"Crop-ability" of images?

Started 3 months ago | Discussions thread
john isaacs Veteran Member • Posts: 5,857
Re: Exposure vs Exposure

bobn2 wrote:

john isaacs wrote:

bobn2 wrote:

Iliah Borg wrote:

john isaacs wrote:

He can talk about Lux all he wants. No one cares.

If no one cares, why would Kodak mention lux 70 times on 24 pages of their "Basic Photographic Sensitometry Workbook" brochure?

I think in this case, 'he can talk about Lux all he wants' is shorthand for 'I'm incapable of following the discussion and don't want to admit to it,' and the statement 'No one cares' should have been prefixed with the words 'I hope'.

His definition is useless.

Not very clever, all those people like Hurter and Driffield, ISO, Kodak, Fujifilm, Ilford, Agfa and all the manufacturers that used and designed their products around that definition of exposure. Or the photographers like Adams that based their practice around it. Of course, it's to be expected, without the help of all those You Tube videos and Web explainers to put them right. I mean, what were they to do? They went to college and learned from people who actually know what they were talking about, and got their qualifications by satisfying examiners that they had learned it all properly. What a useless way of doing it. All that really matters is how many likes you get for your post. That tells you what's right and wrong.

And none of them had even heard of the 'Exposure Triangle', so really, how were they ever going to understand anything?

His insistence is futile.

Not quite as futile as someone who continues an argument in which their every contribution is yet another eloquent demonstration that they haven't a clue what they are talking about. It must be a lack of self-awareness.

This was all done in the film days, where the film was the sensor and the sensitivity was generally fixed. And so Shutter Speed and Aperture were the only parameters you had to deal with (although you might get involved with the film ASA if you needed to push the sensitivity for low light...but oh the noise).

What happened with digital was that base sensor sensitivity was easily modified by a gain adjustment (ISO), and could be modified on a per image basis. So shutter speed and aperture could be set within less rigid constraints, and ISO adjusted to increase the brightness of the image, avoid crushing blacks, and reduce noise. And, the product of the camera was not an exposed film, but a processed image. So exposure on the sensor became an intermediate step, and not a final product, of the camera. As a result, the term "Exposure" became synonymous with the image file. But ISO could now vary with each image (Exposure) and hence ISO became an important parameter of the Exposure.

And while none of those people you mention had heard of the "Exposure Triangle", they had heard of film speed ASA or DIN, and used it to set their exposure parameters. And the corresponding value of ISO is still used both in camera and in exposure meters to set exposure parameters. Including ISO.

Now you can claim forever that ISO is not an exposure parameter, but in practice it is. And if you want to derive anything about scene luminance from an image, you need to know what the ISO and Exposure Compensation values were set to, along with Shutter Speed and Aperture. And, of course, you need to know what the actual ISO of the camera is, and you need to know the actual transmissivity of the lens (including the effect of any filters that were used).

And of course, you have to close with another personal attack. Beats me.

 john isaacs's gear list:john isaacs's gear list
Panasonic Lumix DMC-GH4 Nikon D750 Olympus E-M5 II Nikon D500 Olympus E-M1 II +16 more
Post (hide subjects) Posted by
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
(unknown member)
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow