Image-Labratory UV filter?

[Doug A]

Found them on eBay. They use special cement to bond a UV 11 and BG40 filter together. They point out one needs a UV modified camera, and modified Samsung cameras still can't record UV. Never heard that before. $200 for a 77mm filter seems reasonable. I wonder how many UV capable lenses use such large lens elements?

Thanks,

Doug A

[ulf]

I must make you disappointed Doug.

You are referring to this filter stack: https://www.ebay.com/itm/191827622437

 

First, sorry for yet another very long answer filled with facts.

I hope you can take time and read all of it and if something is not clear, please ask.

 

A stack of BG40 and UG11, when those components are typically thick like 2mm each will not surpress the secondary peak at around 700nm enough.

You get an optical density off just above 3 (OD 3).

That is a bit worse than Kolari's UV Pass filter that states > OD 3.5 ($349.99 for a 77mm filter)

 

Many years ago OD 3 was considered enough for UV photography, but a few years ago practical tests in the real world made us redefine this.

The modern Baader U have better than OD 4. I measured my Baader U-copy to around OD 4.2.

 

OD3 will give UV-photo images that some times are OK-ish, but several times will show more or less IR leakage.

Higher OD is more important with lenses that have less transmission in the UV range.

If you had an UV-Nikkor such a filter would perform better as the ratio between UV and IR would be more favourable.

 

In some very rare cases I have seen a very slight hint of IR-leakage even with that rather strong blocking of OD 4.2.

That leakage was not present in a photo of the same flower, taken just a minute later taken with a filter stack with a measured OD > 5.0.

 

The OD value is logarithmic, meaning that for every integer step there is a tenfold change in optical density.

---

Beside the rather arrogant phrasing in their adds some things stated are not true:

 

Bonding agents that are UV transparent are commonly used when designing filters and lens systems for the upper UV ranges. Not doing so would be really stupid.

However none that I am aware of is transparent all the way down to 210nm!

That might be one of the reasons you never see any cemented lens groups in lenses reaching that deep.

 

There are some other sellers that also provide measured transmission curves. For this type of filter the one provided by Image-Laboratory you need an OD graph or a logaritmic graph to make the very small remaining peak at 700nm visible. Their graph is nonsense in that aspect and you would not be able to see even an OD 2.5.

 

---

I have bought filters from Image-laboratory several times and the UG11 I got from them https://www.ebay.com/itm/196099763720 is quite OK  

 

When ordering an AR coated BG38 and specifically asked them that they should a BG38 and not a BG40 I still got a BG40. The reason for asking this time is that I had orderd a BG38 before for a less critical application and then gotten a BG40 in a box saying BG38. 

https://www.ebay.com/itm/196121992908

I could provide a correct transmission curve of BG40 measured from the filter they sent as proof of the error and still did not get a refund.

 

Here is what they write:

 

"I have 100% seller feedback and always describe my items as they are.
No surprises

Please note that some buyers do not bother to check transmission curves from manufacture's websites to see if what they buy is what they need. They rather do assumptions or read "opinions" on internet forums.
Any claims as "not as described" must be accompanied by transmission curve produced by the buyer compared to the manufacturer's transmission curve within margin of error."

 

 

[Andy Perrin]

For sure that ebay seller Image-laboratory is not very trustworthy. I believe we have had LOTS run-ins with them on the forum going back many years. 

[dabateman]

Yes I have gotten a scratched filter from them and what was labeled as UG glass was really just much cheaper ZwB glass.

 

I consider them a used chinese distributor in the US. 

Roll the dice and see if you have some luck.

[Doug A]

@ulf thanks for the technical info. Thought their claim that manufacturers aren't using proper UV cement was far fetched. I do understand the basics of OD. Hadn't made the connection between a "poorer"  lens needing higher OD. Thanks for this. 

@Andy Perrin the seller uses fairly hostile language in their ad. That was a warning sign to me. Their statement about  using the wrong white balance and blaming IR leakage is telling.

@dabateman good to know. 

 

I wasn't going to order anything from them. None of my accidental UV lenses are remotely close to 77mm. Just interested because they were a company I hadn't heard of. Perhaps this thread will remind people to be careful with poor sellers. Wonder how this company keeps a 100% rating?

 

Thanks,

Doug A

[Andy Perrin]

10 minutes ago, Doug A said:

Wonder how this company keeps a 100% rating?

Think of how many people wouldn't even realize their problems are caused by an IR leak. So long as they ship on time and the goods look like the description, most people aren't going to complain.

[Andrea B.]

Ulf writes: The modern Baader U have better than OD 4. I measured my Baader U-copy to around OD 4.2.

 

Ulf, I just searched for a recent topic which presents the OD of a Baader-U. We have some old topics (like, 2016) discussing IR leakage of a Baader-U. If you would be so kind as to write one and perhaps include the chart of your Baader-U measurement, I think it would be quite useful for searching purposes. The topic title could perhaps be "Recent Baader-U has OD 4.2" or something similar. 

 

(If your Baader-U measurement is already here somewhere, then I did not find it in my initial search.)

 

P.S.  I do not buy from Image Laboratory. 

[ulf]

I showed the Baader U transmission of my filter here in this topic:

https://www.ultravioletphotography.com/content/index.php?/topic/2992-infrared-block-broad-uv-and-visible-pass-filter/page/2/

 

Similar graphs might have come later, but are difficult to find.

Later I have learned that to make essential information relatively easy to find you have to create a separate topic with a good descriptive title.
I will search my old raw spectrum measurement data and see if I can find any better measurements to use for new graphs in a topic as the one you suggest above.

 

You and I also had a private dialogue about the Baader U that you initiated November 24, 2018. The title was "Permission request"