Ire, still confused.

[aebbeka]

Alright, I've read everything I can find here about ire, and I'm still not sure about myself.

I have a Sony Digital8 camera, and the black levels of the DV look fine on the computer. On the other hand, when I capture some video from VHS, that was from that same camera, using an ADVC110, it's darker. The jumper is set to the 7.5 IRE setting.

So really, I don't know what's what. From what I understand, the camera outputs 0 IRE, which is what would have been recorded onto the VHS. Then it's 7.5 IRE coming out of the VCR, thus making it darker? If this is correct, will setting the jumper to 0 IRE fix it?

Also, if all this DV video is 0 IRE, then what happens when a DVD is made and it's played on a TV? Is it correct?

Thanks!

[aebbeka]

Ok, I'll make my confusing question simpler. What I have is video from a consumer DV camera, that had been recorded to VHS. I am converting the VHS back to DV with an ADVC110. I am guessing that the camera outputted at 0 IRE, and is now being played back from a VCR too dark at 7.5 IRE. When the ADVC110 is set to 7.5, like it should be, the video appears a little on the dark side. Just now I set it to 0, and the video is lighter.

My main question is, which one is correct? Is the lighter one what it's supposed to be, or is the black simply being washed out a little? I don't have any fancy scopes, so I have included the Levels graph from Premiere for each.

ADVC110 set to 7.5 IRE - appears too dark


ADVC110 set to 0 IRE - lighter


The 0 IRE graph is what my DV video taken directly from the camera normally looks like, so it makes me want to believe it is the correct one.

Any thoughts? Thanks!

[edDV]

See if I am correctly understanding your question.

You recorded the analog NTSC output of a DV camcoder to VHS and are attempting to capture the same tape with a ADVC-110.

Here is the deal. A normal NTSC VHS tape has 7.5 IRE black and 100 IRE white. In that case you would use the ADVC-110 7.5 IRE setting to capture 7.5-100 IRE to digital levels 16-235.

Since the DV camcorder outputs 0 IRE black, the VHS deck will record that at 0 IRE. So in that case, you would set the ADVC-110 to 0 IRE. That would result in a 0-100IRE capture to digital levels 16-235.

If you had the switch in the 7.5 IRE position in that case, the ADVC-110 would map 7.5 IRE to level 16. This would cause the video in the 0-7.5 IRE range to be pushed below black (aka crushing) and would make the picture seem dark. What was 7.5 % gray would be mapped to black. All the other luminance would be shifted darker.

[aebbeka]

Yes, you understood the confusing way I asked my question exactly, and you answered exactly what I wanted to know. Thanks!

[aebbeka]

Ok, I have another clip here, and I don't have any idea what IRE setting to use. Using 7.5 makes it look too dark, and 0 makes it look a little washed out. Is there any tool or plugin out there that will give me a clue as to which one is correct? Is that what the levels graph does?

[edDV]

Ok, I have another clip here, and I don't have any idea what IRE setting to use. Using 7.5 makes it look too dark, and 0 makes it look a little washed out. Is there any tool or plugin out there that will give me a clue as to which one is correct? Is that what the levels graph does?

What is the source of the clip? Crushed blacks can't be fixed with a levels filter, washout can.

I don't have Premiere on this machine but here are a set of Vegas test scopes that show a typical capture off a cable box. This particular frame has black a bit low and maximum white around 95%.

The histogram is similar to the Premiere levels display. Note how blacks map to 16 and whites to ~235. The area below black (purple) is from bits of edge blanking that get captured at 720 (vs 704) width. If the black end of the levels seem pegged down to zero at the 7.5 IRE setting, that may indicate the source has zero IRE black.

[aebbeka]

Does the Panasonic AG-1980 output 0 IRE, despite it being made for the US?

I have old VHS tapes with stuff recorded from a Sony Video8 camera, and having the ADVC110 set on 0 instead of 7.5 looks much more correct, and so does the Levels display.

[edDV]

Does the Panasonic AG-1980 output 0 IRE, despite it being made for the US?

I have old VHS tapes with stuff recorded from a Sony Video8 camera, and having the ADVC110 set on 0 instead of 7.5 looks much more correct, and so does the Levels display.

You are in the USA. If the tapes were recorded off air then black is 7.5 IRE. If not describe the tapes in detail. Camcorder tapes could be either depending whether you bought that camcorder in Akihabara (Tokyo) or Tiawan. If you got the USA international warranty, it was most probably set to 7.5 IRE.

[aebbeka]

I'm sure the camera's black is 7.5 IRE, as it was purchased in the US. I don't know where the AG1980 originally came from, but the label on it mentions US patents, so it must be American as well.

Despite this, when playing the tapes with the AG1980, capturing as 0 IRE looks more correct. Capturing as 7.5 IRE pegs the black out at 0 on the Levels display. This is what led me to think the VCR ouputs 0 IRE no matter what the source, and because the tapes look fine (i.e. not too dark) when played on a normal VCR, I'm sure they are 7.5 IRE. This can't be though, because it should be the north american spec of 7.5!

Perhaps my videos are just supposed to be ridiculously black, but playing them back from a regular VCR and the Levels display in Premiere begs to differ...

[edDV]

I'm sure the camera's black is 7.5 IRE, as it was purchased in the US. I don't know where the AG1980 originally came from, but the label on it mentions US patents, so it must be American as well.

Despite this, when playing the tapes with the AG1980, capturing as 0 IRE looks more correct. Capturing as 7.5 IRE pegs the black out at 0 on the Levels display. This is what led me to think the VCR ouputs 0 IRE no matter what the source, and because the tapes look fine (i.e. not too dark) when played on a normal VCR, I'm sure they are 7.5 IRE. This can't be though, because it should be the north american spec of 7.5!

Perhaps my videos are just supposed to be ridiculously black, but playing them back from a regular VCR and the Levels display in Premiere begs to differ...

There are so many variables here. To narrow the issues you need to detail how this tape was recorded and on what equipment? There were alot of crap cable boxes and VCR in the past. This is more a restoration topic.

[edDV]

I'm sure the camera's black is 7.5 IRE, as it was purchased in the US. I don't know where the AG1980 originally came from, but the label on it mentions US patents, so it must be American as well.

Most likely it is NTSC standard. Make sure the monitor "bightness" is calibrated to a color bar from a pro recorded tape.
http://www.indianapolisfilm.net/article.php?story=20040117004721902

[aebbeka]

Ok, you're right. I don't know why I didn't think of this before. What I did was play back some of my footage captured at 7.5 IRE, to a regular TV through the Canopus, and then switch to the same footage playing back from a regular VCR directly to the TV. Brightness was exactly the same. Plus, the brightness on my computer monitor was in fact too low.

So, my thinking it was too dark was a combination of my monitor's brigtness, and not thinking of using a TV. This still doesn't explain why the levels display look's like this:


When captured at 0 IRE, there's a lot more to the levels display, and it's shifted over to 15, where it's supposed to be... I guess it's just a bad source. It's home videos from a Video8 camera, recorded in SLP mode on an 80's 2-head VCR, 20 years ago.

[guber]

Hi all. I know this is an old thread but I'm new here and just getting into this, so my questions are many. I've read all the posts I could find about 7.5 IRE setup, and I watched the online tutorial by JVC, and still
I find it quite hard to grasp. There just seems to be so many variables. Here is my own setup and maybe someone can shed some light for me...

I have a Panasonic AG-1980 connected (with S-video) to a new Sony dvd recorder (RDR-GX350... Best Buy model) for capturing onto DVD-R. I watch everything on a SD CRT TV.

The Sony has an option to adjust the "black level" to "on" or "off". "On" is recommended for normal use, and "off" makes the blacks crushed, so I guess that means "on" makes the setting 7.5 IRE?
The thing is, I dont know if this setting only affects the playback image of a disc, or if it also affects how a disc is recorded...any idea? If it only affects the playback, fine, but how can I tell whether the Sony records at 0 or 7.5 IRE?

I also am not sure what IRE the AG-1980 plays/records at. I didnt see any switch to adjust it. Any clue?

In addition to this setup, I will sometimes be moving the AG-1980 over to my computer, where I'll be connecting (S-video) to a Canopus ADVC-300 and capturing (Firewire) into my computer for digital editing. I currently have the ADVC-300 set to 7.5 IRE... so will that guarantee any captures from the AG-1980 will have correct black levels?

If these questions can be answered, then my ultimate question is, do I have things setup in the right way for correct black level in my DVD recordings... analog to digital capture... and playback on my TV?

Thanks in advance for the help!

[edDV]

Hi all. I know this is an old thread but I'm new here and just getting into this, so my questions are many. I've read all the posts I could find about 7.5 IRE setup, and I watched the online tutorial by JVC, and still
I find it quite hard to grasp. There just seems to be so many variables. Here is my own setup and maybe someone can shed some light for me...

I have a Panasonic AG-1980 connected (with S-video) to a new Sony dvd recorder (RDR-GX350... Best Buy model) for capturing onto DVD-R. I watch everything on a SD CRT TV.

The Sony has an option to adjust the "black level" to "on" or "off". "On" is recommended for normal use, and "off" makes the blacks crushed, so I guess that means "on" makes the setting 7.5 IRE?

Seems like "on" assumes 7.5 IRE black (digital level 16) has been recorded and "off" assumes 15 IRE black (digital level 32) has been recorded.
(see the JVC tutorial) http://pro.jvc.com/pro/attributes/prodv/clips/blacksetup/JVC_DEMO.swf

The thing is, I dont know if this setting only affects the playback image of a disc, or if it also affects how a disc is recorded...any idea? If it only affects the playback, fine, but how can I tell whether the Sony records at 0 or 7.5 IRE?

7.5 IRE black normally records to luminance digital level 16. Equipment that assumes black at 0.0 IRE will record 7.5IRE black input to digital level 32 (wash out). The switch I assume corrects the output so it plays digital level 32 to 7.5 IRE.

To be sure the SONY is recording properly, record the color bar from the ADVC (7.5 IRE switch position) to a DVD, then extract the MPeg2 to the Vegas or Premiere timeline and inspect with the scopes. The DV format timeline should be showing black at 0% and white at 100% on the waveform monitor.

I also am not sure what IRE the AG-1980 plays/records at. I didnt see any switch to adjust it. Any clue?

The AG-1980 is an analog recorder so it wouldn't have the external switch. If it is the USA NTSC model it will be assuming 7.5 IRE black in and output 7.5 IRE black. If it is a PAL or Japanese NTSC model, it will be assuming 0.0 IRE in and will output 0.0 IRE.

In addition to this setup, I will sometimes be moving the AG-1980 over to my computer, where I'll be connecting (S-video) to a Canopus ADVC-300 and capturing (Firewire) into my computer for digital editing. I currently have the ADVC-300 set to 7.5 IRE... so will that guarantee any captures from the AG-1980 will have correct black levels?

If these questions can be answered, then my ultimate question is, do I have things setup in the right way for correct black level in my DVD recordings... analog to digital capture... and playback on my TV?

Thanks in advance for the help!

The 7.5 IRE position is correct for a normal analog NTSC source. That switch position also switches the ADVC to output digital level 16 black to analog 7.5 IRE and sets the analog color bar to 7.5IRE black.

[guber]

Well, i currently have a GoDVD device (model CT-200) hooked up to the Sony recorder, and it has a color bar setting. I recorded that onto dvd with the Sony recorder, then captured a jpeg into Final Cut Pro. It read at proper IRE levels, with black at 0, white at 100.... but what I'm wondering is if there is a way to know if the GoDVD device uses 7.5 IRE in the first place?

[kimco52]

A good explanation of what SMPTE bars are and what they do and how to use them seems to be in order. This article should help explain the difference between your computer monitor and a real video monitor and why they are different plus explain how to correctly set up your color monitor to display NTSC correctly:
http://www.videouniversity.com/tvbars2.htm

Additional explanations are here:
http://www.videouniversity.com/engineer.htm

A discussion on problems with editing programs and cameras is here:
http://www.dvinfo.net/conf/showthread.php?t=106723

Standard NTSC video should have black at 7.5, nothing below 7.5. If you move it to 0, you will lose detail at the low levels. White should be at 100. Faces and flesh should be 50-80. When looking at levels from TV programs, do not look at Soap Operas. They seem to all be shaded on the dark side. Look at your local news anchors and other live shows. You will normally see them putting the faces at about 65-75.

The problem with most consumer type camcorders is that everything is on auto and some have some basic settings like sand, artificial light, normal sun, etc., and that will normally work but in low light, ???? Some may allow you to adjust some characteristics manually, but if looking at an LCD screen that is not set up correctly, you may not manually adjust things correctly, either.

Just dubbing may also present problems. That is why I always use a TBC when copying tape to tape. It allows me to manually adjust video and black gain plus compensate for color levels and phase. Except when dubbing digitally via Firewire. Then, I may adjust within Premiere if needed. One critical thing I look for in camera before I purchase one is if I can manually or automatically do white balance adjustments. When doing a multicamera shoot where I need to switch between them in edit, I need to balance the cameras before the shoot and match them in the editor before I start. That is the hard part, even between the same model numbers.