Does anyone know: is the CCD in the Fuji F20 identical to that in the F30?

Just curious: I already decided to buy the F20. The F30 offers ISO 3200 (the F20 does not) but that may be a difference in firmware, not in the sensor itself.

It seems to me to be perfectly logical (and honest) marketing to use the same sensor in the two cameras and to differentiate the two models in the firmware.

(I suppose the F20 could be the place where the less "hot" sensors go.)

One of the other answers (that, in typical fashion, I read after posting my question) stated that the sensors are the same.

You're right: it could be amplification. But it is also conceivable that the best-performing sensors go into the F30s and the rest into the f20's. I think at times Intel has done that with Pentium chips: the specific model number is determined by how well the chip can perform (but otherwise the chips are from the same manufacturing process and line.)


I still think the F20 is (and for me is going to be) an excellent camera.
The F20 has a lower-resolution display. Any notion why it is that the F30 has longer battery life?

It is possible that where a chip fails in the tests for a higher grade it still pass the tests for a lower grade.

About battery life, F20 uses NP70 which has a capacity of 1150 mAH wherea F30 comes with NP95 which has a capacity of 1800 mAH. It is not surprising that NP95 lasts longer.

No surprise at all.

Duh.

Some stuff I got off the web follows. It appears that if amplification is NECESSARY to boost the ISO from two identical sensors, then IT MUST, by definition, be increasing the noise. That begs the question 'How can the sensor in the F30 gain true 3200 ISO?' (with the added noise that presumably would violate the ISO standard above 1600). Fuji seems to want to have it both ways.


The International Organization for Standardization (ISO) has a performance-based ISO speed standard for digital cameras, just as they have for film. ISO Standard 12232:2006 ("Photography — Digital still cameras — Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index") defines ISO speed in terms of the amount of light needed to achieve a certain "quality" in the sense of a per-pixel signal-to-noise ratio.

However, this standard ISO speed "rating" for a digital camera is not necessarily very related to the ISO "setting" or "exposure index" used on the camera.

The image sensors in digital cameras can be adjusted, or can have their outputs adjusted, in sensitivity to function with metering at any given ISO setting. This is usually done by simply amplifying the output of the image sensor, which increases image noise, sometimes beyond the level that the ISO standard says is acceptable.

Just as in photographic film, greater sensitivity comes with some loss of image quality, though this is visible as noise rather than grain. The best digital cameras as of 2006 exhibit no perceptible noise at ISO 200 sensitivity, and some produce useable results up to ISO 3200.

For digital cameras, ISO is shorthand for the ISO 12232:1998 specification maintained by the International Organization for Standardization.

This standard specifies signal to noise ratio and brightness requirements (or saturation for cameras that are limited by well capacity) for a camera to earn a certain ISO rating. These ratings are intended to be similar to those of ISO 5800:1987, which specifies ratings for film. Thus, at a given f/stop, shutter speed, and ISO, both film and digital exposures should produce roughly the same brightness as output. Note that in practice this isn't always the case due to many factors including interpretation of the standard, different tone curves, rounding, and marketing considerations.

As with traditional film ISO ratings, increasing the ISO corresponds to an increase in sensitivity. For example, in moving from ISO 100 to ISO 200, while keeping the f/stop constant, you will achieve the same exposure by using a shutter speed twice as fast.

In practice a single camera can achieve multiple different ISO ratings by applying some form of amplification to the signal coming off the sensor. This can be done by applying analog amplification to the signal before it hits the A/D converter, or by bit shifting the results after they have gone through the A/D converter. Cameras may apply a combination of these approaches, depending upon the desired ISO. Which is best will depend upon whether amplifier noise or A/D converter noise is larger.

Why do shots with boosted ISO have more noise?
Let's assume that we are keeping the EV constant, so the final output is the same brightness in a high ISO vs. a low ISO shot against which we are comparing. We'll also assume that we're doing analog amplification.

First, we'll consider the case where the ISO is boosted, but the shutter speed is kept constant, which implies that we have used a smaller f/stop. Since the integration time is constant, dark current accumulation will be the same in both cases, as will be readout noise and reset noise. Since less light was striking the sensor during the exposure, photon shot noise will be lower in absolute terms - since it is proportional to the square root of the signal and the signal is lower. However, the signal to noise ratio (SNR) will be worse overall since other noise source have remained constant, or shrunk more slowly than the signal. When this signal is fed through the amplifier, this has the effect of multiplying both the signal and noise by a constant. Since the SNR was worse than in the low ISO case to begin with, it will remain worse after amplification and get worse still with the addition of amplifier noise.

As a slight complication, we can consider the case where we keep the f/stop constant and use a faster shutter speed to compensate for the increased ISO. The analysis is basically the same as above with one difference: Dark current noise can actually decrease, which can give a slight improvement in SNR. In practice this effect will often be overwhelmed by the other factors decreasing SNR. The only case where it might make a difference would be for very long exposures with sensors that are prone to high dark current accumulation. (Astrophotography with crude CMOS sensors might be such a case.)