Pixel Pitch

With Nikon's new D3X coming on board I've read the term "pixel pitch" with regards to lenes suited for the bigger sensor.

I presume the light gathered from a large lens is focused on the sensor at varying angles depending on if the light is coming from the len's edge or the center. I presume someone has tilted some pixels to allow light to stimulate it directly rather than at an angle???

I would like a brief explanation, or a website, to understand this term. Or maybe it has been explained already??? Directions to that thread??

And does this term have to do with FX and DX lenses? Regular 35 mm photo lenes can function as FX for the D3. Will they work with the DX3 with the larger sensor?

Thanks, the fisch

Larry - A few answers :

-- "Pitch" in this case has nothing to do with leaning or tilting. It simply refers to the periodicity of the pixels. For instance, if there is a pixel every ten microns, then the "pitch" is 10 um. Note that this is slightly different than pixel size, which could be equal to the pitch, but is usually slightly smaller. Sometimes they are used interchangably though.

-- It would be difficult to impossible (and expensive) to tilt the photosites so that they collect light better, due to limitations in semiconductor manufacturing. Instead, microlenses usually exist over each pixel to help focus the light being gathered down into the pixel.

-- The sensor in the D3X (and 1Ds series, and 5D series, and D3, and D700) are the same size (or very close) to a frame of 35 mm film. So the lenses behave exactly as they would with film, from a coverage point of view.

Very informative. Thank you very much, David.

There was some discussion on another site, if I understood correctly, that the sensor in the D3X might be larger and the 35mm lenses would not work well (soft at edges) and that another generation of lenses might be needed. I must have misunderstood.

Here is a question from another site mentioning the difference in lenses. This same thread talked about pixel pitch.

> Was this lens designed for the Dx format only?

No, it was presumably designed for 35mm film cameras and digital DX cameras, since there were no FX digital cameras at the time of development or release of the 70-200 lens. A FX digital camera requires better/different lenses than 35mm film did.

Any comments, David?

David or anyone else who wishes to chime in....

And another post from the same site which I quoted above and it mentions changing the microlens, "offset". Is that "pixel pitch"????

Thanks again. the fisch



>>> A FX digital camera requires better/different lenses than 35mm film did.
>
> Bob - can you elaborate on this? I wasn't aware there is an FX-specific
> format or higher technical spec. I have the zeiss lenses and as far as I
> know they aren't "FX" but they are 35mm film. I am not sure I understand
> what would be the difference between the two

It's not something I know much about, but I've read that sensors only get optimum quality if the light rays hit at rightangles, otherwise you get scattering of light through the microlenses. Whereas the angle of light has little effect on film.

It's most obvious on rangefinders - the lens is so close the sensor that the rays for the corner of the frame come out at sharp angles, causing vignetting (and maybe softness?) at the corners. Leica had to offset the microlenses in the M8, possibly to get round this, and that isn't even 35mm format

Larry -

The D3X sensor is 35.9 mm x 24 mm. 35mm film is 36 mm x 24 mm. Pretty darn close.

I've heard it mentioned before that digital somehow requires different lenses. While it may be true that there is some small amount of optimization that can be done based on a digital sensor, the millions of people using 35mm-designed lenses on digital (including pros and fine art types who get phenomenal corner to corner results) seem to prove that you don't need digital specific lenses. There are telecentric lenses (all Olympus four-thirds lenses, for instance) that are designed to create more light perpendicular to the sensor. This may be one reason they are highly regarded, but it's not like high end Canon or Nikon lenses aren't well regarded. Just ask all those pros using older Nikon lenses on their D3's.

As for the micro-lenses, the offset is the way the focus points of the individual lenses are shifted relative to the pixels to make up for the angle of incidence of the light. I don't know a whole lot about them, except that they are a help to getting light that hits the pixel at angles to actually reach the pixel sensor. They get shifted or offset more in the corners to help overcome the problem with light hitting at large angles. As you mentioned, this is exacerbated by having a lens aperture closer to the sensor as with the M8, or having a wider field of view, and can lead to softening or vignetting in the corners. (I think this was partly true for film as well though, but I've never shot film. And lenses are almost never as good in the corners as the center, no matter what medium you're talking about.) I'm not sure where the limits are of the ability of the micro lenses to correct for this.

I'm constantly amazed at the quality of reproduction with digital, esp. in good light.

So, getting into stuff like pixel pitch is interesting but not practical. I should probably be outdoors now snapping away rather than reading, eh?

I have several old Nikon lenses.

My D300 was ordered with the 18-200 DX VR.

I'm going to use some of the old lenses and check them out. The "sweet spot" might be larger for the smaller D300 sensor. I've got a 35 mm 2.8, 50 mm 1.4, 55 mm macro 3.5?, 135mm 2.8?, 35-105mm zoom, 80-200 zoom, and 100-300 zoom, and the 500 mm reflex (mirror).

All these are manual focus but that doesn't bother me.

For birds in flight and more action oriented shots I'll use the DX-VR lens for the fast focus.

Pixel pitch? From what you've indicated that should not make a noticable difference.

Thanks again for your time. the fisch

I wouldn't discount pixel pitch entirely Larry. In particular, larger pixels (and consequently larger pitch) generally make it easier for the camera to have good low light capability; That is, they'll be cleaner at high ISO, all else being equal. That's why the D3 will have better high ISO performance than the D3X for instance. (Of course, the "all else equal" only applies to similar generation cameras.)

There are also some effects in terms of diffraction and resolving power that are affected, but I do think most people tend to worry about that too much.