29
votes
Accepted
How did this note "19/65 21/90 22/130" help previous owner of this old Zenit 12XP film camera?
Those look like DIN speeds that match values on the GOST meter dial.
GOST was the Soviet film speed standard; it was on the same scale as ASA speed, but 90% the value (so GOST 360 was equivalent to ...
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21
votes
Accepted
Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
My simple diagrams to the rescue, this time stealing yours.
I segmented some zones of the apple into little squares. Each square reflects some amount of light. When the distance is one unit (whatever ...
- 22.1k
10
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How did this note "19/65 21/90 22/130" help previous owner of this old Zenit 12XP film camera?
It's just a little conversion reference for film speeds – equating German DIN standard with Soviet GOST (ГОСТ) standard.
See Table 1 in the Wikipedia article on 'Film Speed' for example film stocks.
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7
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Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
Subject distance does vary the amount of light in accordance with the inverse square law.
If you increase the subject distance by 2x it becomes 1/2 the size LxW at the image plane... .5L x .5W is .25 ...
- 12.2k
7
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Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
Another way of looking at this effect is to look at the definition of the aperture number, also known as f-number. If, for example, you have an f-number of f/2.8, that means that the diameter of the ...
6
votes
Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
For this purpose the camera is the same as a human eye. When you look at something from further away it doesn't look dimmer, it looks smaller.
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5
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Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
Light falls off with distance. Most often this falloff follows the law of the inverse square --- but not always. This law pertains to point sources thus large area lamps do not precisely follow.
As a ...
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5
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How bright should a 18% gray card be in my image when exposed correctly?
This Kodak Gray Scale, patch # 7 is an image of an 18% gray. The theory -- an object that reflects 18% of the ambient light is the middle of the photographic scale. If the camera exposure is spot-on ...
- 37.7k
5
votes
Film exposure accident.. Help!
So, you overexposed your film by 1 1/3 stops (if you're actually exposing for ASA 160, you hint at actually exposing for a slower speed). As this isn't a whole lot, there are two things you can do:
...
- 2,704
4
votes
How does long exposure work on a digital camera?
@AlanMarcus' answer is correct, but I feel it might be missing the point of the question. Or maybe I'm missing it.
I feel like the question is asking how long exposure can work on digital devices. In ...
4
votes
Accepted
Is Evaluative metering exposing the scene to 18% gray?
That statement is far too simplistic.
18% reflectivity is middle gray (neutral/average) in a print... approximately 12.5% reflectivity is average for "a typical scene."
To properly use an 18%...
- 12.2k
4
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Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
In addition to the other answers: actually, the registered brightness of an object does depend on the distance, if its perceived size is smaller than the resolution of the system. For example, more ...
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3
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Why are there Lux - EV conversion tables, and not Lux Seconds - EV conversion table?
For that formula to work Exposure Value (EV) has to first be converted to Luminance Value (LV), which is not time based per-se.
LV is the number a vintage handheld spot meter like the Pentax V gives. ...
- 12.2k
3
votes
How does long exposure work on a digital camera?
When you take a picture, the camera lens projects an image of the outside world onto the surface of a light sensitive surface. Initially a trapdoor (shutter) blocks the projected image. When you press ...
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3
votes
Is film photography characterized as having high exposure because they have low saturation?
Short answer is no... film is not characterized by "high exposure" (high key), nor by soft color. In particular, Velvia slide film is known for particularly saturated/bold colors.
There ...
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3
votes
Is film photography characterized as having high exposure because they have low saturation?
To be honest, I didn't even manage to read through to the end of the question, because it seems to be based on so many strange assumptions.
What does Hasselblad have to do with exposure specifically?
...
- 10.7k
3
votes
Accepted
Image size trade-off with exposure
So it appears that there is a 1:1 correspondence between the sensor pixels and the image pixels. Is this the same with all cameras?
Pretty much, yes. The image pipeline in the camera will always ...
- 20.5k
3
votes
My Nikon D7100 autofocus fluctuates and will not focus on distant objects
The camera does not know what you want it to focus on.
Most pictures are easy to focus correctly. Everything is roughly at the same distance. Or, for portraits, there is a big face in the foreground. ...
- 686
3
votes
Accepted
Any fix for overexposed shot JPEG Canon Rebel T3i
If Lightroom or Corel can't recover any detail then no other program is going to either.
In a jpeg white is recorded as RGB 255/255/255, so if every pixel has exactly the same numbers/values then ...
- 12.2k
2
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How bright should a 18% gray card be in my image when exposed correctly?
There's no such thing as "correct exposure." Especially when one is talking about digital photography.
As Ansel Adams demonstrated with his Zone System almost a century ago, the photographer ...
- 173k
2
votes
Accepted
Why are dedicated light meters supposed to be independent on the sensor?
My answer is based on my humble logic so some technical details may differ from the reality :)
After the sensor the amplifier is tuned on such way so if you have particular amount of light which reach ...
- 10.1k
2
votes
Is Evaluative metering exposing the scene to 18% gray?
Since the link in your question is to one of Canon's regional marketing divisions, we'll assume you're using a Canon camera with Evaluative Metering. Canon tends to oversimplify its descriptions of ...
- 173k
2
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Why are there Lux - EV conversion tables, and not Lux Seconds - EV conversion table?
See Wikipedia.
The EV is defined as: EV=log₂(N²/t) where N is the f-number and t is the exposure time. It is a dimension-less number and there is no notion of luminance here. It's like decibels for ...
- 18.3k
2
votes
Image size trade-off with exposure
In terms of exposure (light density/noise/etc) everything revolves around light/area, not light/pixel. If you have more pixels in an area it just means each gets less light, but the total remains the ...
- 12.2k
2
votes
Understanding Entrance Pupil
Your statements 1-3 are correct... without an aperture diaphragm behind the objective the objective element's diameter is the entrance pupil.
The aperture diaphragm is then (potentially) an optical/...
- 12.2k
2
votes
Accepted
Understanding Entrance Pupil
Consider this simplified diagram.
Without a diaphragm all rays that hit the front lens are used:
With a diaphragm rays that went though the rim of the lens are stopped so the effective diameter of ...
- 18.3k
2
votes
Why does the distance from light to subject affect exposure (inverse square law) while from subject to lens does not?
If the light were large enough (i.e. wall-shaped) then that distance wouldn't matter either!
So for example, if you used a large, flat light box to illuminate a small object and shot it from the side, ...
- 1,370
2
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My Nikon D7100 autofocus fluctuates and will not focus on distant objects
This might be awkward on that Tamron, because you cannot just grab the focus wheel & manually override on the fly. You must physically switch it to manual before you can change it manually, or you ...
- 21.6k
1
vote
Accepted
How is the picture (image signal), acquired by the sensor, shown in a display?
More Current provided by a certain pixel --> More white on the screen on that pixel? If it works in that way, the perceived luminance of an image will depend on the pixel area
More Current ...
- 12.2k
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