Yeah, that might be the best idea, I will do some searching in a little while and see if I can find something that stands out from the pack, kinda doubt it but never know.
Ok, after looking through the listings it really seems to come down to location and price.
This one is nice since it is a US seller and possibly even a US made filter (doubt it) if you look at the case in the background of the picture:
http://www.ebay.com/itm/191907139332
They also have a 10% discount if you buy 2 of them. You can simply stack 2 of them to get an ND16 filter, I think this is the easiest way to allow people to measure higher powered lights vs swapping filters.
For the smaller filters there is not nearly as many options and you have to go to china to get something reasonably priced and that we can all order the same thing from. This is what I am looking at for that:
http://www.ebay.com/itm/260395103859
Only issue with this is will people want to wait for the smaller one to show up just to see if it works better vs using the one from the US seller?
I am of the opinion that since we are not measuring the lumens based on math anyways but by a calibration point. The light absorbed by the filter ring would be a non-issue since it would simply be figured into the calibration multiplier. It should be a constant percentage of light absorbed by it and as such should not cause any issues with the readings. In fact it should extend the range a bit.
Opinions?
Camera filters are truly a get-what-you-pay for experience. Going cheap is more likely to introduce as many problems as it solves. Tiffen would be good enough quality, B+W would be better. B+W uses brass rings with a threaded retaining ring, the lens can be removed. They have a chart (somewhere) that shows what size the glass is inside the filter ring. I’ll see if I can find it…
Edit: At 37mm prices aren’t horrible, wait til you need 77mm… what virtually all my “L” lenses require.
While I agree for picture quality filter price does play a big role, that is also an entirely different field and not really comparable in IMHO.
In our case we only care that they reduce the light transmittance evenly across all the filters purchased. Which should not be a problem if we all buy from the same supplier.
We do not care about clarity, color rendition (well not enough to matter), distortion or any of these other factors that play havoc on cameras.
Also the reviews on amazon for the cheap china ND filters were surprisingly good, which leads me to think that the lens is of reasonable quality. An ND filter is really one of the simplest filters to make, particularly when you do not care about the distortion/clarity.
While my good nikon uses good lenses and filters I have a few cheap lenses and a cannon that I use as a beater when I don’t want to risk the nikon. The cheap filters and lenses on it are only noticeable if you really examine a picture closely. I do not see a light meter knowing the difference personally.
I welcome suggestions if people disagree though.
My hope was that anyone that did buy the lens could use the same multiplier as someone that did not and just mathematically adjust. Ideally. And 52mm sounds big to me.
You could have this one for $4.99 and free 2-day shipping.
That is in theory true, but like anything there is always some variance. A quality lens may vary 1-2% batch to batch while a cheap one varies 5% for example. Close enough for most things but to get a truly exact match either a calibration per lens would be needed (and pretty simple to do) or get them all from the same batch.
That lens would work fine but it is an add-on item. It can only be purchased if you have another $25 in the cart and free shipping is only for orders over $49. Amazon is basically a non-option anymore due to this unless you find an individual seller that offers free shipping. Sad because I used to always shop amazon first.
This would work, these were actually what caught my eye first:
But the listing says there are only 5 available. It is even a brand name and as such would be pretty consistent.
For us Prime customers everything is free 2-day shipping. And it’s Prime-Day today, so non-members can do a Free 30-day trial and find $25 worth of other deals for their cart.
Yeah, prime members have the amazon option but I simply don’t order enough to make prime worth it, been saving the 30 day trial for the Christmas buying season myself. I am sure I am not alone in being without a prime membership which is why I tend to reject amazon out of hand when recommending things to others.
If we are not going to worry about everyone ordering the same filter then that makes things a lot simpler, everyone can pick out their own option and supplier. We simply need to standardize the size.
If 37mm is the size then once we get one in to measure any others should easily fit a bracket since the threads should be the same between them.
With this filter going in front of the meter, the quality should not really be a factor.
In front of the flashlight, like TK’s, and cheap one’s melt.
Indeed, a good filter will use glass instead of polycarbonate and would be needed if the filter were going in front of the inlet hole instead of in front of the meter.
I guess we just have different opinions on shopping. I would not pay 3.79 from Hong Kong and maybe wait until August when Amazon has it today for 4.99. And $20 more on my order is pretty easy for me.
I would agree, which is why I was wondering if it was worth the wait for the smaller filter. Although in my case trying to find another $20 to fill the cart is no small task and then another $25 to get free shipping is basically impossible. Money is too tight to buy random stuff just to get another item. To each their own though, there was a time when money was not so tight that I saw things a bit different.
Options are good, I am by no means the final opinion. If everyone else wants to go with the amazon order then that is what we can do.
Or do we just pick the size and everyone find their own filter to suite?
I’m talking about the inside hole of the meter hole. If you split the sphere in half, and look at the meter hole, it is 1 1/2 inch in diameter.
If we made that hole to 4 inch diameter, we would be able to read almost every size light including large bezeled ones like pop can and multi emitter tube lights.
So instead of using the sphere as a full circle, use as half circle.
And since the inside of the sphere is now concave, I think the 4 inch diffuser lens can be placed right over the meter hole that we just cut to 4 inches, and just shine our lights against the diffuser lens. At first, It wont seem like the lens would completely cover the meter hole, because the lens is flat. But since the hole is concaved, it should cover it fine.
This is just a thought,
This is an idea although if we split the sphere it will no longer be an “integrating” sphere. We could do this but we would lose the ability to use the nice isolation box it comes with. Plus the idea as I am sure you know with the sphere is to get an even distribution of light to the meter so the beam profile does not effect the readings.
By putting the diffuser over the meter and shining the light into the sphere like normal we still have a full integrating sphere in that the beam profile will not effect the reading but the light will be diffused enough that we can read more powerful lights.
Now opening up the hole for the flashlight to shine through is an idea worth considering as that would indeed allow for a much wider range of lights to be used.
Honestly the sphere works great as it sits, there is no reason to change the design IMO. The only issue it has is the ~1000 lumen measurement limit inside the sphere.
If we simply reduce the light getting to the meter by a fixed amount (in the case of the ND8, we allow 1/8 of the light to the meter) then we greatly increase the measurement range of the sphere and make it far more useful.
The key is realizing that we are NOT dealing with a mathematically calibrated sphere like you would find in a lab. We are dealing with a standard calibrated sphere.
The difference is that any imperfections in the design will be calibrated out when figuring out the multiplier in our case.
I agree. This sphere is done well and would hate to not use the nice box it came in and would like to keep it as a integrating sphere as a whole. I wish we can soon figure out a a way to measure out lights with much bigger heads because half of my collection depends on it.
I forget the reason why we couldn’t just make the light hole bigger? I think it was because it required a much bigger sphere and having a 3-4 inch diameter hole in our current sphere size would give inaccurate readings?
I wonder how off it would actually be?
Yes, by the math a larger hole would cause the readings to be imperfect. Although this assumes you are building a mathematically calibrated sphere. If you are, then it is important to keep the hole to sphere size correct.
Since we are using a standard calibrated sphere this is a much smaller problem IMHO. In fact I would argue that with the diffuser Josh put into the sphere to keep direct light from hitting the meter and the genius idea of putting reflective tape on the flashlight sizing rings to mimic a constant size reflector, that a larger sized hole would be not cause any issues for consistency.
As long as the sphere is consistent across the measurement range that is all that matters. You simply adjust the multiplier to make it match your standard for calibration.
That said at this point it would be pretty hard to enlarge the hole and keep the spheres standardized. It would be real hard for everyone to cut the same exact size holes.
Cool idea. Thanks Joshk.
The main consideration for the hole size limit was how big we could go on a 12” sphere and not ruin simple linearity, plus we have the thru-wall solution if you use the app’s method instead of a simple multiplier. We all thought it was a safe compromise.
To demonstrate how hard it is to accommodate all with a hole, my Dad and I both have Menards 6v lantern battery flashlights that only put out about 100 lumen, but have a 6” head.
Our goal with this project was to deliver a cheap, universal sphere. With no hard feelings if you want to mod it.
Yep and you delivered on your goal quite nicely. I see no reason to change the design of the sphere beyond a diffuser to allow for a larger measurement range.
For larger head lights you could build a PVC sphere and use this sphere to calibrate it, this is what I plan to do.
Just catching up once again. On the diffuser, it should be standardized like the sphere: One specific type from one specific seller, preferably easy on the budget (China). Those wanting it faster can pay for that. Amazon may not be good for international buyers and like Ebay the sellers come and go so next year may not find the same diffuser. The ND8 should extend the range as far as the casual user needs so I’d prefer it. And I think direct caulked-in mounting would be OK. You’d have to do something similar to mount the adapter anyway so the less complex the better.
Of course folks can experiment if they want to, but the initial idea was to have a sphere which give readings common to it’s brethren. When we’re using different parts that cannot happen. I’d like to see one single diffuser and source recommended then let the folks who have the spheres vote it up or down
Phil