Bringing Up Blacks From Black Clipping???

Michael H. Stevens · February 16th, 2008, 09:15 PM

Quote:

Originally Posted by Bob Grant

Regardless of how far to the right the histogram goes surely it's self evident when you hit clipping?
Start by underexposing and open the iris, the more of the graph that disappears to the right of the graph the more you are clipping. Same goes for clipping at the blacks. Remember that a completely black or completely white frame only shows as a single, thin vertical line on a histogram. Keep in mind that a histogram is a statistical plot of the population of pixel values and the old saying about statistics applies unless you take some care in how you read the results.

Bob: I'm saying my histogram is not disappearing at clipping! The histogram is not showing clipping at the same time the image does. When the last line start climbing the histogran is three lines past clipping. IF I want to use the histigram to set a clipping point I must open until the histogram starts to dissapear as you say, then back off until the right most three verticle lines have gone.

Craig Seeman · February 16th, 2008, 09:51 PM

Keep in mind the histogram is also measuring the quantity of pixels at that level. If you have only a few peaking pixels you may very well not see it at all on the histogram.

Point the camera at a large object with a major amount of pixels and you should see that last bar grow tall.

I really think the histogram is not the best toll for measuring peaks since that's not its purpose. That's what Zebras and the center numeric are for. Histogram is good for measuring contrast/latitude. I'll often use it as a second check to see if i need to tweak iris a bit for a bit better "spread" (depending on the look I'm going for).

Bob Grant · February 16th, 2008, 10:41 PM

Quote:

Originally Posted by Michael H. Stevens

Bob: I'm saying my histogram is not disappearing at clipping! The histogram is not showing clipping at the same time the image does. When the last line start climbing the histogran is three lines past clipping. IF I want to use the histigram to set a clipping point I must open until the histogram starts to dissapear as you say, then back off until the right most three verticle lines have gone.

How do you know the image is clipping?
If you're using the Vegas scopes in Studio RGB and assuming 100IRE is clipping I think you're looking at this incorrectly. There does seem to be something a bit wierd going on. I deliberately overexposed a piece of white card to the point that the camera is going into "Too Bright" alarm and the scopes in Vegas only read 95% (in ComputerRGB).

If I switch to 32bit/2.2 processing then the scopes show a 100% flat line! Really looks like Ive clipped it completely into digital oblivion.

If I add a ComputerRGB to studioRGB levels FX in the Preview window I'm back to what I had before with the scopes reading 95%.

Michael H. Stevens · February 17th, 2008, 12:23 AM

Ill post some screen shots tomorrow. If I increase exposure until the last line of the histogram appears then render that image and play it on a monitor (to remove the Vegas scopes from the equation) half my image will be gone to white. Maybe tomorrow I'll drop to 760p and connect DVRack up via firewire and compare scopes.

Leonard Levy · February 17th, 2008, 02:00 AM

Just my opinion, but I think you guys are putting way too much attention on the histogram. It just doesn't tell you that much.

I have seen that on a waveform the IRE indicator in the viewfinder was off maybe as much as 10 points. I can't remember which way but I'll look at it again tomorrow. I'll also check the zebras against a waveform.

Piotr Wozniacki · February 17th, 2008, 03:56 AM

Quote:

Originally Posted by Michael H. Stevens

Ill post some screen shots tomorrow. If I increase exposure until the last line of the histogram appears then render that image and play it on a monitor (to remove the Vegas scopes from the equation) half my image will be gone to white. Maybe tomorrow I'll drop to 760p and connect DVRack up via firewire and compare scopes.

Michael, to use firewire you must "drop" to SP (1440x1080), not 760p. The latter is still HQ, and the i.LINK is cut-off!

Valeriu Campan · February 17th, 2008, 05:52 AM

Michael,
I took the liberty to do a CC of the image you posted. Using Color Finesse in FCP I tried to open the shadows, soften the mid tones and add some saturation. I think that the sky is a bit too saturated for my liking...
I think the possibilities offered by this camera are incredible.

Randy Strome · February 17th, 2008, 07:53 AM

Hi Michael,

I think I know what is going on for you. The histogram will not reach the far right of the graph with certain PP's selected, as they are not producing any pixels of that brightness. An easy test. With your given settings, try to blow the highlights. Aim directly at a light bulb at close range so that it fills the screen. Look at the exposure meter and your histogram. Try again withh PP off. Report back.

Piotr Wozniacki · February 17th, 2008, 09:56 AM

Quote:

Originally Posted by Randy Strome

Hi Michael,

I think I know what is going on for you. The histogram will not reach the far right of the graph with certain PP's selected, as they are not producing any pixels of that brightness. An easy test. With your given settings, try to blow the highlights. Aim directly at a light bulb at close range so that it fills the screen. Look at the exposure meter and your histogram. Try again withh PP off. Report back.

Randy, that "The histogram will not reach the far right of the graph with certain PP's selected" is obvious, but - as always - provided one isn't heavily overexposing. You can drive the histogram towards the very RH end with ANY PP (with sufficient light, of course).

So, if Michael really means it that whatever he does, he NEVER sees his EX1's histogram filled at 100 (or is it really 108, the far RH end?), something is wrong with his histogram/camera. But frankly, I do not really think so; it just takes some practice to learn all the aspects of a quite complicated machine that the EX1 certainly is.

I can make my histogram behave in a quite predictable fashion, even though it took me several days to master it.

And one more thing: it's certainly more difficult to clip the whites with Cine4 engaged than it is with Cine1, not to mention STD3.

Craig Seeman · February 17th, 2008, 10:24 AM

I believe CineGamma 2 prevents peaks from going beyond 100. It's meant for "broadcast safe" shooting.

George Kroonder · February 17th, 2008, 10:47 AM

I took the liberty to grade your image to my preference and to shou how much information is still contained in the blacks. You can see the detail in the bushes as well as the guy under the porch: pinon_graded.jpg.

I can't attach images to my post (yet), so no preview... I've used 601 output levels, so it is a little 'flatter', but I like that ;)

In-camera a different PP and especially gamma setting should get you something like this from the start.

George/

Randy Strome · February 17th, 2008, 10:53 AM

Quote:

Originally Posted by Piotr Wozniacki

So, if Michael really means it that whatever he does, he NEVER sees his EX1's histogram filled at 100 (or is it really 108, the far RH end?), something is wrong with his histogram/camera.

Hi Piotr,
I do not think that is what is occurring for Michael, but maybe he can answer better. With PP2 selected, the histogram will never reach over 100. With some of Bill Raven's Cine based profiles for instance, When you are at the high side of proper exposure the histogram will start stacking up a few bars short of full right. It takes a major exposure boost (way out of poper exposure range) to blow past this barrier.

Michael H. Stevens · February 17th, 2008, 11:03 AM

Lets get a basic definition out of the way. The histogram is in a box. Is there any significance to the position of the left and right side? Are the extremities of the the box at clipping? If so then I can say my histogram never approaches the sides that I have seen. What I see as clipping as per the Zebras or the Spot meter only uses the center 70-80% of that box.

Randy Strome · February 17th, 2008, 11:12 AM

Quote:

Originally Posted by Michael H. Stevens

Lets get a basic definition out of the way. The histogram is in a box. Is there any significance to the position of the left and right side? Are the extremities of the the box at clipping? If so then I can say my histogram never approaches the sides that I have seen. What I see as clipping as per the Zebras or the Spot meter only uses the center 70-80% of that box.

Are you saying that if you set everything to manual, pp to off, gain to 18, iris to open, shutter to the lowest possible, ND filter to none, and aim at a bright light, that your histogram does not move to its extreme right?

Michael H. Stevens · February 17th, 2008, 01:13 PM

Quote:

Originally Posted by Randy Strome

Are you saying that if you set everything to manual, pp to off, gain to 18, iris to open, shutter to the lowest possible, ND filter to none, and aim at a bright light, that your histogram does not move to its extreme right?

Randy: NO. I am NOT saying that. Under the conditions you describe the histogram will go to the right but in this situation we are way past clipping.

What I am saying is the histogram is a long way from the right and not even to its maximum to the right as possible under the shooting conditions, when real clipping occurs. I am defining clipping as when the Zebras go to 108 and the spot meter goes to 100 and all white detail disappears.

IE to find the clipping point O need use Zebras or the spot meter or my eye. The histogram tells me nothing except a general indication of the dynamic range and this disappoints me.

mike

February 17th, 2008, 05:52 AM	#22
Valeriu Campan Major Player Join Date: Mar 2004 Location: Melbourne, Australia Posts: 223	Michael, I took the liberty to do a CC of the image you posted. Using Color Finesse in FCP I tried to open the shadows, soften the mid tones and add some saturation. I think that the sky is a bit too saturated for my liking... I think the possibilities offered by this camera are incredible. Attached Thumbnails

February 16th, 2008, 09:51 PM	#17
Craig Seeman Inner Circle Join Date: Feb 2004 Location: Brooklyn, NY, USA Posts: 3,841	Keep in mind the histogram is also measuring the quantity of pixels at that level. If you have only a few peaking pixels you may very well not see it at all on the histogram. Point the camera at a large object with a major amount of pixels and you should see that last bar grow tall. I really think the histogram is not the best toll for measuring peaks since that's not its purpose. That's what Zebras and the center numeric are for. Histogram is good for measuring contrast/latitude. I'll often use it as a second check to see if i need to tweak iris a bit for a bit better "spread" (depending on the look I'm going for).

February 17th, 2008, 12:23 AM	#19
Michael H. Stevens Major Player Join Date: Sep 2007 Location: Palm Desert, California Posts: 311	Ill post some screen shots tomorrow. If I increase exposure until the last line of the histogram appears then render that image and play it on a monitor (to remove the Vegas scopes from the equation) half my image will be gone to white. Maybe tomorrow I'll drop to 760p and connect DVRack up via firewire and compare scopes.

February 17th, 2008, 02:00 AM	#20
Leonard Levy Trustee Join Date: Feb 2006 Location: USA Posts: 1,684	Just my opinion, but I think you guys are putting way too much attention on the histogram. It just doesn't tell you that much. I have seen that on a waveform the IRE indicator in the viewfinder was off maybe as much as 10 points. I can't remember which way but I'll look at it again tomorrow. I'll also check the zebras against a waveform.

February 17th, 2008, 07:53 AM	#23
Randy Strome Major Player Join Date: Jan 2008 Location: Haiku, HI Posts: 203 Images: 12	Hi Michael, I think I know what is going on for you. The histogram will not reach the far right of the graph with certain PP's selected, as they are not producing any pixels of that brightness. An easy test. With your given settings, try to blow the highlights. Aim directly at a light bulb at close range so that it fills the screen. Look at the exposure meter and your histogram. Try again withh PP off. Report back.

February 17th, 2008, 10:24 AM	#25
Craig Seeman Inner Circle Join Date: Feb 2004 Location: Brooklyn, NY, USA Posts: 3,841	I believe CineGamma 2 prevents peaks from going beyond 100. It's meant for "broadcast safe" shooting.

February 17th, 2008, 10:47 AM	#26
George Kroonder Major Player Join Date: Jan 2008 Location: Utrecht, NL \| Europe 3rd Rock from the Sun Posts: 612	I took the liberty to grade your image to my preference and to shou how much information is still contained in the blacks. You can see the detail in the bushes as well as the guy under the porch: pinon_graded.jpg. I can't attach images to my post (yet), so no preview... I've used 601 output levels, so it is a little 'flatter', but I like that ;) In-camera a different PP and especially gamma setting should get you something like this from the start. George/

February 17th, 2008, 11:03 AM	#28
Michael H. Stevens Major Player Join Date: Sep 2007 Location: Palm Desert, California Posts: 311	Lets get a basic definition out of the way. The histogram is in a box. Is there any significance to the position of the left and right side? Are the extremities of the the box at clipping? If so then I can say my histogram never approaches the sides that I have seen. What I see as clipping as per the Zebras or the Spot meter only uses the center 70-80% of that box.