VPN has a nasty friend!

Started Mar 16, 2007 | Discussions
Dave Santora Senior Member • Posts: 2,552
VPN has a nasty friend!

As many of you know I have found the VPN issue (and more importantly Pentax's ignorance of it) to be an issue that needs resolving. Anyway, I was just taking some random house pictures with my FA50 f1.4 and noticed some underexposure VPN at iso1600 (where it really only occurs - if you stay a bit overexposed or lower ISO it can be hidden).

So I decided to try a test... I shot a 5-shot exposure bracket sequence of a HP LaserJet printer hiding under a desk in low light. This image, which is about 2 stops underexposed, shows not only GordonBGood's nemesis - VPN, it clearly shows HPN (horizontal pattern noise). The combination creates a pattern noise grid that is very evident.

I realize this intentional underexposure would never be evident in a properly exposed shot - and I make an effort to avoid this at all costs (I now considering shooting exp +0.7 in low light situtations just to avoid it). But, this pattern may help Pentax or anyone else trying to see the VPN (and now noticeable HPN) hopefully work on a fix for it.

I really covet my K10d and now will not par with it (even with this odd issue - that can be avoided 99% of the time). But I hope the K10d successor has this problem fixed (and a usable iso3200)

Thanks for reading. If you're going to bash, complain (about the VPN issue), or otherwise discount it - save your keyboard - this post is for people interested in fixing a problem - not arguing about it...

K10D, iso1600, 1/80s, f4.0, FA50 f1.4 lens, custom WB, handheld, converted pef file from ACR 3.7 - no changes, cropped - nothing else

Jonson PL Veteran Member • Posts: 3,600
Re: VPN has a nasty friend!

…but DPr have some very predictable users sometimes…

I rarely have the need beyond ISO 800, especially with SR.

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Kind regards
Sune

  • A talented photographer doesn’t miss the shots, he improves his technique

OP Dave Santora Senior Member • Posts: 2,552
Strange avoidance

People must be sick of discussing this - hey, me too! Maybe Pentax is getting sick of hearing about it, and fixing it for my K1D that I will buy late next year after many delays
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BTG308 Contributing Member • Posts: 941
Re: VPN has a nasty friend!

Dave Santora wrote:

K10D, iso1600, 1/80s, f4.0, FA50 f1.4 lens, custom WB, handheld,
converted pef file from ACR 3.7 - no changes, cropped - nothing else

BG-2 grip? I'm planning to run a series of tests, maybe later today.

I was thinking of shooting against a dark featureless wall (to avoid any surface textures showing up as banding) with SR on/off, NR on/off and grip on/off and all combinations thereof. I'm even considering using my pinhole body cap to exclude any lens interference.
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DS_Dave Senior Member • Posts: 2,261
Re: VPN has a nasty friend!

I guess...they also reply to posts too

I do use ISO 800+ ...a tripod or SR cant fix a moving subject in low light...

Dave

Jonson PL wrote:

…but DPr have some very predictable users sometimes…

I rarely have the need beyond ISO 800, especially with SR.

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OP Dave Santora Senior Member • Posts: 2,552
Let us know what you see

I think this is the first time I have seem any horizontal banding - Even GordonBGood has not mentioned this
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Andreas K. Ehrenreich
Andreas K. Ehrenreich Regular Member • Posts: 403
Re: Strange avoidance

Dave Santora wrote:

People must be sick of discussing this - hey, me too! Maybe Pentax
is getting sick of hearing about it, and fixing it for my K1D that
I will buy late next year after many delays
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Don´t expect too much it will be a K20D ....
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steelski Senior Member • Posts: 2,555
Re: VPN has a nasty friend!

thankfully I dont take very very very underexposed pictures of printers in the dark.
The whole problem only occurs with photos that are vasty wrong and theoretical.

I did take a picture that I thought would be cool at 1600iso and I thought that VPN ruined my picture. The truth is that I needed a tipod and no amount of Iso (I could have if I had 19200 available...work on it Pentax )
and SR would have helped.

OP Dave Santora Senior Member • Posts: 2,552
...not the end of the world

but they definitely should improve on it (if not eliminate)

Also, the reason for my thread was to show a very evident horizontal banding that no one else has either experienced or bothered to bring up - and I'm guessing others (if noticed) would have brought it up.

My camera , by the way, seems to exhibit the same amount of VPN as other K10D models - so I don't believe it is a problem specific to my camera - I hope not!
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Jonas B Forum Pro • Posts: 14,596
Re: VPN has a nasty friend!

steelski wrote:

thankfully I dont take very very very underexposed pictures of
printers in the dark.
The whole problem only occurs with photos that are vasty wrong and
theoretical.

steelski, did you have a look at the correctly exposed pictures suffering from VPN?

joemeek Regular Member • Posts: 157
Re: VPN has a nasty friend!

Well it took me until the sun went down enough that my room is pretty dark - but yes I see both Vertical and Horizontal bands.

I also saw horizontal bands quite frequently on my DS at high iso in shadow areas, although firmware cut this down a little - but not completely.

Right now I've seen obvious VPN on two occasions - on an area of an image equivalent to about ISO 6400 if it had been exposed properly. If I bump exposure, brightness & fill light up to maximum in Lightroom I've even made it appear in areas that would be considered Zone 0 in the Zone system at ISO 100 - ie not visible in print.

The only thing that would make me worry is if I shot weddings - I'd need ISO 1600 relatively frequently & I don't think the quality is high enough for reasonable enlargements even with NR. I did a recent shoot at ISO 800 documenting a shoot in a studio, & the noise in the black clothing was pretty awful - not VPN, but still not great. 12x8 Prints are ok, but I don't think I'd want to chance 1600Iso for pro work. Same goes for D200/D80/Alpha.

johnami
johnami Senior Member • Posts: 1,211
Re: VPN has a nasty friend!

What a boring image, and before you complain, yes I know you are discussing a technical point, but why not do it with something a little more interesting than a 'printer' in very low light.

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OP Dave Santora Senior Member • Posts: 2,552
looks like some people just can't see it

This is not a thread for denial. This is a thread related to the solving of a problem. If you have never seen it (and more importantly are not part of the group trying to solve it), then feel free to respond to other threads.

VPN is not a UFO or crop circle - it is a real issue that occurs for a lot of K10D owners on a regular basis. Yes, proper exposure usually avoids it. But, many have seen it in proper exposures and even at iso400 and below. And there are times when the camera meters wrong or we as shooters incorrectly expose (both under-exposure), and in this case the VPN makes it very difficult to save the shots in PP.

Try to help or provide input that is beneficial - saying you never experience it accomplishes nothing. Some people never experience camera shake either, they shoot in good light wide open.
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OP Dave Santora Senior Member • Posts: 2,552
Tests are boring...

Why do you think scientists are boring boring people. I have some that are friends: nice, intelligent, and boring...
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Jonson PL Veteran Member • Posts: 3,600
Re: VPN has a nasty friend!

DS_Dave wrote:

I guess...they also reply to posts too

I do use ISO 800+ ...a tripod or SR cant fix a moving subject in
low light...

So buy faster glass (I have the 50 mm f/1.2) or use flash; big deal.

Personally I don’t lurk around in the dark to take pictures of printers.

If you need the high ISO, then go for the K100. Or get a deal on the *ist D, it is still a very fine camera, and prices will get better.

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Sune

  • A talented photographer doesn’t miss the shots, he improves his technique

johnami
johnami Senior Member • Posts: 1,211
Re: Tests are boring...

I don't think scientist are boring, but politicians can be really boring and there are plenty of photos of them in the press everyday.
Photos don't have to be boring, that's all I am saying.
I am sure this 'banding' problem will be 'licked'" one day.
If you know what the limit of your machine is, then you don't go over it.
But thanks for the article. It is interesting;-)

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Jonas B Forum Pro • Posts: 14,596
Re: looks like some people just can't see it

I am in denial? Or is your reply just misplaced Dave?

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Jonas

Jonas B Forum Pro • Posts: 14,596
Re: VPN has a nasty friend!

Jonson PL wrote:

DS_Dave wrote:

I guess...they also reply to posts too

I do use ISO 800+ ...a tripod or SR cant fix a moving subject in
low light...

So buy faster glass (I have the 50 mm f/1.2) or use flash; big deal.

Sune, really, how can you tell people if a problem is a problem or not to them?

Personally I don’t lurk around in the dark to take pictures of
printers.

As we have seen VPN in correctly exposed portraits I don't see the constructive thing in saying "I don't lurk around in the dark".

If you need the high ISO, then go for the K100. Or get a deal on
the *ist D, it is still a very fine camera, and prices will get
better.

That's basically not a bad advice. But, it would be worth reading only if we discussed noise. Now it is about flaws.

What is the real meaning with your two replies?

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Jonas

mutleybird Senior Member • Posts: 1,095
Everybody here should call Pentax and explain

the issue to them.

Ater that, tell us what they said exactly.

Larry

River0 Regular Member • Posts: 308
Gordon HAS mentioned horizontal pattern noise

Actually Gordon has mentioned the horizontal pattern noise (HPN) problem:

http://forums.dpreview.com/forums/read.asp?forum=1036&message=22172171

http://forums.dpreview.com/forums/read.asp?forum=1036&message=22357087

Paul

Dave Santora wrote:

I think this is the first time I have seem any horizontal banding

  • Even GordonBGood has not mentioned this

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