Is a 300mm @21mp same as a 600mm@10mp?

Started Nov 14, 2008 | Discussions thread
LeonXTR Contributing Member • Posts: 820
Re: Is a 300mm @21mp same as a 600mm@10mp?

The reason I ask is I have a 1D MK III and a 300mm f/2.8 IS lens. IF
I were to switch to say a 1Ds MK III at 21MP is it ABOUT equal to a
using a 500-600mm Lens on my 10mp 1D MK III?

the greater pixel density of the 1Ds3 would be roughly equivalent to
a 340mm lens so well short of what you are looking for.

actually it would be a 450mm lens

No, the linear pixel density of the 1Ds3 is 15% higher than that of
the 1D3 which translates to a 300mm lens being effectively a 340mm
lens (probably closer to 345mm) when you crop the 1Ds3 to the same
pixel density. Where on Earth are you getting a 50% higher pixel
density from?


10mp vs 21mp = (almost)100% more pixels = (almost)50%more pixels on each side of the sensor

1DIII: 3888 x 2592
1DsIII: 5616 x 3744

3888 X 150% =5832(1DsIII 5616),like i said,almost 50% more
2592 X 150% =3888(1DsIII 3744),like i said,almost 50% more

Next time don't post rubbish when you don't even bother to do the math.

I find that shooting small birds/animals I have to REALLY crop to get
anything worthwhile. I know a longer focal length would solve the
problem but would more MP do the same thing?

As mentioned above you would need a much higher pixel density and
probably the only Canon DSLR that would give you the required density
is the 50D.

Which is by far the WORST decision you can make(trade a 1DIII for a 50D)

Not if you don't plan to buy massive lenses for something like
birding although the 1D3 has plenty of other qualities that put it
above the 50D that should influence any decision.

You clearly don't have an idea what's the image quality of a 1DIII vs a 50D do you?

Other than the 1.3 crop factor what am I missing here?

Pixel density is the key rather than sensor size.


Actually it isn't. Increasing the pixel density allows you to
enlarge the image more thus giving some of the advantages of a longer
lens (up to a point).

Take a 6MP 1.6x crop sensor and tell me how much extra reach that
gives you versus the 1D3. The answer is zero because they have the
same pixel density and it's not giving you anything that you couldn't
achieve by cropping the 1D3 image because it isn't recording any more
detail in the centre of the image.

Then by that way of thinking a powershot G9 is the same like a 1DIII

P.S. I already have a 40D and it is not nearly as good as the MKIII
so I don't want to go the 1.6 route.

In a sense, you're not losing out by using a 1.6 crop sensor assuming
you are using the higher pixel density to simulate a longer lens
through cropping. The big advantage of the 1D3 or 1Ds3 compared to
the smaller DSLRs is the added sensor size but a 22x15mm crop of the
larger sensor will be comparable to the performance of the small
sensor but without the resolving power.

You are forgetting the image quality parameter(a shot from 50D will
be unbelievably softer than one from 1DIII)

The difference will be far less than you think with any good lens.
People who have conducted proper tests on the 50D have shown it gives
almost exactly the gain in measured resolution that you would expect
from the increase in pixel density.

If you're photographing small objects such as birds where you can't
fill the frame, the 50D's extra resolution will pay dividends over
the 1D3 when you are limited by the focal length of your available
lens. The advantage of the 1D3's larger sensor counts for absolutely
nothing in these circumstances.

dpreview's test was done with an extremely sharp lens(50mmf1.4 usm) and the 50d does NOT give the sharpness you would expect from 15mp,it is much softer than the 12.7mp 5d WHICH WAS TESTED WITH THE SAME LENS

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