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"Leave on" UV filter
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Mar 26, 2019 16:33:26   #
E.L.. Shapiro Loc: Ottawa, Ontario Canada
 
Blenheim Orange wrote:
I was told that there should not be anything between the lens and the subject, because of the risk that the images might be distorted. I then started really noticing that there was a lot of dust in the air, and it was just about everywhere! So after that I tried to shoot only on very, very calm days, but still there was airborne dust between the lens and the subject. So I decided to move to San Francisco, where the prevailing winds came from the west across the Pacific ocean, which kept the air very clean. I would do anything for my art! Still, it was dry all summer and cars and trucks would kick up dust. Worse yet, I started noticing wavy sort of effects in the air, and was told I was seeing thermoclines, areas where there was a temperature differential and the optical properties of the air were distorted. On hot days this was especially bad. Even when I could avoid these, I ran into another problem. When shooting landscapes sometimes distant objects were fuzzy and had a blue cast. I asked other photographers about that, and they told me that there was water vapor - right in the air! - and that this caused the problem I was having.

Now I live in a nice small room with no windows. I am hoping that if I stay very, very still for a few hours, and wait for just the right time of day when the temperature has equalized through the room, that I might be able to overcome these problems. I was making plans for building a vacuum chamber in the basement when my family called the authorities and then a nice man came and he suggested moving to the small room where I now live.

Mike
I was told that there should not be anything betwe... (show quote)


Now! Here's a man with a fine sense if humor. Made my day.

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Mar 26, 2019 16:38:05   #
Blenheim Orange Loc: Michigan
 
E.L.. Shapiro wrote:
Now! Here's a man with a fine sense if humor. Made my day.



Reply
Mar 27, 2019 08:45:38   #
Silverrails
 
imagemeister wrote:
Some of us, like me, tried to tell you about this ........do keep a good HOOD in place for protection.


Yes, this is what I have read, a good lens "Hood" is adequate protection for your lens. I had a hard plastic lens hood for my 67mm 18-140 lens, somehow when at the Zoo with my Granddaughter it actually fell off my lens, without my notice immediately, did not find it where I had been, so when I got home, I ordered a 3 stage Rubber collapsible 67mm Lens hood from Amazon, got it in 2 days, hoping this one will do it's duty and stay on my lens. Does any UHH members have experience with a "Rubber" 3 stage collapsible Lens hood?

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Mar 27, 2019 14:43:11   #
DanielB Loc: San Diego, Ca
 
Einreb92 wrote:
I was told to eliminate anything between the subject and the sensor that is not necessary. I was also told to keep the hood on as it is a very good method of protecting the glass and shielding the lens from stray light rays. Just passing along what I was told and practice. Interesting bird!


I do the same - it's just extra glass in front of the lens.

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Mar 28, 2019 20:25:24   #
Bipod
 
Blenheim Orange wrote:
I was told that there should not be anything between the lens and the subject, because of the risk that the images might be distorted. I then started really noticing that there was a lot of dust in the air, and it was just about everywhere! So after that I tried to shoot only on very, very calm days, but still there was airborne dust between the lens and the subject. So I decided to move to San Francisco, where the prevailing winds came from the west across the Pacific ocean, which kept the air very clean. I would do anything for my art! Still, it was dry all summer and cars and trucks would kick up dust. Worse yet, I started noticing wavy sort of effects in the air, and was told I was seeing thermoclines, areas where there was a temperature differential and the optical properties of the air were distorted. On hot days this was especially bad. Even when I could avoid these, I ran into another problem. When shooting landscapes sometimes distant objects were fuzzy and had a blue cast. I asked other photographers about that, and they told me that there was water vapor - right in the air! - and that this caused the problem I was having.

Now I live in a nice small room with no windows. I am hoping that if I stay very, very still for a few hours, and wait for just the right time of day when the temperature has equalized through the room, that I might be able to overcome these problems. I was making plans for building a vacuum chamber in the basement when my family called the authorities and then a nice man came and he suggested moving to the small room where I now live.

Mike
I was told that there should not be anything betwe... (show quote)

The "shimmer" one sees on hot days is an exmaple of atmospheric refraction, caused by
light passing though regions of air of different density (cold air is denser). If there it's
just a layer of hotter or colder air (a thermocline), then you would see distortion. But
if the air is moving up and down due to convection, you will see shimmer.

Shimmer makes pars of the image move, which causes unsharpness. This can be lessened
somewhat by using a faster shutter speed. Some types of AF can be confused by shimmer,
so you might try manually focusing if that's feasible.

The air temperature is usually the most even in the early morning hours, befor the sun starts
to warm the ground. So that's the best to shoot to void aerial refraction.

That fuzz, hazy, bluish distance is known as "atmospheric perspective" (or "aerial perspective").
It's an important technique in landscape paiinting:

Albert Bierstadt (1830-1902), The Marina Piccola 1859, oil on canvas
https://upload.wikimedia.org/wikipedia/commons/thumb/9/94/Albert_Bierstadt_-_The_Marina_Piccola%2C_Capri.jpg/1024px-Albert_Bierstadt_-_The_Marina_Piccola%2C_Capri.jpg

The blue color is due to "Rayleigh scattering" cause by tiny water droplets in the air. Longer wavelength
are less affected, so the result is a bluish cast. UV light is the most affected, which is why a UV filter
reduces haze in cameras that are senstive to UV light.

Digital sensors have a "notch" filter on the sensor that blocks both IR and IV, and passes visible light.
However, some of these fiters pass a signficant portion of UV A. So digital cameras vary in their senstivity
to UV.

Lenses also vary in how much UV they transmit, depending mainly on the optical cement used in the
groups. Unfortunatley, few lens makers provide a transmission spectrum graph in their lens specifications.

Optical cements have changed quite a bit over the years. At one time, all lenses used Canada
balsalm (basically, tree sap), which transmits UV. Today Canada balsalm is rarely used, and formulas
basd on acrylic, silicone, or (rarely) exposy are preferred. Many modern optical cements are cured by
exposing them to UV light---genreally, these absorb UV light and transmit relatively little.

Basically, you just have to try a camera and lens on a hazy day with and without a UV filter, to see if it
make any difference. (Probably it won't, and almost certainly it won't make a big a difference as it would
on a film camera with the same lens.)

Reply
Mar 28, 2019 23:22:13   #
Blenheim Orange Loc: Michigan
 
Bipod wrote:
The "shimmer" one sees on hot days is an exmaple of atmospheric refraction, caused by
light passing though regions of air of different density (cold air is denser). If there it's
just a layer of hotter or colder air (a thermocline), then you would see distortion. But
if the air is moving up and down due to convection, you will see shimmer.

Shimmer makes pars of the image move, which causes unsharpness. This can be lessened
somewhat by using a faster shutter speed. Some types of AF can be confused by shimmer,
so you might try manually focusing if that's feasible.

The air temperature is usually the most even in the early morning hours, befor the sun starts
to warm the ground. So that's the best to shoot to void aerial refraction.

That fuzz, hazy, bluish distance is known as "atmospheric perspective" (or "aerial perspective").
It's an important technique in landscape paiinting:

Albert Bierstadt (1830-1902), The Marina Piccola 1859, oil on canvas
https://upload.wikimedia.org/wikipedia/commons/thumb/9/94/Albert_Bierstadt_-_The_Marina_Piccola%2C_Capri.jpg/1024px-Albert_Bierstadt_-_The_Marina_Piccola%2C_Capri.jpg

The blue color is due to "Rayleigh scattering" cause by tiny water droplets in the air. Longer wavelength
are less affected, so the result is a bluish cast. UV light is the most affected, which is why a UV filter
reduces haze in cameras that are senstive to UV light.

Digital sensors have a "notch" filter on the sensor that blocks both IR and IV, and passes visible light.
However, some of these fiters pass a signficant portion of UV A. So digital cameras vary in their senstivity
to UV.

Lenses also vary in how much UV they transmit, depending mainly on the optical cement used in the
groups. Unfortunatley, few lens makers provide a transmission spectrum graph in their lens specifications.

Optical cements have changed quite a bit over the years. At one time, all lenses used Canada
balsalm (basically, tree sap), which transmits UV. Today Canada balsalm is rarely used, and formulas
basd on acrylic, silicone, or (rarely) exposy are preferred. Many modern optical cements are cured by
exposing them to UV light---genreally, these absorb UV light and transmit relatively little.

Basically, you just have to try a camera and lens on a hazy day with and without a UV filter, to see if it
make any difference. (Probably it won't, and almost certainly it won't make a big a difference as it would
on a film camera with the same lens.)
The "shimmer" one sees on hot days is an... (show quote)


Understood. My post was an attempt at humor.

Mike

Reply
Mar 28, 2019 23:28:07   #
Bill_de Loc: US
 
Blenheim Orange wrote:
Understood. My post was an attempt at humor.

Mike


So, you have no padding on the walls?

---

Reply
 
 
Mar 28, 2019 23:42:32   #
Blenheim Orange Loc: Michigan
 
Bill_de wrote:
So, you have no padding on the walls?

---




I just posted on a thread titled "I keep banging my head against the wall."

https://www.uglyhedgehog.com/t-585093-1.html

Mike

Reply
Mar 29, 2019 00:04:14   #
waykee7 Loc: Cortez, Colorado
 
jerryc41 wrote:
I'm sure that's an extreme example, but there is no advantage to using a UV filter rather than a clear filter. A lens hood is also good. A Xume magnetic adapter will let have the filter on or off in less than a second.


I had bad luck with the Manfrotto magnetic filter system; apparently bumped a $100 B&W polarizer and knocked it off unknown to me, and despite backtracking for 3/4 miles, couldn't find it. The convenience is
alluring, but I'm not a fan of the system anymore.

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