bobn2

bobn2

Lives in United Kingdom Worcestershire, United Kingdom
Joined on Aug 28, 2007

Comments

Total: 198, showing: 1 – 20
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In reply to:

CaMeRa QuEsT: This is an obvious warming-up ad for Canon's f/7.1 and slower lenses. This is an Amazon hawking website after all.

What does 'pro quality lens' mean when it's at home?

Link | Posted on Jul 2, 2020 at 18:14 UTC

I think another good example of the futility of trying to control lightness with exposure. If you expose so high as to burn out all the highlights, the only treatment that is viable is one with burnt out highlights. If you expose so as not to saturate the highlights, you can still give it the treatment that Pye suggests is better, and if you want to do it another way, you can have that too.

Link | Posted on Jun 26, 2020 at 20:11 UTC as 51st comment | 1 reply
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

VidJa: Who cares, go read a book on photography. This is all old news.

@alfn. ISO does not call the ISO ratings we use 'speed rating'. The two that are actually used , SOS and REI are both said by ISO to be exposure indices. The 'ISO speed' is determined now only by the saturation method, which CIPA doesn't sanction for Japanese cameras.
As for the 'exposure triangle', you are right, ISO is part of it. The question really is how useful is the triangle as a teaching aid, and, I suppose, whether peterson's original name, 'the photographic triangle' would be less misleading.

Link | Posted on Apr 11, 2020 at 10:16 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

MrBrightSide: I use a color-managed workflow with either raw files in Lightroom or with 16-bit Photoshop ProPhoto TIFFs.
If the new standard is only sRGB jpegs, what does this mean for people like me?

Simple enough to do your own tests, or to use sites like Photons to Photos or DxOmark, if you are really concerned. The question really is, how much trouble you want to put into optimising. You're already halfway there, faffing about with raw, TIFFs and proPhoto when many would tell you sRGB JPEGs are good enough for anybody.

Link | Posted on Apr 11, 2020 at 10:13 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Sacher Khoudari: In any camera review I have seen in the past years on this website, there has always been a comparison with competing cameras, especially in a studio scene. There the results were always compared at the same nominal ISO setting, ignoring the exposure settings.

Given the background information you are giving us here, is this approach in your reviews still applicable? I mean, shouldn't you rather compare the results of different cameras at the same exposure settings, instead at the same ISO setting?

Probably best to clarify, you test at the same exposures, not the same exposure settings - as I understand it the lighting can change so the settings can change to normalise exposure.

Link | Posted on Apr 10, 2020 at 22:32 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

D logH: ISO is simply an exposure index. The index gives a reference for an exposure system to calculate and aperture and shutter speed require for a particular light level and process to result in a specific response: images that look "normal" to the average viewer (or 18% gray is reproduced to the same basic reflectance). All ISO values take the entire process from exposure to the result into account, whether that is a direct positive process process (Digital images (JPEG/RAW), slides, or instant prints) or a negative/positive process (B&W and color negatives). The author clearly does not know that negatives are processed to a particular contrast index to match the printing media response. Basically, there is no substantial difference among ISO values for different photographic processes, just better implementation of exposure/processing systems to provide results.

I give DPreview 10 out of 10 for trying to educate its audience. However, this article has no real value.

But what is 'the aperture and shutter speed required for a particular light level'? Think on that one, and you'll realise that your argument is circular, because the only thing that determines the EV (f-number and exposure time) 'required' for a particular light level is the ISO setting. Think about it and re-read and you might find that the article has real value for you.

Link | Posted on Apr 10, 2020 at 22:30 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

MrBrightSide: I use a color-managed workflow with either raw files in Lightroom or with 16-bit Photoshop ProPhoto TIFFs.
If the new standard is only sRGB jpegs, what does this mean for people like me?

If you are using a raw workflow, your exposure management is best not conducted according to ISO ratings anyway. If you do so, you're probably leaving a lot of your camera's potential performance on the table (as it were).

Link | Posted on Apr 10, 2020 at 22:27 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Cocktail Time: “ Strictly speaking, ISO is a Switzerland-based standards body whose name derives from the greek word for ‘the same’. It is not an acronym, since the letter order would change in different languages, hence it shouldn’t be pronounced as a series of letters.”

Can you provide some provenance for this tale?

The scale was developed by the International Standards Organization, who didn’t apparently care about foreign translation any more than the American Standards Organization did when emulsion sensitivities were represented as ASA. Or the Deutches Institut fur Normung Cared when DIN was used. Or the french Appellation d'Origine Contrôlée (AOC) cares when certifying wines.

I believe therefore, that ISO, capitalized, is an acronym not a word and just like ASA should be pronounced that way: eye-ess-oh.

As photographers, I have every confidence that we can grind this pointless argument into a bitter dispute and I’m proud to have made my contribution.

@Cocktail Time. Isn't it pronounced 'Beezer'?

Link | Posted on Apr 10, 2020 at 19:18 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

UllerellU: Oh yes, I suppose that Cartier Bressom or Ansel Adams were fully aware of every technical entanglement that was hidden behind their cameras and the films they used ... I think it is better that you spend your time learning composition and improving your technique, very little It helps if you understand exactly how ISO works on a technical level (not on a practical level) if your photos are not up to it later.

Adams was the epitome of the technofreak nerd photographer. If you've ever read any of his stuff, to use him as an example of ignoring the technical side of the subject in favour of 'composition' is absurd.

Link | Posted on Apr 10, 2020 at 09:26 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

sirok: Now that these cameras have computers in them ISO/aperture/shutter speed could be continuously variable.

Nothing really to do with computers. Shutters have been 'continuously variable' since they became (analog) electronic, way back in the seventies. Iris apertures started out being continuously variable until they had click stops built-in for convenience. Movie lenses till have clickless aperture controls.

Link | Posted on Apr 10, 2020 at 09:23 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

gokhankuzu: ISO is the sensor`s collecting the light data less. The less collected data is artificially increased with the amplifier in the sensor. High ISO provides a fake photo not related to the captured image.

Amplification doesn't change the 'data', it just changes the units you express the data. Choose to count your money in pennies, you get a much bigger number, but it's still the same amount of money.
High ISO certainly doesn't provide a 'fake photo', in fact in many cameras it will give lower nose, and thus closer to the 'captured image'. There is a big question over what you think the 'captured image' is anyway.

Link | Posted on Apr 10, 2020 at 09:20 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

OzarkAggie: (a bit like turning up the volume on an audio amplifier. This is not true, and this misunderstanding can make it harder to understand what your camera is actually doing. )

( 'Lightening' includes both analog amplification and any subsequent digital processing.)

Well it sounds like it is "a bit like" since it is a part of the process. Just because an algorithm is used to sort the data and process it doesn't negate the signal amplification of the receiver. Without it the data would be less distinct.

@rrrremus - "When talking about analog gain or amplification it would be better to stick to the engineering correct term". I think one of the whole problems in this discussion is that people are apt to use technological analogies such as radios when they don't actually know how those things work - you are of course right about the volume control, it's actually an attenuator - though it does control the gain of the overall system. Where a radio is a good analogy though is that the input and outputs are different types of thing. RF energy in, sound energy out. So long as you're not using AM, the gain in the RF stage doesn't affect the volume.
Still I think the technical domain in which to think of ISO is computation, and to think of computed functions, in which case 'gain' becomes 'analog multiplication'.

Link | Posted on Apr 10, 2020 at 09:16 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Relaxed: Please consider the term flux (as in photon flux) instead of light density.

Flux is the correct technical word, however not very accessible to people without a technical education. The sort of article Richard is writing, it's very tricky to find words which give the right idea and which don't result in people throwing up their hands and saying 'I don't understand'. He's got an amount of that anyhow.

Link | Posted on Apr 10, 2020 at 07:47 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Hugo808: Thanks for the article. I look forward to understanding it one day....

I do have a question though, why are my fuji RAW files so dark when I open them in lightroom, it isn't just a histogram thing, they look way underexposed.

Your Fuji raw files aren't 'dark', they have no inherent lightness. LR is processing them to give you a visual preview, and the default profiles they use are too dark, compared with the ones that Fuji uses to do the in-camera processing.

Link | Posted on Apr 10, 2020 at 07:45 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

califleftyb: Doesn't anyone remember 18% grey?

That's the problem with digital, you can't drink the developer.

Link | Posted on Apr 9, 2020 at 22:23 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

SmilerGrogan: This is is a word-for-word lifting from the writings of a frequent forum poster named Bob, and grossly misstates the function and purpose of ISO.
Worse still the members of the ISO photo standards committee were not given a chance to respond to the criticism and provide readers with correct information.
Here's a list of people on the committee that need to be contacted before the next article is written. If contact info is needed, let me know.
Scott Foshee (Adobe)
Yoshi Shibahara (Fuji)
Ken Parulski— led the committee that developed the ISO standard for speed measurements (aKAP Innovation).

@ Iliah Borg - 'Orwellian. Since when explaining the standard became its criticism?' - This is the preferred practice in modern-day truth management. If you want your opinions to be the truth, then change the truth rather than your opinions.

Link | Posted on Apr 9, 2020 at 22:20 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Truman Prevatt: Even with Film ASA (ISO) was really only applicable to color negative film which had only one type of processing (developer/development protocol). With B&W film the film's ASA that one shot at was determined by the type of developer, the dilution of the developer, the agitation in the development process and the type of development, e..g., partial stand, water bath. The same film could and was shot at varying ASA depending on the development. Also in film the density of an image of an 18% gray card was used to define the ASA. To really calibrate one's B&W film one needed a densitometer - although there were short cuts.
http://www.mr-alvandi.com/technique/measuring-film-speed.html
So in these cases it was absolute based on - based on the above factors.

With digital - ISO is not even an approximation of the actual sensitive of the sensor. It is somewhat useless for those that shoot only raw.

@apestorm - That history of the transition from ASA to ISO sounds convincing - I don't know what happened before '93. As to Kodak, very often they will quote both an ISO 'speed', and other EIs based on different use cases, development regimes and so on. (for instance https://imaging.kodakalaris.com/sites/prod/files/files/resources/f4043_TMax_400.pdf) This explains some of their thinking: https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_newsletters_filmEss_06_Characteristics_of_Film.pdf

Link | Posted on Apr 9, 2020 at 22:17 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Horshack: "It's worth noting that that you cannot adjust the 'sensitivity' of a sensor. A camera's sensor will capture a certain proportion of the light that hits it, depending on the efficiency of its design."

I appreciate the pragmatic utility of this explanation because the amount of light captured and the base sensitivity of the photodiodes in a sensor represent 99.9% of what photographers need to know to understand ISO on digital cameras. However the noise introduced by the electronics/analog gain does technically represent part of the effective sensitivity of a sensor since sensitivity is a function of signal relative to noise and various ISO gain levels affect the amount of noise. For example, if sensor 'A' is 20% more sensitive to light than sensor 'B' but sensor 'A' has more read noise than 'B' then sensor 'A' is not 20% more sensitive to light because the only means to observe/use a sensor's signal is to sample/read it through the electronics that's designed around the sensor.

@Richard Butler - I told you Iliah would (rightly) prefer 'responsivity' ;-)

Link | Posted on Apr 9, 2020 at 20:44 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

Truman Prevatt: Even with Film ASA (ISO) was really only applicable to color negative film which had only one type of processing (developer/development protocol). With B&W film the film's ASA that one shot at was determined by the type of developer, the dilution of the developer, the agitation in the development process and the type of development, e..g., partial stand, water bath. The same film could and was shot at varying ASA depending on the development. Also in film the density of an image of an 18% gray card was used to define the ASA. To really calibrate one's B&W film one needed a densitometer - although there were short cuts.
http://www.mr-alvandi.com/technique/measuring-film-speed.html
So in these cases it was absolute based on - based on the above factors.

With digital - ISO is not even an approximation of the actual sensitive of the sensor. It is somewhat useless for those that shoot only raw.

@apestorm "Iso standards define film speed by using d 76 and a very specific testing procedure". Not quite correct. ASA speeds were based on a specific developer and process which was very similar (if not identical) to D76 - that is, it was the same formula, but D76 wasn't required. When ISO took over that changed to a requirement that the developer and development process be stated - allowing for films that were coupled with specific developers (and a bit of de-Americanisation).
"Everything else is exposure index not iso".
Not so. From the introduction to ISO 6:1993
Black-and-white films will generally provide excellent results in several different developers and processing conditions...This means a particular film may have several ISO speeds associated with it depending on the processes used. For this reason, it is important that manufacturers indicate the processing conditions for which ISO speed values are quoted.

Link | Posted on Apr 9, 2020 at 20:38 UTC
On article The ins and outs of ISO: What is ISO? (589 comments in total)
In reply to:

SmilerGrogan: This is is a word-for-word lifting from the writings of a frequent forum poster named Bob, and grossly misstates the function and purpose of ISO.
Worse still the members of the ISO photo standards committee were not given a chance to respond to the criticism and provide readers with correct information.
Here's a list of people on the committee that need to be contacted before the next article is written. If contact info is needed, let me know.
Scott Foshee (Adobe)
Yoshi Shibahara (Fuji)
Ken Parulski— led the committee that developed the ISO standard for speed measurements (aKAP Innovation).

If I'm the 'Bob' you refer to, I assure you, it isn't a 'word-for-word lifting' of anything I ever wrote.

Link | Posted on Apr 9, 2020 at 20:28 UTC
Total: 198, showing: 1 – 20
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