# Focal length and aperture relationship quotes

### Aperture in Photography Defined | B&H Explora

Put most simply – Aperture is 'the opening in the lens. . your subject is the main focal point and that other elements in the shot are not distracting. . Introduction to Aperture in Digital Photography Reply With Quote + Reply to and relationship between ISO, Aperture and Shutter Speed to obtain a good image's exposure. Reply to thread Reply with quote Complain f/stop is calculated (simply) as focal length divided by aperture diameter; so for example a mm. The "aperture" is the diameter of the entrance pupil of the lens, and is measures in mm. The "f-stop" is the ratio of the focal length and the.

Digital crop factor, in this way, is not going to exhibit the same image if you were to merely crop a full frame image in post as the physical measurements will actually alter the depth of field, altering the appearance of the image, depending on the DOF, all other elements being equal.

• Aperture and focal length relationship?
• Introduction to Aperture in Photography
• Understanding Depth of Field - It's Not All About Aperture

However, if you were shooting so that everything was in focus for instance think a distant landscape shotand cropped into a full frame image file to replicate the digital crop factor, the two images would appear the same barring resolution disputes, etc as if you would have shot it at the same focal length, but recorded on a smaller format.

I say this, because the angle of view, when altered by way of crop factor when used on different sensor sizes, cannot be directly replicated when using the same focal length. At this point, because the physical focal length is the variable, it will affect the DOF by increasing it for the smaller format, and decreasing it in relation by way of the larger format. Very simply, the larger the aperture, the more light allowed through the lens, the faster the shutter speed and the shallower the depth of field.

### Aperture and focal length relationship?: Beginners Questions Forum: Digital Photography Review

The light let through a lens, any lens, at a stated aperture will allow for the same shutter speed if all other exposure elements are equal. Exposure differences on digital cameras can be equated with incorrect listings on exposure variables on different cameras or formats, wherein the amplification is incongruous with the listings via other formats i.

For all intents and purposes, you should be able to essentially use one camera to meter for another camera I use a 5D2 to meter for my meter less medium format Hasselblad cm film camera all the time as exposure is exposure and if there are sample differences, it is down to the translation by a particular camera and its processor, of the physical makeup of a lens, not the numbers.

There may be firmware or processing variables, jpeg compression, etc, that could affect the way the final image is rendered, but the exposure will be the same. If you have your metering set up differently, and attempt to adjust the exposure manually based on what your light meter shows, you may come up with differing exposure settings based on how, and what your camera may be metering, but this is beside the point.

## Understanding Exposure, Part 2: Aperture

For all intents and purposes, they should register and expose light near identically numerically speaking. Even if aberration is minimized by using the best lenses, diffraction creates some spreading of the rays causing defocus.

Light falloff is also sensitive to f-stop. Many wide-angle lenses will show a significant light falloff vignetting at the edges for large apertures.

Treating the eye as an ordinary air-filled camera and lens results in a different focal length, thus yielding an incorrect f-number. Toxic substances and poisons like atropine can significantly reduce the range of aperture.

Pharmaceutical products such as eye drops may also cause similar side-effects. Tropicamide and phenylephrine are used in medicine as mydriatics to dilate pupils for retinal and lens examination. These medications take effect in about 30—45 minutes after instillation and last for about 8 hours.

Atropine is also used in such a way but its effects can last up to 2 weeks, along with the mydriatic effect; it produces cycloplegia a condition in which the crystalline lens of the eye cannot accommodate to focus near objects. This effect goes away after 8 hours. Other medications offer the contrary effect. Such drops are used in certain glaucoma patients to prevent acute glaucoma attacks. In astronomy, the f-number is commonly referred to as the focal ratio or f-ratio notated as N.