Originally Posted by blee0120
I want to know what relationship does contrast play toward black levels. Just did some research on contrast ratios. Looked up the contrast ratios for the Epsons, Sonys, and JVCs. Some reviewers states that the Epsons and Sonys have the same or better blacks than jvc, but jvc have a better contrast. Need a little education from the knowledgeable
Sony and Epson both use a dynamic iris (DI) wihin the lens assembly of their projectors. The DI can open and close to increase or decrease the amount of light coming from the lens. During scenes in the video which are mostly dark the DI will close down and make ther overall projected image darker. This lowers the black level, but also lowers the whites and all other shades by the same amount. Such projectors have two different black levels and contrast ratios (CRs). One is the "native" values that are measured when the DI is turned off (generally with the iris locked in the full open position). The other mode used for measurements, and the only one the manufactures will use for coming up with their spec. sheets and inflated advertising claims, is with the DI engaged at its most aggressive setting. They then project a full white screen and measure the white level (the DI will automatically fully open for this signal) then they project a full black screen to measure the black level (the DI will close down to its minimum for this type of signal). This latter test will produce big numbers for the contrast ratio (CR = ratio of white level to black level) and a low value for black level. However, many users will find this most extreme setting for the DI unacceptable due to the side effects it causes. When DI is engaged a more moderate setting will generally be more acceptable for most users. The best of the sub-$5K Sony and Epson projectors have native contrast ratios in the range of 5,000:1 while Sony's flagship 1080p projecfor, model VW95es, has native
CR of 10,000:1 or a little higher. These Sony and Epson projectors can achieve a realistic dynamic
CR of perhaps 50,000:1 maximum using DI turned on and set to a moderate level so as to not produce too many objectionable side effects. However, projectors using DI simply will not produce overall results (in terms of image quality) equivalent to an otherwise similar performing projector that achieves a similar measured CR value, but does this without use of a DI (i.e, having a high native CR).
The JVC projectors do not need to rely on DI (and don't have one) as they have very high native CR and low black levels.Note that all of the above dicusssion concerns On/Off Contrast Ratios, which are the only type normally specified by the projector manufacturers.Edited by Ron Jones - 1/29/13 at 7:59am