Auto iris on or off?

[BrawlingBigJim]

I read in another post that it is best best to have the auto iris off. Why is this so? and what are the reasons? I have a Panasonic PT-AE2000U. Thanks

 

[mtrycrafts]

I read in another post that it is best best to have the auto iris off. Why is this so? and what are the reasons? I have a Panasonic PT-AE2000U. Thanks

It may give better contrast for some, so it would seem. I prefer the auto mode myself.

 

[BMXTRIX]

Auto iris can be distracting on many projectors. The shifing of the iris is typically visible, and often has a motor noise that is associated with it.

So, the 'general' recommendation is to leave it off.

But, don't confuse that with 'LEAVE IT OFF!' as a hardline law. Instead, you should really just try both modes and see which one you are most happy and satisfied with. Often times people will love what a reviewer didn't like, and in that case, it is perfect for you, and your situation.

 

[BrawlingBigJim]

I haven't noticed any noise from the iris, so that is a non-issue. What should I looking for to notice the iris shift visibly. Thanks

 

[Audioholics]

With some projectors, Epson's new lines for example, the auto iris is the only way you will get the darkest black output. With these you pretty much have to use it. The best scenario are those projectors which provide an Auto mode and also a way to set a fixed iris setting.

 

[MDS]

The concept behind this type of 'feature' is to analyze the ambient lighting conditions and adjust the iris for the best black level. LCDs and Plasmas have the same kind of feature which of course goes by different names between different brands.

For example, my Toshiba LCD has 'DynaLight'. It tries to analyze the ambient light and adust the level of the backlight on the fly. The issue is that some people may notice the slightly different black levels as they change on the fly and that is what leads to generic recommendations like 'always leave it off'.

For what it's worth, I have it on and think it works well enough. I don't notice radical changes from second to second and to my eyes the black level is pretty good. So, as usual, the best advice is to try it and make your own determination. You have to live with it on vs off for a period of time to truly determine if *you* think it is worthwhile or not.

 

[BrawlingBigJim]

Thanks for the info guys! Your knowledge is overwhelmingly fantastic! (Is that actually a word) Anyhow, I have decided to leave it on for now as I can't really see a difference either way.

 

[Audioholics]

The concept behind this type of 'feature' is to analyze the ambient lighting conditions and adjust the iris for the best black level.

That particular feature is typically connected with an automatic gamma control (given various names by manufacturers). An auto-iris is typically tied to the on-screen video content as read (ahead) by the projector's video processor. This is also why it's only really successful in products with the horsepower to do it quickly.

 

[MDS]

That particular feature is typically connected with an automatic gamma control (given various names by manufacturers). An auto-iris is typically tied to the on-screen video content as read (ahead) by the projector's video processor. This is also why it's only really successful in products with the horsepower to do it quickly.

...and the purpose is the same - to improve perceived black levels. But apparently BigBrawlingJim thought your explanation of how it is implemented means that my description of its purpose deserved negative rep.

 

[AcuDefTechGuy]

So let me get this straight.

The Auto Iris is suppose to improve the "blacker than black"?

In other words, even in dark scenes, you can see things?

So instead of being pitch black and you can't see anything but a black picture, the scene (now with Iris Open) looks grey?

 

[Seth=L]

So let me get this straight.

The Auto Iris is suppose to improve the "blacker than black"?

In other words, even in dark scenes, you can see things?

So instead of being pitch black and you can't see anything but a black picture, the scene (now with Iris Open) looks grey?

I hate grey, which is why I am so impressed with Samsung's new 850 series LCDs.

 

[AcuDefTechGuy]

I hate grey...

Same here. I hate grey. I like my blacks to be blacks even if that means I can't see everything - which is the case in real life.

That is why I don't understand the big deal with "blacker than black". Isn't that just GREY?

 

[mtrycrafts]

...
That is why I don't understand the big deal with "blacker than black". Isn't that just GREY?

There have been some interesting discussion on that at AVS, from time to time.
Blacker than black is a range on the measurement scale and in video processing for overshoots and such, almost like clipping. There is no real, usable video info in it though. Something the the mastering and processing to have a buffer, as best I know from my reading all those threads.
There is an equal space at and above 100% white side too.