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01-02-2015, 07:41 AM   #1
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K-S1 exposure modes

I downloaded the operating manual and have been looking at how the modes work to see how I might use the camera. There seem to be two lots of ISO settings. There's ISO-AUTO where you can set the top of the range allowed. And there's ISO which is a fixed ISO. Which of these is used under which conditions? Looking at the exposure modes on P. 42, for Tv and Av, the table says I can change the sensitivity - but is this done via the menus? In TAv, can I cycle through and use the wheel to set all the parameters (Speed/aperture/sensitivity)? Which then is the camera altering to maintain a correct exposure?

Thanks for insights! I bought my last Pentax in the early 90s and have just had occasional access to SWMBO's K-100D Super - and I think she uses that largely in P mode.

01-02-2015, 08:20 AM   #2
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I use auto-ISO most of the time (I think most people do), but when I want more control (say, to reduce noise), I'll go with manual ISO. Two recent examples: (1) shooting Christmas lights outdoors at night, I let the camera decide ISO while doing 'walking around' shots, but when I got out the tripod and planned some long exposures, I locked ISO to 100 for minimal noise, (2) shooting moving toy trains indoors in not-great light. I set the ISO really high to get a shutter speed fast enough to stop motion, and just accepted that there would be more noise.

When you want to manually select an ISO, there is a dedicated button on the 4-way controller. You just hit the ISO button, then choose either the range of auto-ISO (upper selection) or the fixed ISO (lower selection) that you want, then hit OK. It's really easy to do.

It's pretty much the same as the K100D Super, except that I rarely let my K100D auto-select higher than ISO 800, and I'm comfortable letting the K-S1 go to ISO 3200. (Of course you can go much higher, but there will be more noise - it's a matter of taste and how much post-processing you are willing to do).
01-02-2015, 04:41 PM   #3
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This brought up a question about P mode I hadn't researched yet, so I'm glad you asked the question. I know you weren't really asking about that, but I thought about it when I was thinking about my answer to the original question.

To answer your question, as THoog pointed out, you do have two options for ISO - auto and fixed. In general, I leave the camera set to auto, unless I want something specific. For instance, if I want the best quality, I'll set it to ISO 100, to keep noise levels down. There's lots of times I want that.

If you want control over all 3 attributes for exposure (aperture, shutter speed and ISO), you have to use M mode. It doesn't matter if you have the camera set to Auto ISO, it will automatically shift to fixed and the lowest ISO setting (unless you already have the camera set to fixed and a higher ISO, at least I think it will, I use auto ISO so much, that's how I usually have it set when I switch to manual). I've been using M a fair amount recently since I've been playing around with off-camera flash recently).

The next exception to how the camera is set for ISO is the TAv mode. It doesn't matter how the camera is set for ISO, it will always work on auto. You can only change the shutter speed and aperture in this mode, the camera will automatically choose the ISO to give you the correct exposure. That's handy for me, I'm not as steady as I used to be, so I often will set the shutter speed fast enough to avoid camera shake, and the aperture for the dof I want, then let the camera sort out how to (hopefully) get the right exposure.

Both auto and fixed ISO work for Av, Tv, and P modes.

The question I had to look up on the P mode, has to do with what values you can change in P mode. Certain cameras have been able to change either Tv or Av in P mode. I often use this when out taking snaps or traveling, it allows me to let the camera do it all if I don't care about the settings, or let's me override one factor for one or 2 shots, if I don't like what the camera chooses. But I've always used this on a camera with 2 wheels, so I didn't know if the K-S1 was capable of doing this. It does, but you have to specify which you want to change in a menu, so it isn't as flexible as a two wheel camera, but I don't think it's a big deal. I'll probably set the camera to allow me to change the aperture because that's the value I'm more likely going to want to change when I'm taking snaps. If I want to change the shutter speed, it's easy to change modes.
01-03-2015, 04:59 AM   #4
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Thanks. I read the doccy a number of times but felt that in the detail, it was unclear. F'rinstance, it was unclear that one could force it (modulo the exceptions you note) it to use ISO or ISO AUTO. I was more reading that you could set both, but it would always use a particular one depending on what it was doing.

It also seems that one might use one of the top plate buttons to switch between what the wheel varies. But then I thought OK, here I am in TAv, I've just set the shutter speed, I then set the aperture, and the only way the camera can now get the exposure right is for it to undo the shutter setting I just did. But if you're saying that poor old ISO is at the bottom of the food chain, and will get modified as necessary with no say in the matter, then it makes more sense.

01-03-2015, 02:50 PM   #5
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QuoteOriginally posted by Clothears Quote
It also seems that one might use one of the top plate buttons to switch between what the wheel varies. But then I thought OK, here I am in TAv, I've just set the shutter speed, I then set the aperture, and the only way the camera can now get the exposure right is for it to undo the shutter setting I just did. But if you're saying that poor old ISO is at the bottom of the food chain, and will get modified as necessary with no say in the matter, then it makes more sense.
I love your "ISO is at the bottom of the food chain" explanation for it, a good analogy. Each of the modes except for M and perhaps B have a different food chain. Need to experiment with the B mode - the owners manual is dreadful about explaining it. I found only 2 very brief mentions in the index, I need to read further to see if I can do what I think I might want to do.

---------- Post added 01-03-15 at 02:44 PM ----------

Ok - I've played a bit with the B mode. It works the way I was hoping it would - you can set the camera to either keep the shutter open as long as you hold the shutter down, or else set it to open with one push of the shutter button and not close until you push the shutter again. What I vaguely remembered with the other camera was that you couldn't use the second option with a wireless remote for some reason or else it wasn't an option or something - this feature wasn't important to me and I could easily have been mistaken. I had a wired remote that had a shutter lock option on it, so the few times I used B mode I used it. Thanks to a dark closet and f22 I just verified that option 2 does work with a wireless remote on the K-S1. Also I noticed that the sensor on the front of the camera is enough on one side that you can use your right hand to trigger the camera without having your hand in the frame, especially if you are shooting in the dark with long exposures. Very cool! Hope to try my hand at star trails tonight.
01-05-2015, 03:06 PM   #6
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QuoteOriginally posted by mtngal Quote
Thanks to a dark closet and f22 I just verified that option 2 does work with a wireless remote on the K-S1. Also I noticed that the sensor on the front of the camera is enough on one side that you can use your right hand to trigger the camera without having your hand in the frame, especially if you are shooting in the dark with long exposures. Very cool! Hope to try my hand at star trails tonight.
Shooting the K-S1 in the closet... I know it's not a very popular camera around here, but has it gotten that bad?

After playing around this weekend in a museum with a lot of fluorescent lights, I'm of the opinion that the K-S1's AWB does better with fluorescents than any of my 16MP bodies. Anyone seen the same?
01-05-2015, 09:52 PM   #7
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QuoteOriginally posted by THoog Quote
Shooting the K-S1 in the closet... I know it's not a very popular camera around here, but has it gotten that bad?
ROTFL! Love it!!!

QuoteQuote:
After playing around this weekend in a museum with a lot of fluorescent lights, I'm of the opinion that the K-S1's AWB does better with fluorescents than any of my 16MP bodies. Anyone seen the same?
Love it when someone brings up a topic that piques my interest, especially when I'm feeling otherwise uncreative. So I took a few quick snaps around my office, which has low energy fluorescent fixtures. The bulbs are higher output/more energy efficient than older fixtures. The color isn't quite the usual cool white, either. My conclusion was that the K-S1 struggled about the same as any of the other Pentax dSLR cameras I've used under the same lighting conditions. Perhaps if the fixture had older, more common fluorescent bulbs, it would be better.

I shoot raw + and at the moment the picture mode is set to b&w. I like b&w and have been sort-of playing around with it. Seeing the camera's version on the LCD gives me an idea of the picture would look all right in b&w. I quite often just use the jpg version, rather than converting the raw file and tweaking it, if I decide to stick with b&w. Since I shoot raw + I still have the color file for the times when I want color. I wondered if LR would recognize any difference between AWB and the multi-AWB. I don't know if it would differ from a jpg version since I didn't bother changing the picture mode to something other than b&w. But as far as the DNG raw file goes, they were both the same - half the frame was through a window and half was the interior of my office and both raw files looked the same. The camera did do better with the white balance when the light was only from the overhead fixtures.

Not to highjack this thread, but if you are interested in the shots (they are not much, just quick snaps) you can find them here: Zenfolio | Mtngal's Photos | 2015 Year in Photos - taken from the raw file that includes white paper with the white balance unchanged; Zenfolio | Mtngal's Photos | 2015 Year in Photos - a different photo but a similar subject where I corrected the white balance in LR; Zenfolio | Mtngal's Photos | 2015 Year in Photos - the half window, half interior picture. How do you like the monitor - when was the last time you saw one like that???

Anyway, thanks for the incentive to get the camera out and experiment, always love the opportunity.
01-06-2015, 05:02 PM   #8
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The K-S1 thinks the CFLs in my office lean towards pink, and I don't agree. This museum was formerly a tool factory, so it's lit with lots of industrial 8' tubes. I haven't really dug into the .DNGs, but the K-5 and K-01 seem to think everything is yellow. The K-S1 leans more to the cool side, not necessarily correct, but a little closer to what I think my eyes see. The weird thing (to me - maybe it's obvious to someone else) is that in two of the large rooms, I get terrible flare and ghosting off the lights (no matter what lens I use), but it's not as bad in the third. I think they are all the same color bulbs. To my eye, all three rooms are lit equally badly (they don't have any heat or A/C, so winter doesn't do the lights any favors).

I've got a 21" Viewsonic monitor that might be as old. I haven't replaced it because (1) it was basically free, (2) it refuses to actually die, and (3) it's huge and weighs at least 60lbs, and carrying it downstairs is not going to be fun.

01-07-2015, 02:12 AM   #9
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QuoteOriginally posted by Clothears Quote

It also seems that one might use one of the top plate buttons to switch between what the wheel varies.
The Exposure Compensation button, Clothears. :-)
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