[UncleVanya]

I wonder if the auto -ISO functioning has changed then since the K7/K5? Certainly on these models it's only in Tav or green mode that the ISO would vary automatically..... I think I would find ISO AND exposure time changing in Av mode confusing. Have the later cameras added this, and can it be turned off in Av mode?

So bodies like the k50 are different and do offer auto ISO In many modes.

[mcgregni]

Thanks, I'd wondered about that. A bit puzzled though .... is it really helpful or intuitive to have one main 'priority', but then to have two other parameters changing around it with seemingly no control over which one moves each time ?

I can understand ISO changing in TAv (when you want to specifically hold an exact aperture and time value, say for a particular DOF as well as some motion aspect), and so the brightness has to be adjusted with ISO .... but is it any use at all in Av and Tv ?

Surely it is better to decide on a fixed ISO that maximises quality depending on the lighting?. Or maybe that decision can be relinquished to the camera sometimes ?

[elvinhaak]

Thanks, I'd wondered about that. A bit puzzled though .... is it really helpful or intuitive to have one main 'priority', but then to have two other parameters changing around it with seemingly no control over which one moves each time ?

I can understand ISO changing in TAv (when you want to specifically hold an exact aperture and time value, say for a particular DOF as well as some motion aspect), and so the brightness has to be adjusted with ISO .... but is it any use at all in Av and Tv ?

Surely it is better to decide on a fixed ISO that maximises quality depending on the lighting?. Or maybe that decision can be relinquished to the camera sometimes ?

It really depends on the situation and the shooter.
For example:
* If taking pictures of birds far away (with a telelens like 500 mms), I need a fixed aperture (for the minimum DOF and the quality of the lens), a relative high speed and don't care really what the ISO will be (lets say between 800 and 3200). So, fixed aperture, auto-ISO between 800 and 32 and then I can choose between [auto-ISO] or [auto-ISO and Auto-speed]. In the last case the camera will choose automatically and since I use auto-ISO already on high values the speed stays pretty high anyway with the long lenses (since it is within the programmed reach of the body that I use a long lens)
* if making a sports-picture, mostly closer, I don't generally need a fixed aperture so the aperture and ISO can change between borders but I do need to be able to choose a high speed or low speed with a twist of the wheel (sometimes want to choose to see the movement, the other time want to freeze the image).

In generally, depending on the kind of picture you are taking the ISO nowadays with the newer models is so well that for many pictures the ISO is not as important as the other factores (or just take a very fast and heavy lens!) if it stays below 1600 or 3200. At least, for me that is.
With the DA-50 I don't think that there are many situations where you need a real high ISO though. If you close the aperture to far to get a big DOF doing street-photography in the evening with a high speed or something like that the quality will be less due to the small aperture than due to the high ISO.

[Rondec]

Thanks, I'd wondered about that. A bit puzzled though .... is it really helpful or intuitive to have one main 'priority', but then to have two other parameters changing around it with seemingly no control over which one moves each time ?

I can understand ISO changing in TAv (when you want to specifically hold an exact aperture and time value, say for a particular DOF as well as some motion aspect), and so the brightness has to be adjusted with ISO .... but is it any use at all in Av and Tv ?

Surely it is better to decide on a fixed ISO that maximises quality depending on the lighting?. Or maybe that decision can be relinquished to the camera sometimes ?

As far as I know, all recent Pentax cameras can use an auto iso in Av mode. You set the range from the info screen. If you want to set a specific iso, hit the iso button and spin the rear dial and then hit the iso button again when you are there. If you want to get back to auto iso, hit the iso button and then the green button.

I tend to use auto iso with a range of 80 (or 100) to 1600. The camera will usually choose an iso that will give the minimum shutter speed as guesstimated by the camera -- usually 1.5 times the focal length. So, with the DA 50, the camera would let the shutter speed get down to 1/75 second before it bumps iso. But you can choose how quickly auto iso goes up to protect shutter speed too.

There is some more info on the green button: https://www.pentaxforums.com/forums/53-pentax-dslr-camera-articles/60081-usage-green-button.html

[mcgregni]

Thanks for those ideas guys. As a K7 user then ISO is not something that I'd be keen on letting rip! But roll on my next Pentax DSLR and I'm sure to be giving it a go.

[BruceBanner]

Hey Bruce, to answer the last question first, the f-stop is the same as aperture. When others were writing about the "A" setting they are referring to A type lenses which are the old manual film lenses with an A setting on the aperture ring (Congratulations on figuring out how to use legacy glass from the start BTW:-)). When they are placed on a digital camera and set to A you can control the aperture through the camera like your DA 50 lens. I think you do need to read your manual in order to get the most out of your camera. If you want an easier read I would refer you to Yvon Bourque's e-books on Pentax cameras: [url=[/url]. He goes through all the menu options and tells you what they're for. You may also want to do some brushing up on general photography as well. Brian Peterson's [U]Understanding Exposure[U] is a classic and very good read. I also found Digital Photography for Dummies very helpful when I was starting out. As to the question of the auto ISO parameters, I don't know if the K50 has it or not, but, on the K3 there is a menu setting that lets you control this. It gives three settings: slow,medium and fast. As for the Green Button, It has many functions, mainly as a kind of reset/zero setting, but, can be programed depending on mode.

PS. I just noticed that you said in your post that you have an SMC A 50/1.7. If that is the case you should be able to set the aperture ring to A and you don't need to bother with the green button to determine exposure and you should be able to use any mode. Give it a try:-).

Yeh, when I first attached the A lens and it didn't work my dad and I scratched our heads. I think it worked for his K-5 without needing to delve into the main menu settings, so a quick google taught us what to do to get the K-50 working with it

So all this time I have been using my K-50 with the SMC A 50/1.7 controlling the aperture soley from the lens ring, you mean I could have controlled the aperture using one of the e-dials just like the kit lens, should I have ticked a cross somewhere in the main menu? I guess it didn't matter much, in fact I have gotten institutionalized to using the ring on the lens that I am finding myself reaching with the DA and there is nothing there to twist!

Cheers for the heads up on the 'Yvon Bourque's e-books on Pentax cameras' book, that sounds right up my street. I tried looking at the manual a few times but when you're as clueless as me not a lot makes much sense, perhaps this book is more forgiving?

[sundr]

No menu setting required. Just set the aperture ring to A and leave it. The e-dials will control every thing. You need to enable aperture ring in the menu for lenses without an A on the aperture ring or if you wish to use the ring off the A setting. I hope you find the e-book useful. There's a lot to these cameras.

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Last edited by sundr; 04-18-2016 at 11:53 AM.

[RKKS08]

Just to put an end to the Auto-ISO confusion:
All models of the first three generations of Pentax DSLRs offered configurable Auto-ISO in all modes except M and B.
This made perfect sense if you remember Tav did not exist at that time, and till today is a Pentax special.

[OJGoreng]

I wonder if the auto -ISO functioning has changed then since the K7/K5? Certainly on these models it's only in Tav or green mode that the ISO would vary automatically.....

If you hold down the green button and then press the ISO button on a K5 in Av mode, with a manual lens attached, you engage a "hidden" auto-ISO function. It's a trick I learned here on the forum; AFAIK it's not in the camera user manual. Same goes for a K3; don't have a K7 to try it.

[Riggomatic]

If you hold down the green button and then press the ISO button on a K5 in Av mode, with a manual lens attached, you engage a "hidden" auto-ISO function. It's a trick I learned here on the forum; AFAIK it's not in the camera user manual. Same goes for a K3; don't have a K7 to try it.

So, I had to go try this. I popped my SMC-M 50 on my K-5 and switched to Av mode. If I click the ISO button, bottom right of the screen prompts to go to auto ISO by hitting the green button. Interesting. I've never noticed this. I usually hit the ISO button, and adjust with the dial. Once I adjust with the dial, auto ISO goes away.

Thanks