D700 in crop mode = > D40?

[Wigster]

Hey all, got some quotes from Jessops today for my D700 and 50mm 1.4, I'm very pleased.

I hate asking daft questions like this as I know they're out there somewhere on the internet, but anyway:

Am I right in thinking that the D700 (12.1MP) will outweight the "DX" crop factor positive of a higher affective focal length if you crop it to the D40's MP of 6.1mp?

(maybe that isn't very clear?) Basically.. will a 200mm lens on D700, cropped in to the D40 (DX) focal equivalent of 300mm in photoshop have the same IQ?

Also..
With regards to ISO equivalents, I understand the H1 modes, but how do the LO modes work, 200 is a native iso of the D700, but what actually happens when you "bump" it down to iso 100? does it just lower the brightness sort of thing?

 

[HoppyUK]

Hey all, got some quotes from Jessops today for my D700 and 50mm 1.4, I'm very pleased.

I hate asking daft questions like this as I know they're out there somewhere on the internet, but anyway:

Am I right in thinking that the D700 (12.1MP) will outweight the "DX" crop factor positive of a higher affective focal length if you crop it to the D40's MP of 6.1mp?

(maybe that isn't very clear?) Basically.. will a 200mm lens on D700, cropped in to the D40 (DX) focal equivalent of 300mm in photoshop have the same IQ?

Also..
With regards to ISO equivalents, I understand the H1 modes, but how do the LO modes work, 200 is a native iso of the D700, but what actually happens when you "bump" it down to iso 100? does it just lower the brightness sort of thing?

D700's full frame sensor is roughly 2.5x larger than the D40, so the maths doesn't quite add up to 6.1mp but you're on the right lines.

I don't use Nikon so don't know how the 'artificial' ISO works out in practise, but you will not get the expected increase in image quality that you might normally expect by lowering the ISO.

The lower ISO is there in case you need it and is not intended as a regular setting. You'll find all the answers here though in this test by DPReview http://www.dpreview.com/reviews/nikond700/

 

[chrisgeary]

According to dpreview's tests, lowering the ISO to 100 on a D700 reduces dynamic range, the highlights clip a little earlier. I haven't tested as I see no real need to.

 

[Nod]

In Dx mode, the D700 gives 5.1 MP (2,789 x 1,848 pixels) - less than the D40. So, if you crop to 6.1MP, the crop factor will be slightly less than the 1.5x usually quoted for the Dx sensors.

Both the Hi and Lo ISO settings are best avoided unless you really NEED to use them - to get longer exposures, use a ND or even a circ Pol rather than Lo.