Focal length 35mm equivalent, but not F-stop?

Started Jul 24, 2014 | Discussions thread
Great Bustard Forum Pro • Posts: 43,683
Re: Focal length 35mm equivalent, but not F-stop?

Tim Tucker wrote:

bobn2 wrote:

Beachcomber Joe wrote:

bobn2 wrote:

Beachcomber Joe wrote:

The total light will decrease but not the light per square mm of area. Since the amount of light falling on a specific area of the sensor remains the same the exposure remains the same. A lot of the technobabble you read hear is about total light. Total light can be ignored. What matters from a photographic standpoint is the amount of light per square mm hitting the sensor.

Completely wrong. What matters is the total number of photons captured. Differences in exposure can always be compensated by simply changing the relationship between exposure and output grey scale. The total light locks in a noise pattern in the image, which can't be altered apart from noise reduction, which will usually lose you image detail. Those wishing to maximise image quality deal in total light. Of course, if you stick to one sensor size, there is no difference between total light and exposure.

Some people may not have known what I meant by the term technobabble. Thank you for providing such an excellent example.

Technobabble it might be, but it is true technobabble, and you have no way of refuting it. So, when you 'Total light can be ignored. What matters from a photographic standpoint is the amount of light per square mm hitting the sensor.' you're still 100% wrong. Choose to call what you're incapable of understanding 'technobabble' if you like, it doesn't make you any less wrong.

I'm following this with interest, and learning some useful bits and bobs...

...such as how sensors work.

But I am a bit perplexed as to how "total light" and "highest image quality" relate to good image. In the 20th century film produced fantastic images, even early digital cameras produced fantastic images. In fact some of the images produced are still fantastic, so if you used the same cameras could you not produce fantastic images today?

Sure. But do you not agree that higher exposures for a given camera, no matter what camera you are using, result in higher IQ, all else equal, so long as you don't blow the highlights?

That's because more light fell on the sensor (film). The thing is, though, that the same exposure on different formats results in more light falling on the sensor (film) of the larger format, and thus the higher IQ (all else equal).

What matters from a photographic standpoint is the image you produce.

I don't think anyone disputes that. It's the IQ of the resulting photo as it relates to the amount of light that made up the photo that is being discussed.

And isn't there an argument that working within the limitations of your media produces the creativity and the strength of the image?

There is, indeed, such an argument. There are many who use cell phones as their cameras of choice, and I've seen excellent photos come from them. That said:

http://www.josephjamesphotography.com/equivalence/#iqvsqi

But what, exactly, is IQ, and what does it have to do with the "success" of a photo? The first step in defining "IQ" is to make the distinction between "image quality" and a "quality image". Many would take it as a given that if we have two photos of the same scene with the same composition then, all else equal as well, the photo with "higher IQ" would be "more successful". That is, the photo with "higher IQ", for example, would place better in a photo competition, would be more likely to sell, would sell for a higher price, etc. For sure, this may certainly be true for a large number of photos, such as a landscape photo displayed at a huge size. But it is important to acknowledge that there is a class of photography where image quality, as opposed to a quality image, is all but irrelevant (please see these outstanding photos, for example).

Furthermore, while one system may yield "higher IQ" than another, those differences may not be large enough to make any significant difference in the appeal of the photo, depending on the QT (quality threshold) of the viewer, the scene itself, the size at which the photo is displayed, and how closely it is scrutinized (see here for an interesting example of this point), and the processing applied to the photo. In other words, it is not merely whether System A has "higher IQ" than System B, but under what conditions it has higher IQ (and, indeed, which has "higher IQ" may flip-flop, depending on the conditions), and if the IQ is "enough higher" to make any significant difference.

For some photographers, IQ may be the most important aspect of photography. For others, it may play no role at all or simply be an added plus. But it is time well spent to reflect on just how important IQ is to our own photography, given that IQ is, at best, merely a means to achieving a quality image, and, at worst, completely irrelevant to the photo.

With all the disclaimers said about the relevance of IQ to the "success" of the photo, we can discuss what IQ is. The attributes of IQ include, but are not limited to:

Attributes of IQ do not include: subject, composition, focus accuracy, DOF, etc., which are attributes of system operation, available lenses, artistic design, and/or photographer skill. Of course, it's important to note that operational differences, such as focus accuracy, can have a substantial effect on the ability to capture a "high IQ" image. The "overall IQ" of a photo is a function of how the viewer subjectively weighs the individual objective components of IQ, which often depend greatly on the scene and how large the photo is displayed.

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