Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
05-12-2022, 03:20 AM   #16

Join Date: May 2014
Location: Linz
Photos: Albums
Posts: 2,539
QuoteOriginally posted by jspi Quote
Yes, memorizing a chart is what I'd like to avoid but I figure it's what I need to do. I've kind of developed a feel for it but I'm also often wrong (close, but wrong).
You could just count the number of clicks your control wheels make when changing your settings. If you haven't changed the default step size in the menu of the camera, you should get 1 stop after 3 clicks.

05-12-2022, 05:16 AM   #17

Join Date: May 2008
Location: Maryland
Photos: Gallery
Posts: 503
This is really pretty simple, you have the option in your custom setting in the camera to move the aperture up or down in either 1/2 step or 1/3 steps. If your custom menu is set to 1/3 step and your at F/6.3 and you need one stop of aperture you would simply open the aperture by three clicks on the wheel and that is one stop. Using an older lens with aperture ring in manual moves in 1/2 stops so two clicks up or down will be one stop.
05-12-2022, 05:17 AM   #18
StiffLegged's Avatar

Join Date: Jan 2018
Photos: Gallery
Posts: 3,186
Back in the mists of time, before many of us were even a twinkle in our grandparents’ eyes, someone came up with the variable aperture for a lens so these gentleman photographers weren’t limited to the f/8.3 maximum aperture of their Dallmeyer Double Anastigmatic glassware. In order to predict how many hours an exposure should be increased when using a smaller aperture, the control had a calibration scale which soon acquired click stops so you might accurately set these reduced apertures. The term “f stop” arose from these matters, or so it has always seemed to me. One click would usually halve (or double) the exposure although some manufacturers gave an option of half stops.

Later, the introduction of shutter mechanisms to accurately time exposures less than a second led to shutter speeds also being calibrated to give the photographer predictable exposures. Since f stops doubled (or halved) the exposure from one click to the next, it was practical to do the same with shutter speeds. Photographers soon grew to regard changing shutter speed by one click as increasing or decreasing exposure by “one stop” just as they did with aperture settings.

Electronics and finally digital gave us half or third stop variations in both shutter speed or aperture as well as sensitivity of the sensor. Halving the ISO is equivalent to halving the exposure (if nothing else changes).

Some things just need to be remembered.
05-12-2022, 06:11 AM - 1 Like   #19
retired sw engineer
Loyal Site Supporter
reh321's Avatar

Join Date: Nov 2014
Location: South Bend, IN, USA
Photos: Gallery | Albums
Posts: 21,435
QuoteOriginally posted by jspi Quote
I don't consider myself a beginner, more of an intermediate but I feel this is a question I should have grasped (memorized?) long ago. If I'm wrong on any of my information, feel free to educate me.

1 stop of adjustment is either halving or doubling the amount of light hitting the sensor. This can be done by adjusting the shutter speed or aperture. Increasing the sensitivity of the sensor (ISO) doesn't increase the amount of light but has the same effect (although it does increase noise).

Let's say I'm taking a photo at f8, 1/640s, and ISO 6400 but it's "1 stop" too dark.

I could increase ISO to 12,800 (1 stop) but it'll have more noise than I like.

Or I could slow the shutter speed to 1/320s (1 stop) but the action will be blurry.

So I must adjust the aperture. Going with halving/doubling to adjust one stop, the aperture would be f4 but I believe that would be closer to 2 stops.

I understand the math behind 1 stop of aperture but I can't calculate that on the fly. My assumption is I need to memorize which f stops are one full stop from the one below/above (I've been refusing to do that). But I though I'd ask if there's a quick way to figure it out without having to memorize a chart. For now, I just assume f8 to f4 is 2 stops so f6.3 is probably close to one stop? f4 to f2 is likely 2 stops so f4 to f3.2 is probably 1 stop. Assume... Probably... Just set to M, look at the expose meter, and hope it's close. Yeah, there's a bit of guessing and I'm most likely wrong but I have a big SD card so I'm faking my way to descent photos... Although a bit of memorization would be a small price to pay for throwing away less photos. Not to mention the extra time I'd have to be more creative while framing shots.
You’re being too scientific, and I - as a retired engineer - can actually say that. My eyes are not calibrated in ‘stops’ …. just in “too dark” or “too light” ….. and what I see is not in the field is not always what I see at the computer.

05-12-2022, 06:29 AM - 1 Like   #20
Site Supporter
Site Supporter

Join Date: Oct 2018
Posts: 230
Original Poster
QuoteOriginally posted by cmohr Quote
I noticed you mention 640th as a shutterspeed, this suggests you have your camera set for 1/3ev stops. to make it a bit simpler , change that to 1/2 stops, then each click of the wheel is a half stop, so then it's easy to go one stop, just two clicks of the wheel.
I pulled those numbers out of the air. But yes, the camera is set to 1/3 stops. That brings up a question of something I haven't tried... If I click the wheel 3 times, does that adjust the aperture 1 stop? That'll make me feel silly if the answer is really that simple and I never noticed it.

*Edit* Just saw the answer. So I need to click the wheel 3 times for 1 stop adjustment for any setting. Good to know, I should have picked up on that before now.

Thanks for all the responses, I have a few to read again later as there was more information given than what I'd asked for. Good stuff I'll need to read when I'm not in a hurry.

---------- Post added 05-12-22 at 01:45 PM ----------

QuoteOriginally posted by Papa_Joe Quote
This thread really makes me feel old. When I started photography no one would have mused about memorizing the f stops. Maybe the half stops for those bean counters. You had a lens with the f-stops on the aperture ring and a wheel with the exposure time on it and you had the values in your head quicker than you could think. Pentax owners were a little disadvantaged of course, they had to look through the viewfinder to see the shutter times on their M-series camera *).

*) Except the proud owners of a MX.
Yeah, while writing it I remembered that back in jr high I was able to tell my mom how much $$$ was in the shopping basket including the 6% sales tax. Now I just do a rough total and am generally within $10. Not old, just not part of my brain I exercise like I did 30+ years ago. OK, saying "30+ years ago" makes me feel old...

Last edited by jspi; 05-12-2022 at 06:39 AM.
05-12-2022, 07:28 AM   #21
Site Supporter
Site Supporter

Join Date: Jun 2008
Location: Idaho
Photos: Gallery
Posts: 1,817
Powers of 2:

1, 2, 4, 8, 16, 32, 64......

Then the square root of 2 as UncleVanya pointed out. Multiply the former or divide the next power of 2 by 1.41 to get the value in-between. Very little memory required.

1 f-stop or a change by 1.41 of the existing f-value alters the light on the film or sensor by a factor of 2 (also as UncleVanya pointed out).

Be careful when adjusting in f-stops by changing shutter speed (or ISO) as some cameras don't hit these value changes right on the head (but then there can be some degree of error in lens stops as well).

Last edited by Bob 256; 05-12-2022 at 07:34 AM.
05-12-2022, 07:55 AM   #22
swanlefitte's Avatar

Join Date: May 2015
Location: Minneapolis
Photos: Gallery
Posts: 3,906
The key is you know f/8 is one stop to dark from the start. Just keep reading the meter and dial.
If you know you are 1 stop too dark the easy way is to spin the wheel until you know you are just right. The same way I adjust the water in the shower.

05-12-2022, 08:44 AM   #23
Loyal Site Supporter
Loyal Site Supporter
Kevin B123's Avatar

Join Date: Jul 2016
Location: Hampshire
Photos: Gallery | Albums
Posts: 2,573
QuoteOriginally posted by jspi Quote
*Edit* Just saw the answer. So I need to click the wheel 3 times for 1 stop adjustment for any setting. Good to know, I should have picked up on that before now.
You can set your camera to make one click equal 1 EV, (which is a stop) for aperture and possibly speed and ISO (my cameras are not with me at the moment) so there is no need to remember anything really.
05-12-2022, 09:06 AM - 2 Likes   #24
Loyal Site Supporter
Loyal Site Supporter
pacerr's Avatar

Join Date: Jan 2008
Location: Paris, TN
Photos: Gallery | Albums
Posts: 3,251
If the goal is not to predict and define precise 'cubic glumps' of illumination or squishy bokeh effects but rather to produce pleasing images, your friend is instant review and histograms.
05-12-2022, 10:53 AM   #25
Loyal Site Supporter
Loyal Site Supporter

Join Date: Jul 2021
Location: Zuiderkempen - Grote Netewoud - Belgium
Photos: Gallery
Posts: 268
I recently saw this

It tries to explain the origin of the strange numbering convention.

But for me the bottom line is:
- either improving math skills, the divsion/multiplication by 1,4x (approx. square root of 2) and a bit of rounding.
Starting with 1 and multply each time by 1,4 + bit rounding gets you the full list.
Hint: why squareroot of 2? Aperture is about surface of lens opening, and a circular surface doubles when the radius is multiplied by V`2 = 1,4

- or using the tables, especially if half stops are needed or even worse 1/3 aperture stops....
Hint: with a little bit of luck, your lens might help: there is a aperture stop list on most lenses ( but not all, and some skip values, others use 1/2 stops, etc) ; also most lenses click when rotating aperture ring, either by 1 or 1/2 or 1/3 stops, check your lens manual or compare with a table to understand your lenses...
05-12-2022, 11:29 AM   #26
Site Supporter
Site Supporter
Alex645's Avatar

Join Date: May 2015
Location: Kaneohe, HI
Photos: Albums
Posts: 3,296
QuoteOriginally posted by jspi Quote
*Edit* Just saw the answer. So I need to click the wheel 3 times for 1 stop adjustment for any setting. Good to know, I should have picked up on that before now.
The default 1/3 stop increments makes sense when and if you're either using an auto exposure mode or in a situation where quickly changing apertures or shutter speeds is not critical. But if the ability to quickly jump several stops is important, then that's where changing the EV increments to 1/2 stops is helpful. Then you're only counting two clicks. And if you're not pixel peeping, the ultimate for speed and simplicity of learning manual exposures is with whole stops.
05-12-2022, 11:48 AM   #27
Loyal Site Supporter
Loyal Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 5,635
I always use 1/2 stop increments on my camera. It is easier when making shutter speed or aperture adjustments to comply with an external meter reading. "Two clicks is one stop"

When processing images, the difference between a half and a third stop is irrelevant.
05-12-2022, 12:08 PM - 1 Like   #28
Site Supporter
Site Supporter
acoufap's Avatar

Join Date: Jan 2011
Location: Munich, Germany
Photos: Gallery | Albums
Posts: 3,227
If applying ETTR 1/3 stops may offer a slight advantage over 1/2 stops.
05-12-2022, 12:22 PM - 1 Like   #29
Site Supporter
Site Supporter
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 6,056
I believe the third-stop system is another one of those measurement trickery propaganda inventions of Big Photo.
05-12-2022, 02:11 PM   #30
Loyal Site Supporter
Loyal Site Supporter
pschlute's Avatar

Join Date: Mar 2007
Location: Surrey, UK
Photos: Gallery
Posts: 5,635
QuoteOriginally posted by acoufap Quote
If applying ETTR 1/3 stops may offer a slight advantage over 1/2 stops.
....Gets calculator out and taps furiously away on it

  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
answer, aperture, bit, camera, chart, click, f4, f8, half, increase, iso, light, noise, owners, pentax help, photography, sensor, troubleshooting, wheel
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
645Z + FA 645 55mm: Sharpest f-stop at f8 or stop down? Hyperfocal issues.... steve645z Pentax Medium Format 31 01-09-2017 08:08 AM
People Stop stop... no more pictures! ppppsssstttt Pentax K-3 Photo Contest 2 06-03-2014 04:19 PM
Don't say Pentax "Q" in French ... "Q" = "cul" = "A--" Jean Poitiers Pentax Q 52 11-10-2013 06:25 AM
Misc When i say stop it means stop ! deadprez Post Your Photos! 3 08-02-2011 07:38 AM

All times are GMT -7. The time now is 01:12 PM. | See also:, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]