses which are easily available and therefore affords the easiest and least expensive option for Photographers who require a very shallow DoF – I believe this is the point Dan K was making.

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This “Equivalence” is referred to in Scott Stephen’s post #14, where he compares the 24 to 105/4 to an F/2.8 zoom - here:

“It also makes up for the loss of a stop worth of shallowness in DOF on that f4 lens vs. an F2.8 lens. The f/4 on a FF will give as shallow or a bit shallower DOF as an f/2.8 does on a crop 1.6, as I understand it.”

And I respond to that comment in post #15 - here:
“PS Technical note:

The DoF “equivalence” between 135 Format and APS-C Format is about 1⅓stops.
So as an example for the comparison mentioned:
The DoF capacity for any given shot using 24 to 105F/4 lens on a 5D ≡ 15 to 65F/2.5 lens used on a 7D.”




WW

Quote:

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Originally Posted by William W

'morning . . . I was being politically correct to the lower order 'L disadvantaged' lenses . . . they have feelings too, you know.

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I can just imagine a trainee photographer attending their first nude shoot ...

"Wow - she's beautiful! Look at her curves - look at her shape! Lovely - just lovely - which L-lens is she again? Is it the new EF24-70 F2.8L USM II?"

Quote:

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Originally Posted by Polar01

Dan: you stated above that you geta better DOF with a Full feame, I really believe that is incorrect but instead is the lens that creates the DOF.

Cheers:

Allan

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Hi Allan,

Not better, but shallower, as William W noted. In a nutshell, you can compensate in either direction, as long as you have the leeway in aperture.

A very good post explaining this is an old one by Bob Atkins, here.

Dan

Quote:

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Originally Posted by Colin Southern

"Wow - she's beautiful! Look at her curves - look at her shape! Lovely - just lovely - which L-lens is she again? Is it the new EF24-70 F2.8L USM II?"

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I hear squealing during the night.
I have only recently discovered that it is my 16 to 35mkII complaining about being in the same camera cupboard as the 20D . . .
Sheesh! Talk about snobbery - it's now becoming difficult for me to mount the two of them together . . . and they used to produce such nice photos.

Maybe I should “upgrade” my camera – any recommendations ? ? ? . . .
I was thinking about "going Full Frame" . . .
I’d guess that question hasn’t been asked before . . .



To All: ‘aveagreatweegend

I'd suggest Nikon Bill - they produce much nicer photos - but so long as you process the files using NX2 on a Mac, and don't use a UV filter ;)

:)

A pretty good review of the 5D3.

http://blog.kareldonk.com/canon-eos-5d-mark-iii-review/

Quote:

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Originally Posted by Polar01

Dan: you stated above that you geta better DOF with a Full feame, I really believe that is incorrect but instead is the lens that creates the DOF.

Cheers:

Allan

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you are both right! How about that.

With a full frame a standard lens will be about 50mm and with a cropped camera will be about 32mm. The 50mm will have less DOF at the same settings.


When I responded was unaware there were plenty of responses on page 2 making this post redundant.

Thanks a lot for ur participation guys. I finally got my 5d mark5 with 24-105mm lens plus flash speedlite 600 ex. For sure I´m going to appear with more cuestions here :)