CurtPalme.com Home Theater Forum

[macgyver655]

[DGP]

After reading this thread, now I think I understand why the set of HD10-GT17 originally came with my projector, have better focus than the HD10F set from a G90 I have.
My Marquee is a VDC 9500 Ultra from 2004. The picture looked really sharp but I was not able to get the same level of sharpness in all screen. First I checked if it was the focus on the CRT, but this was no the case. Center focus was perfect and corners focus close but not as good. For that reason I started to look for a set of HFQ-900 or HD10F from a G90. I was lucky to find a set of HD10F from a G90 from Curt. The sharpness I got with the HD10F set was definitely worse than the one I got from the GT17. Also contrast was better with the GT17 lenses. So I decided to keep using the GT17 lenses. Time after I found a set of HFQ-900 in Germany. This set focus better than the GT17, specially at the corners. It’s a lot easier to do the green geometry than with the GT17. Anyway, If I would have tested the lenses in my setup before paying for them, most likely I would not have bought them.

The reason that could explain this is the production date of each lens. The four first numbers of the serials numbers are:

HFQ-900 serial: 2002

HD10-GT17 serial: 2001

HD10F –G90 serial: 1998

The camera was on a tripod and the camera focus was fixed. Resolution 1920x1080p@60 from PS3 (no Scaler). Screen Da-Lite High Power surface. Projected size 220x123cm 16:9 format.

[dvh99]

damn now i want those hfq900 lenses too.

[Sparky015]

This is certainly a data point in favor of better revisions over time. Too bad they aren't published to show what they changed.

This just made a bunch of old lenses pretty worthless!

[Sparky015]

[DGP]

[dvh99]

he doesnt lol.
thats the only thing he doesnt have yet.

[macgyver655]

2 lenses of the same build quality and diameter, one being short throw and one being long throw.... the short throw will allow more light output and better edge focus. The magnification power changes across the surface of the lens. The more outer lens area you try to use the more difficult it is to achieve outer focus with a long throw vs short throw because of the magnification power.

This is why manufacturers have formulas. When you try to change from this formula by using more tube raster, it can be more difficult to achieve outer focus. The lens that was used for that model in production has to much focus loss as it moves away from center and the controls may not be capable of bringing the image into focus.

The formula is based on the ratio between the phosphor used and the screen width. The magnification power of the lens based off this ratio determines focal length.

Wasn't this posted somewhere before?

[Sparky015]

I believe that is posted in Tom's lens thread (I think). I definitely remember reading it.

The question is, and this was raised on other threads, if 3M changed a lens to be a shorter throw and/or improved the coatings, why didn't the model or revision change? As far as I know, the HD8s are still Rev. B., but yet they made a change to make a 2002 HD8 be better at widescreen apps than a 1996 HD8 as an example. Maybe Scott knows this? Not sure if this info was exchanged between 3M Precision Optics and VDC?

[PMH]

The Delta Digital 260 design was last generic from 3M Precision optics in the US. They are made in China now. the D240-260's are a generic lens meaning it was made to work with more than 1 customer in mind. If your looking for a rev you wont find one because your not dealing with revs but tooling combinations. the D260 had 4 tools running 4 cavities each thats 16 different housing (you only par the cavity to itself to reduce variation), the mount was 6 tools at 2 cavities for all D240,250, and 260 models. The optic tools are many, but the tool ID and Cavity are on the ejector pin which can only be seen by taking the lens apart (don't do it the j-clips never engage as good as the first time you will get decentering).

Now the plant in China does ok, but they lost all the experience of dealing with the issues when they closed the US plant.

You may see some aging on a 10 year old lens because plastics are not true solids the will move over time, but the biggest colprate will be the C element that is attached to the CRT, swap that with a new one and you should see less field curvature because that's the C's job.

BTW, my source for this information is that I was employed and engineered the lens at USPL,CPL,3MPO. I work on D78, D240-270, etc.

[macgyver655]

You guys have to look at these HD numbers as model numbers. And something with the same model number can have different specs through the years of production.

Say like a Ford Escort, Escort (HD10L) being the model number. Now through the years the Escort is being built the model name doesn't change but the build specs do. So to say an Escort built in 1995 is the same as the one built in 1985, would be incorrect. You would have to look at the year it was built and then look at the specs of those years.

So the specs on the HD10L would change over the years but the model number would remain the same. This is where the serial number or manufacturers part number would have to be used.

I'm sure if you looked up the 1292 HD10L Sony part number and the G90 HD10L Sony part number, they would be different.

Remember you can have a regular Escort or a turbo charged Escort, but they are both Escorts. Just different equipment. And you have to know how to tell the difference between the 2.

If the G90 lens has better overall focus then the 1292 lens on the same machine, I would say they most likely were able to improve the focal change across the lens, meaning there is less of a change over the lens face. This would not be attributed to the AR coating. However a better AR coating would also be an improvement in light reflections and light output.

[Sparky015]

[macgyver655]

He's talking RPTV lenses Sparky. I'm not sure I would classify them in the same category as FP.

[Curt Palme]

MAc, I get your analogy 3 posts above, but in the case of a car, you'd also be advised by the manufacturer about increased handling, horsepower, etc.

I'm just wondering if Delta REALLY put a lot of research into something that they probably didn't sell a lot of. It's also VERY interesting to see DGP's pix above. Now I need to try that as well, as everyone has always said that the 10F lenses were better than the Gt17s.

[Curt Palme]

MAc, I get your analogy 3 posts above, but in the case of a car, you'd also be advised by the manufacturer about increased handling, horsepower, etc.

I'm just wondering if Delta REALLY put a lot of research into something that they probably didn't sell a lot of. It's also VERY interesting to see DGP's pix above. Now I need to try that as well, as everyone has always said that the 10F lenses were better than the Gt17s.

[macgyver655]

[Sparky015]

To better put the car analogy, to us consumers, the model is an Escort, but within Ford, it's platform D123456789. You don't hear anyone saying Escort within Ford unless it's a sales or marketing puke.

[Sparky015]

[km987654]

It looks like the entire HD-10F shot is out of focus not just the edges. I can't believe that a G90 would produce such an image so hopefully this is just not focused as well as it might be.

[dvh99]

a bit off topic whithin this thread but i am curious what makes a lens resolve 12l/mm and another lens with the same size resolve 10l/mm.

dennis

[garyfritz]

Assuming they're not the same model of lens (?), it could be many things: lens design, quality of the optics, lens material (glass/plastic/whatever), etc.

If they're the same model of lens, then it could be the "model year" issue Mac mentioned above. And if they're from the same "model year," well, maybe the 10l/mm lens was made on a Monday???