Purple blotches on Leaf Aptus 75S files.

[jing q]

moved

[Morgan_Moore]

I'm getting purple blotches on my files shot in tungsten lighting. I tried 200 ISO and 400 ISO. appears on both settings. This was shot tethered.
I'm attaching the file. I upped the exposure by 0.5 on the brightness scale in Leaf Capture 11. Is there a fix for this? It happened a month ago when I was testing it  (direct to CF card) and seemingly went away, and today it came back again.Seems pretty serious

I also had a problem where the top half of the image is purple and bottom half is green, when shot in sunlight with strobe fill, 100 ISO
Is there a fix for this problem?
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It looks like anouther enderexposed image subjected to a boost of unrealistic expectations.

excluding the computer screen there are no levels above 160 ish.


Lets look at the process,

The chip is 50 ISO deisgn.

Market forces require 'fast' backs

So leaf allow a setting of 400 ISO, 1/8th of the light the chip is designed for

They then build some amplification into the hardware to allow this

You then boost the exposure by another half stop in the software

So we are now on about 1/10th of the light required by the original design

you now balance the tungsten light to kill the yellow

this probably requires a boost in the blue channel by about a stop

so now the blue channel only has 1/20th of the light of the original design

And it goes funky - no suprise to me.

----
This is my personal rating of cameras I have used
Sinar advertised 200 my rating 50
D200/D2x, advertised 1600 my rating 100
And the D3 advertised 25000 I am reckoning is may be usable at 800
----

In terms of the colour shift - it sounds like something to do with a white reference or whatever leaf call it

Have you been playing with a view cam and not put the (software) settings back ?

S

[jing q]

urm
ISO 200 reveals this problem too.
Is there a reason for the random blotchiness.
I've shot a H2D at 400 before and didn't have this problem, just noise.

It looks like anouther enderexposed image.

excluding the computer screen there are no levels above 160 ish.
Lets look at the process,

The chip is 50 ISO deisgn.

Market forces require 'fast' backs

So leaf allow a setting of 400 ISO, 1/8th of the light the chip is designed for

They then build some amplification into the hardware to allow this

You then boost the exposure by another half stop in the software

So we are now on about 1/10th of the light required by the original design

you now balance the tungsten light to kill the yellow

this probably requires a boost in the blue channel by about a stop

so now the blue channel only has 1/20th of the light of the original design

And it goes funky - no suprise to me.

----
This is my personal rating of cameras I have used
Sinar advertised 200 my rating 50
D200/D2x, advertised 1600 my rating 100
And the D3 advertised 25000 I am reckoning is may be usable at 800
----

In terms of the colour shift - it sounds like something to do with a white reference or whatever leaf call it

Have you been playing with a view cam and not put the (software) settings back ?

S
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[Morgan_Moore]

urm
ISO 200 reveals this problem too.
Is there a reason for the random blotchiness.
I've shot a H2D at 400 before and didn't have this problem, just noise.
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Well different companies will be making different compromises in how they amplify data by a factor of 20 times

Some will go for noise others blotches

Take and image at 400, that is exposed with a few clipped highlights

Add an S curve making the darks darker - this is a typical processing curve I believe that one would use to give contrast to files on a sunny day

And show me some blotches

if there are any then send the back back

It is my opinion that high ISO is a con
the 22mp series of chips are 25 ISO
the bigger chips are 50 ISO
You can under expose from those values by a stop, or two maybe

The reason I shoot my 54LV at 50 not 25 is to give me a safety margin to stop me blowing the highlights

I think my opinions on shooting digital were forged on the D1 which certainly needed ETTR - well actually it needed using as a bookend - its current use - if you have come from slide (under = lovely and saturated) it is a shock

S

[Jonathan Wienke]

I'm getting purple blotches on my files shot in tungsten lighting. I tried 200 ISO and 400 ISO. appears on both settings. This was shot tethered.
I'm attaching the file. I upped the exposure by 0.5 on the brightness scale in Leaf Capture 11. Is there a fix for this? It happened a month ago when I was testing it  (direct to CF card) and seemingly went away, and today it came back again.Seems pretty serious

Is there a fix for this problem?

Yes, it's called "expose to the right". When shooting at higher ISO, you should never have to use a positive exposure setting in the RAW converter because when you do, you will have issues with increased noise and objectionable image artifacts such as the ones you're complaining about. You need to increase exposure in-camera, so that the RAW converter exposure setting is zero or better yet, a negative amount.

Post the RAW file; I bet if you look at it with that RAW analyzer you'll discover you can safely increase exposure a stop or two, and when you do so, your noise/blotch problem will go away.

[Rick_Allen]

I think your Firewire cable is dead, well not completely dead. You could also play with the grain adjustment in LC11 and be sure to check clean long exposure.

[jing q]

Thanks I'll check my Firewire cable.

Thread moved

[jing q]

moved and reposted at http://luminous-landscape.com/forum/index....showtopic=21191
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[pixjohn]

Have you tried shooting the white disc and using the gain adjuster?