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05-12-2022, 07:35 PM - 1 Like   #31
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QuoteOriginally posted by acoufap Quote
If applying ETTR 1/3 stops may offer a slight advantage over 1/2 stops.
Found that setting when I started trying to figure out RAW (maybe before). At this point, it's just a habit I never gave a second thought. Now that I'm thinking... 1/2 and 1/3 stop increments aren't significant so I should probably change my camera settings. Going to do that now. Not peer pressure as much as I took a severely underexposed photo with he K3 III a couple weeks ago. Something like 3 or 4 stops. Anyway, I was able to recover that photo and it looked nearly identical to the next photo which was properly exposed. So 1/2 or 1/3 isn't going to make a difference.

05-12-2022, 08:01 PM - 1 Like   #32
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QuoteOriginally posted by jspi Quote
Not peer pressure as much as I took a severely underexposed photo with he K3 III a couple weeks ago. Something like 3 or 4 stops. Anyway, I was able to recover that photo and it looked nearly identical to the next photo which was properly exposed.
If the difference between the two photos was iso alone then there would be no visible difference (so long as you saved to raw.)
a shot at shutter X and aperture Y iso 1600 will look the same as a shot at Shutter X aperture Y iso 100 lightened 4 stops in your raw processor.
05-12-2022, 08:18 PM   #33
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QuoteOriginally posted by GUB Quote
Sympathies with the struggle but it gets better with practise.
It does. I never memorized the chart, but got to know it just through use. A practical way to familiarize yourself is to pay attention to what is happening with your shutter speed as you make changes to your aperture. Opening up your lens aperture by one stop, for instance, will result in double the shutter speed under the same lighting and subject. Keep in mind, with modern cameras the readings are approximate, as the cameras are capable of making fine in-between settings that are not showing exactly, and will probably not be recorded in EXIF with complete accuracy. But the readings are good enough for practical purposes.
05-13-2022, 04:10 AM - 1 Like   #34
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QuoteOriginally posted by UncleVanya Quote
Each stop of the square root of two apart.

1.414213562373095 * 5.6 = 7.919595949289332 (8).

The numbers are rounded and approximated.
As a result of this discussion, I checked my four Pentax digital cameras {Q-7, Q-S1, K-30, KP}.
All four are set for 1/2 steps - just like my film cameras.
I have no need for the “extra” precision.

05-13-2022, 12:52 PM   #35
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QuoteOriginally posted by RobA_Oz Quote
Assuming the pupil is circular (near enough, usually) that amount of light is therefore dependent on the square of the diameter
QuoteOriginally posted by jspi Quote
Assuming squares (yes, apertures are round and requires pi but that's not as simple)...
It does not matter what the shape of the aperture is - it could just as well look like a Maltese cross or a gingerbread man - if you increase the linear dimensions of any shape while keeping in proportion, its area increases by the mathematical square of the linear increase.

No photographer invokes pi when thinking about exposure. The sequence 1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45 - 64 gets printed into the brain, but it is noticed that alternate values double (near enough), and the ones between are a factor of 1.4 (square root of 2, near enough) out of step. The aperture area, and therefore the admitted light, doubles or halves from each of these f stops to the next.
05-13-2022, 02:43 PM   #36
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QuoteOriginally posted by jspi Quote
What is "One Stop"?
One stop later is the place where the bus slows down to a halt, again, to let people hop on or off. Two stops is a bit further away, that place where the doors ...


Or should that be "One Stop" of - what, precisely?


1 EV? Exposure stepping? A camera lens, perhaps? - DEFINITION: In optics, the f-stop of an optical system (such as a camera lens) is the ratio of the system's focal length to the diameter of the entrance pupil ("clear aperture").


So the f-stop is a ratio! It just happens that sometimes the ratio has special values (you know which values). But f/6.3 is a valid f-stop too. Also f/10 is a valid f-stop too. It's just a number, the result of a division. Focal length / diameter. A ratio. It just happens that people got used to a sequence of special numbers for historic reasons and for practical reasons. Related to exposure.


QuoteQuote:
Control, control, you must learn control!
Yoda said. “Feel the force!” Three parameters the exposure has. ISO, aperture, shutter speed.

First exercise, a Jedi mind trick: About ISO you shall forget. (hand waving down) That parameter - fixed. Aperture setting - fixed, as well. Now down the ladder you climb - of some special, known, memorized, shutter speeds. 1/4s -- 1/8s -- 1/15s -- 1/30s -- 1/60s -- 1/125s. Happens what? The exposure between those steps: it halves ! Up the ladder - the exposure doubles. Those, the usual bus stops they are, evenly spaced. +/- , [german: pi mal Daumen] Sort-of.

Second exercise: Keep ISO fixed. Keep shutter speed fixed. 1/125s. Now let's find some special numbers, ratios, that allow halving of exposure at each step. You'd have to mechanically control the aperture, through turning a ring, obtaining smaller and smaller diameters of the entrance pupil of the lens. Take note of the diameters that give those evenly spaced exposure steps. It just happens that the sequence of numbers, obtained as a ratio (focal length/diameter), is that special series:
1 -- 1.4 -- 2 --2.8 -- 4 -- 5.6 -- 8 and so on.

Science, there is. Physics. And some magic pixie dust.

Last edited by CristiC; 05-13-2022 at 02:55 PM. Reason: more pixie dust than attention there is
05-13-2022, 02:43 PM   #37
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Different people work differently. As for me, I prefer 1/3 stop increments set as my normal, for both fine points of exposure, exposure comp, and fine control of shutter speed for effect. I worked with 1//2 stop for many years, as this was the limit of control.

05-13-2022, 02:56 PM   #38
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QuoteOriginally posted by reh321 Quote
All four are set for 1/2 steps .
I keep half steps because my synch speed is 1/180 not 1/160. One can only maximize maximum synch in half steps.
05-13-2022, 03:32 PM - 1 Like   #39
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QuoteOriginally posted by swanlefitte Quote
I keep half steps because my synch speed is 1/180 not 1/160. One can only maximize maximum synch in half steps.
I think the crafty designers of the K-3 III have considered that quirk. They bumped the sync to 1/200 but you can set 1/200 even if you use half-stop steps.
05-13-2022, 05:36 PM   #40
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QuoteOriginally posted by swanlefitte Quote
I keep half steps because my synch speed is 1/180 not 1/160. One can only maximize maximum synch in half steps.
I ignore “synch speed” because the speed of AC current has always been more important to me -
as long as 1/60 is available, I’m happy. {but I do use half steps because they became ‘intuitive’ to me in the Age Of Film.
05-13-2022, 06:56 PM   #41
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QuoteOriginally posted by Lord Lucan Quote
It does not matter what the shape of the aperture is - it could just as well look like a Maltese cross or a gingerbread man - if you increase the linear dimensions of any shape while keeping in proportion, its area increases by the mathematical square of the linear increase.
The only other shapes I know of, that are used for aperture control are the odd stars, half-moons, arrays of dots etc that some exotic lens makers use. However, I agree that the square relationship (pi or no-pi) holds, pretty much.

I think we’ve all done this to death by now.
05-13-2022, 07:51 PM - 3 Likes   #42
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QuoteOriginally posted by RobA_Oz Quote
I think we’ve all done this to death by now.
Yes, my question (and more) has been thoroughly answered. Better to have extra info than to not have enough.

My K3 III is now set to 1/2 stops just to minimize the extra "effort". And 2 clicks per stop instead 3 means the wheel will last 33% longer, right??? No, I'm not actually asking...
05-14-2022, 05:32 AM   #43
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I think rote memorization is tedious, but the best way to learn the f stop progression. I got a little notebook and wrote out the f stops from f1.4 to f64 and memorized them while I walked the dog each day! I use half stops as they are easier for me to remember and understand, plus I can get where I want to be faster. I tried but gave up memorizing the shutter speeds as I predominantly shoot in Av and keep the minimum speed in mind. Shutter speed does have some oddballs such as why is one stop faster 1/60 actually 1/125 instead of 1/120??
05-14-2022, 06:23 AM - 1 Like   #44
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QuoteOriginally posted by que es tu Quote
... such as why is one stop faster 1/60 actually 1/125 instead of 1/120??
For historic reasons. Very old film cameras and their mechanical shutter mechanisms, especially mass-produced ones, were not precise. Label was 125 but the actual value was in a range 100-130 somewhere. Usual series was 125 - 250 - 500. None of them precise. Modern digital cameras have precise shutter timing but still use traditional numbers. Easier to remember as big numbers, as fractions or multiples of 1000. It doesn't matter if the actual value is 1/240 or 1/480 in a film camera. 250 or 500 is just a nicer number.
05-14-2022, 07:26 AM   #45
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QuoteOriginally posted by CristiC Quote
For historic reasons. Very old film cameras and their mechanical shutter mechanisms, especially mass-produced ones, were not precise. Label was 125 but the actual value was in a range 100-130 somewhere. Usual series was 125 - 250 - 500. None of them precise. Modern digital cameras have precise shutter timing but still use traditional numbers. Easier to remember as big numbers, as fractions or multiples of 1000. It doesn't matter if the actual value is 1/240 or 1/480 in a film camera. 250 or 500 is just a nicer number.
Cool! Thank you!!
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