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The lounge Relax, take a break from photo and camera talk - have a chat about something else for a change. Just keep it clean and polite!

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Old 17th April 2017
Ricoh Ricoh is offline
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Depth of field and crop factor

I found this interesting, especially the bit about ISO...

https://petapixel.com/2017/03/29/dis...d-crop-factor/
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Old 17th April 2017
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Re: Depth of field and crop factor

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Originally Posted by Ricoh View Post
I found this interesting, especially the bit about ISO...

https://petapixel.com/2017/03/29/dis...d-crop-factor/
Well, it's just two stops...

- u43 is half the linear dimensions of FF and a quarter the area.

So:

- effective focal length follows the linear dimensions - x2
- aperture and ISO (all other things equal - see below) follow the area - x4

So, is ISO 200 really equiv to ISO 800 on FF? It's probably less since the pixel density on u43 is a lot higher than on FF (e.g. the E-M1ii's 20Mp sensor would be equiv to an 80Mp FF sensor). Most practical tests show a difference of less than 2 stops (maybe 1.5). However, to a first approximation 2 stops is as good as anything.
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Old 18th April 2017
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Re: Depth of field and crop factor

Yes indeed Paul, it's just I hadn't thought about ISO in this way.
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Old 18th April 2017
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Re: Depth of field and crop factor

Many thanks indeed for posting that - excellent (although you do need to watch both videos to get the full, correct story).

That's the first time I've seen a correct, clear and reasonably comprehensive description with well-chosen image examples, and the speedbooster stuff is good as well.

I'll copy it round a few people locally who I know will find it interesting.

I'd just criticize the obsession he and many others have with manufacturers 'lying' to us - that is unfair. They are just following the naming conventions of our times (which emphasize focal length equivalence and ignore the other areas). One might as well say all full frame camera manufacturers lie to us since proper full frame is 10"x8"! It shows how ignorant and easily-led by the technology nose most consumers are!

He mentions Tony Northrup's videos, who does show some nice example images, but TN completely glosses over the ISO issue, which make his 'equivalence' point unintelligible. (TN's also nauseatingly smarmy...)

There are one or two omissions, though.

Perhaps not surprisingly (!) he chose to ignore shutter speed (actually saying it wasn't relevant). Indeed it isn't relevant mostly when your camera is on a tripod, but for stationary or slowly-moving subjects, since smaller sensor cameras have better IS the photographer is able to make up for some of the ISO noise disadvantages by handholding at slower shutter speeds.

Secondly, sensor technology is demonstrably improving hand over fist, especially in dynamic range. So smaller sensors today (especially Sony ones) are able to give better dynamic range performance despite the smaller light density per pixel (case in point is the 2/3 to 1 stop better dynamic range of the m4/3 E-M1ii sensor compared to that of the Canon 7D mkii APSC sensor at all ISOs up to around 18000).

It also ignores the point that one should really consider how good an image one actually needs for one's purposes rather than just obsessing over how to create the ultimately low noise, low DoF and high resolution one that technology is capable of providing.

A minor and specialist point, but there are some lenses appearing now that deliberately break the connection he mentioned between light transmission 'stops' in comparison with F-stops. For example, the Sony FE 100mm F2.8 STF G-Master ( https://www.sony.co.uk/electronics/c...es/sel100f28gm ) has a couple of stops lower light transmission (T-stop) than its F-stop would suggest, and this allows narrow aperture for portraits and it gives lovely bokeh. Presumably creating all that dreamy background results in more absorption within the optic.
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Old 18th April 2017
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Re: Depth of field and crop factor

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Originally Posted by drmarkf View Post
So smaller sensors today (especially Sony ones) are able to give better dynamic range performance despite the smaller light density per pixel (case in point is the 2/3 to 1 stop better dynamic range of the m4/3 E-M1ii sensor compared to that of the Canon 7D mkii APSC sensor at all ISOs up to around 18000).
Canon sensors have been lagging the curve for years. The APSC sensor in the 7Dii is nothing special at all and is bettered by the E-M1ii.

Interestingly Canon are still the number one vendor in the prosumer (hate the word) ILC camera world, so a sub-par sensor seemingly isn't that important!
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Old 18th April 2017
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Re: Depth of field and crop factor

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Canon sensors have been lagging the curve for years. The APSC sensor in the 7Dii is nothing special at all and is bettered by the E-M1ii.

Interestingly Canon are still the number one vendor in the prosumer (hate the word) ILC camera world, so a sub-par sensor seemingly isn't that important!
Well, the ultimate sensor isn't all there is to photography (see my 9th para above!).

It also shows the power of marketing, in that amateurs have all heard of Canon, their 'expert' mates mostly use it, and there's all those white lenses on show at their local footy ground.

Of more genuine value is the perception (probably true) that Canon make the most reliable and toughest kit, that will just work and always get the shot (even if it's got more noise...).
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Old 19th April 2017
Harold Gough Harold Gough is offline
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Re: Depth of field and crop factor

NB Seeing that a speed booster adapter makes the image circle smaller, do not use with tilt or shift lenses.

Harold
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Old 19th April 2017
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Re: Depth of field and crop factor

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Originally Posted by drmarkf View Post
Of more genuine value is the perception (probably true) that Canon make the most reliable and toughest kit, that will just work and always get the shot (even if it's got more noise...).
And it does just work.

I have Canon PowerShot G9 and G11 cameras that I have owned since new. They don't do anything particularly well, but they always work when I want them to.

And unlike Olympus, I know I can grab one at any time and not be greeted by the dreaded "Battery Empty" message; even after six months or more since last being used.

My Olympus batteries seem to run themselves flat within a month even if they are removed from the camera, although they do seem to be getting better.

There again, my OM2Sp and OM4Ti had form in that department.
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