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<blockquote data-quote="aroy" data-source="post: 317624" data-attributes="member: 16090">The amount of light transmitted in a lense is given by its &quot;T&quot;value. Aperture is a rough indicator, but ultimately it is the T value that matters. To get an idea of T values of various lenses, use DXO &quot;compare lenses&quot; facility.&nbsp;For still photography it does not matter much as the meter evaluates the light entering through the lense and adjusts the exposure accordingly. With video, things are a bit different as it is not possible to keep adjusting exposure automatically between frames. In most cases the aperture is changed manually (or with an add on device).It is important to match the transmission of different lenses to be used in a video shoot. If T values do not match the video brightness will vary across lenses. That is why lenses used for video are matched for consistent T values.If you are serious about video, it is better to get lenses which have aperture ring. In fact a lot of people prefer the older manual focus lenses for video. Nikon &quot;D&quot; lenses do not, MF and &quot;D&quot; lenses do. As Nikon cameras do not change the aperture constantly in video, your only recourse to adjust for variable light is to adjust the aperture on the fly. That is why lense for video have stepless aperture ring.</blockquote>

[QUOTE="aroy, post: 317624, member: 16090"] The amount of light transmitted in a lense is given by its "T"value. Aperture is a rough indicator, but ultimately it is the T value that matters. To get an idea of T values of various lenses, use DXO "compare lenses" facility. For still photography it does not matter much as the meter evaluates the light entering through the lense and adjusts the exposure accordingly. With video, things are a bit different as it is not possible to keep adjusting exposure automatically between frames. In most cases the aperture is changed manually (or with an add on device). It is important to match the transmission of different lenses to be used in a video shoot. If T values do not match the video brightness will vary across lenses. That is why lenses used for video are matched for consistent T values. If you are serious about video, it is better to get lenses which have aperture ring. In fact a lot of people prefer the older manual focus lenses for video. Nikon "D" lenses do not, MF and "D" lenses do. As Nikon cameras do not change the aperture constantly in video, your only recourse to adjust for variable light is to adjust the aperture on the fly. That is why lense for video have stepless aperture ring. [/QUOTE]

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