[CFWhitman]

Is this correct? I thought that in the camera there is electronic boosting of the signal, which contributes to high ISO noise. It is not just a software enhancement.

In the case of the K-7, ISO 1600 is the actual maximum ISO, and ISO 3200 is merely an extension of it.

Rob

Yes, you're correct. There is an amplifier that can be set to different levels just before the analog to digital converter. Also, as with the K-7, the highest ISO setting will often be done in software (firmware). Either type of amplification of the signal, though, will also amplify the noise. Whether one will cause more noise than the other in any particular case seems open to debate.

[pcarfan]

The K-7 goes up to iso 6400. This iso6400 actually has been said to be just an extension of iso 3200, and had to be accessed within the custom menu. AFAIK, the K-7 goes all the way to iso 3200 without firmware extrapolations.

P.S: For those who are interested, I have posed the question regarding proper exposure vs underexposing by two stops and pushing in PP to Gordon.B.Good, who is extremly knowledgeable on this kind of stuff. Hopefully he will respond, he usually does. I for one, will definitely follow his advice.

http://forums.dpreview.com/forums/read.asp?forum=1036&message=32804241

[filorp]

Hopefully he will respond, he usually does. I for one, will definitely follow his advice.

Hi gave an answer!!! Exactly what i have said.....
Re: Its not a deal breaker: Pentax SLR Talk Forum: Digital Photography Review

[Photomy]

Well, I guess to be more helpful as to what the camera is capable of, we also need to know the EV (Exposure Value at iso 100) of the light falling on the scene. This would avoid the +2 exp. compensation questions. (3, 4 ?) I assume dark objects will require more light to achieve a desired maximum noise level than light colored objects, but often we do not have control of the light - it is fixed. What we are trying to find out really is at what low EV limit (as used above) that the K7 can take a nice photo. Of course, this implies some kind of shutter speed lower limit I guess for hand holding (1/30?) and a practical aperture limit of say f2.8. Tripod can be used for the test but in real life with a tripod it is kind of moot if the scene does not move. Maybe practial EV guide limit for a dark object scene and an EV limit for a light object (higher reflection) scene. Obviously, these are estimates by the tester, but still would be valuable. If you can calculate the real EV (not exposure compensation but real EV at iso 100) for this test, that would be valuable. Or meter it with an ambient meter next time. I could estimate it if you had metered off of middle gray, but you did not. Thanks for the great contribution.

(I guess ISO 800 at 1/4 shutter and f4 = EV (iso 100) of 3. I guess it was a dark object scene for the camera to meter ISO 3200 and + comp. needed.)

LOL, No.

Anytime high iso and exposing to the right comes to play, this always crops up.

The consensus is that proper exposure is more important than the lowest iso and then pulling out the detail.

Also, think of it this way. +EV is totally arbitrary. If I used the spot metering, then it would meter off the darker areas and I may have to dial in -EV. So, EV compensation is totally dependent on my choice of metering. In the extreme, the spot metering can be run to the extreme by either getting the meter reading from the brightest part of the image or the darkest.

So, only thing we can do is to expose by the histogram. This is what I kept mentioning as having no clippings. So, +2 EV is irrelevant, what is important is whether the exposure renders the ideal histogram.

So, if I had 0 EV with the chosen metering, then it would mean underexposing the scene by two stops and using iso 800. This will require +2EV in post processing to get the ideal exposure. It is always better to use a higher iso to get proper exposure which will give the least amount of noise than to underexpose and recover which will show more noise. So, using 800 will be the wrong choice.

I knew the +2EV would throw some off, and thus me mentioning histogram, no clippings etc. Hopefully this clears things up for you.

---

Last edited by Photomy; 08-26-2009 at 09:08 AM.

[pcarfan]

If I get some time I will post an images with no exposure compensation (but, talking about EV here has much validity as mulling over whether a 2 sec. timer or the 12 sec timer or a remote should hvve been used). But, Photomy has a valid point about the luminoisty (?) of the scene it self.

But, I am getting what i needed to know form GG, so I am out of here. If I get some time I will post those images in a seperate thread.

In the interest of those who may actually be reading evreything wriiten here...just know that you CAN have P-TTL with bounced flash, it will work just fine.

[jgredline]

If I get some time I will post an images with no exposure compensation (but, talking about EV here has much validity as mulling over whether a 2 sec. timer or the 12 sec timer or a remote should hvve been used). But, Photomy has a valid point about the luminoisty (?) of the scene it self.

But, I am getting what i needed to know form GG, so I am out of here. If I get some time I will post those images in a seperate thread.

In the interest of those who may actually be reading evreything wriiten here...just know that you CAN have P-TTL with bounced flash, it will work just fine.

Hey for it's worth, thank you for taking the time to do this. I for one and many others I am sure appreciate the efforts...You have taught me much!
Thanks again,
javier

[pcarfan]

javier,

Thank you I appreciate it very much.

I am a one finger typist, and it takes for ever to go in circles...I didn't want anyone to think I am ignoring them just that I am sort of bored with this iso stuff as it is applicable here.

If you are interested check out what GBG in dpreview has to say on this (I provided the link earlier)...this guy knows his stuff and is capable of writing firmware upgrades for aberrant iso sensor behaviour. There is much to learn form him.

[tcom]

Here a few high ISO shots of the K-7 (posted earlier elsewhere on this forum):

1
K-7, DA*200, f/4, 1/100s, 1600iso


2
K-7, DA*200, f/4, 1/80s, 1600iso


3
K-7, DA*200, f/4, 1/100s, 640iso


4
K-7, DA*200, f/4, 1/125s, 1600iso


5
K-7, DA*200, f/4, 1/200s, 1600iso


6
K-7, DA*200, f/3.5, 1/200s, 1600iso


7
K-7, DA*55, f/2.8, 1/8s, 1250iso, SR is pretty impressive...


8
K-7, DA*55, f/1.8, 1/60s, 2000iso


9
K-7, DA*55, f/2.8, 1/50s, 1600iso


10
K-7, DA*200, f/4.5, 1/200s, 1600iso


11
K-7, DA*50-135, 70mm, f/2.8, 1600iso


12
K-7, DA*50-135, 55mm, f/2.8, 1/125s, 1600iso


13
K-7, DA*50-135, 55mm, f/2.8, 1/100s, 1600iso


14
K-7, DA*50-135, 58mm, f/2.8, 1/125s, 2500iso

[attack11]

Is this correct? I thought that in the camera there is electronic boosting of the signal, which contributes to high ISO noise. It is not just a software enhancement.

In the case of the K-7, ISO 1600 is the actual maximum ISO, and ISO 3200 is merely an extension of it.

Rob

you are correct sir. as you juice the sensor you get more noise. you also run into a scenario of auto-nr at various iso settings across different pentax bodies, which is undesirable.

[pcarfan]

Dominique, I saw them when you had posted them earlier. Infact I downloaded your full res. images and did NR and tweaked them BEFORE deciding to purchase the K-7. So, thank you for posting those.

[ivoire]

I use noisware professional plug-in for photoshop. It is ~$70, but IMO worth it.

-With this software, you can choose how much noise you want to remove form the shadows, how much you want to remove form the mid tones and how much you want to remove from the highlights. (My reason for picking this program)

-Also, you can choose to remove noise form certain colors as well (I don't use this but I will find use with certain images).

-Then you can choose how much detail you want to keep without introducing more noise. You choose the proper sharpness and contrast (maximum possible without adding more noise). You can also choose the level of edge smoothing .

- You can choose to reduce noise in the different frequencies too. The program analyzes the image and tells you which frequency has the most noise so you can choose to reduce more noise in those frequencies that has the most noise.

If you don't want to mess around with all this, then there is a pull down menu with varying noise reduction options with all this settings chosen for you. So you can pick one and the program will do it for you.

The individual controls may sound complex but very easy to use. They are done with sliders and you see changes in real time.

So, open the file, choose the luminance and chroma noise reduction amount to taste. Then go to tonal range and pick no noise reduction for highlights and medium for midtones (need to play around and see the image - look at areas with most noise and areas with fine detail) and choose close to max. reduction for shadows (again, check the noisy dark areas and fine detail areas and move the slider to taste). You can change the percentage of luminance noise and chroma noise as well as you do this. So, you go back and forth with these sliders constantly checking the dark zones for noise and fine detail areas for loss of detail.

Then you can change sharpness, contrast to taste as well. Going back and forth with these sliders until the darkest areas have most noise gone and yet the fine detail, area has detail left.

choosing noise reduction for various frequencies don't show much change. but as the program analyzes this, I just see the graph and reduce more in the frequencies that show the most noise.

Then I go to edge smoothing and see a sharp line in a dark area and chose the correct setting.

I am not that great at putting things into word as instructions. But, hopefully this helps.

Thanks again... I think this is well worth the $s and should prove very useful. Appreciate the post as I've gained quite a bit from this discussion

[wolfier]

Your opinion on shutter speeds faster than 1/4000 is interesting, to say the least. No doubt a lot of people don't need shutter speeds faster than 1/4000, but I believe 1/8000 is created for a purpose.

But you wouldn't really need to use ISO 3200 in daylight anyway. You'll find you won't have a shutter speed fast enough for such high sensitivity in those conditions. And when would you need a shutter speed faster than 1/4000?

Low-light is where it's mostly applied, and again mainly for being able to handhold a shot, otherwise you'd just set the camera on a tripod for stationary objects and allow for a longer exposure (and subsequently lower sensitivity).

[jbinpg]

@tcom: Is #10 a pic of Raine Maida of Our Lady Peace?

Jack