Least Noise - D3 Or D300 In Dx Mode

[Bill McCrystyn]

If the sensors are larger in the D3 then shouldn't they perform better (noise wise) as a result in the DX mode than the D300 with smaller sensors?

[James Shadle]

If the sensors are larger in the D3 then shouldn't they perform better (noise wise) as a result in the DX mode than the D300 with smaller sensors?

Yes, however you will only have a 6mp file from a D3 DX crop.
James

[Bill McCrystyn]

Thanks James. I just new there had to be a catch, but I didn't know what it was. No free lunch. Can you tell me how they cut it down? How they crop the frame.

[Leroy Laverman]

In DX mode the center portion of the sensor is used. This is really only for using DX lenses on the full frame D3 since these lenses were designed to produce smaller images on the focal plane. You can get the specific pixel dimensions here...
http://imaging.nikon.com/products/imaging/lineup/d3/img/downloads/D3_2p.pdf

[Bill McCrystyn]

Thanks Leroy. I hail from your area. I'm an old SLO town guy. Lived in Cayucos and Morro Bay for 23 years. I understood the Dx frame left the edges out and took the center but wondered how they shut down (rather than move the focal plane) the sensors to mimic a D300. If I understand you, you are saying neither happens, but instead, the Dx lens cast a smaller image on the sensors to be recorded? If this is the case what happens with a standard lens in the DX mode on a D3?

[Leroy Laverman]

A standard lens in DX mode basically crops the image to a 5.1 MP image. There's really no reason at all to use a standard lens in DX mode as you end up throwing away parts of the image. It would be better to capture everything and then crop later. I've seen some confusion regarding this issue on other sites. The 'crop factor' is not a multiplication factor. On a DX format camera one gets 10-12 MP in a smaller space. This is achieved by using smaller sensor photosites. One trade off with a smaller photosite is an increase in noise. A full frame sensor can use larger photosites for better noise response. There's a lot of technical reasons why this is so but in the end it doesn't really matter to most of us. We just want low noise however it's achieved. When you switch to DX mode you only use the middle portion of the sensor which gives you an apparent magnification but at the cost of resolution. The only reason this mode is available at all is to use DX format lenses on a full frame camera body. Without this mode, a DX lens would show major vignetting and no image at all around all of the edges. Of course I'm speculating a bit here as I have no DX lenses or a full frame digital camera to actually test this. Maybe someone out there has this combination and can make the camera record the full from with a DX lens attached to show us the results.

[Bill McCrystyn]

Thanks again Leroy. I do understand the cropping factor and sensor size but the D3 Dx modus operandi does have me a little confused. By the way, that loss of resolution is in the cleanest part of the lens and the frame lost to the edges altogether, is in the worst. I don't see much damage to the cropped frame, in fact Dx frames have cleaner edges as the inferior 5mm outside edge of the lens either side is not recorded.

By the way - enjoyed your gallery. Reminds me of home.

[Leroy Laverman]

You're right Bill. You would be losing the outer edges which optically speaking are not the best part of a projected image. The disadvantage is that you go from a 12.1 MP image in FX mode to a 5.1 MP image in DX mode. This is unimportant unless you plan on making large prints (or cropping after the fact). I'm no expert by any stretch, but from my understanding you generally want around 150 dpi or greater in a print (one site claims 137 dpi is the magic number). In FX mode at 150 dpi that gives you a 28 inch wide print. In DX mode at 150 dpi you can only get an 18 inch wide print. On a D300 the same DX lens would give a 13.1 MP image that could result in a 28 inch wide print.

I suppose I'll just chug along with my D80 until it wears out and by then there will be a D9 and D900. Right now I'm saving pennies for longer/better glass in front. I don't have the budget to keep up with the camera body side of things. It'll be interesting to see this same discussion in five or six years. :)

[Jim Fenton]

IMHO, there is a good reason to shoot in DX crop mode and that's file size.

Now...on the Xs bodies I shot previously, the DX crop mode had 2 benefits...those being a higher frame rate and also smaller file sizes, which allowed for more images on the card.

On the D3, where speed isn't a whole lot diifferent in any of the frame sizes, file size would still remain benefical....even though the D3 does have two card slots, etc.

Also...in DX mode, if you're shooting something moving, you have a whole lot better AF sensor coverage within the given frame.

I always found it very easy to work with personally.