Nikon D7500 Reference Manual - English - Page 210

Depending on the lens used and scene recorded, the in-focus indicator (I) may be displayed when the subject is not in focus, or the camera may be unable to focus and the shutter release will be disabled. In mode P, the maximum aperture (minimum f-number) is limited according to ISO sensitivity, as shown below: Maximum aperture at ISO equivalent of: 100 200 400 800 1600 3200 6400 12800 4 4.8 5.6 6.7 8 9.5 11 13 If the maximum aperture of the lens is smaller than given above, the maximum value for aperture will be the maximum aperture of the lens. Noise in the form of lines may appear in flash photographs taken with an SD-9 or SD-8A high-performance battery pack attached directly to the camera. Reduce ISO sensitivity or increase the distance between the camera and the power pack. A The AS-15 Sync Terminal Adapter When the AS-15 sync terminal adapter (available separately) is mounted on the camera accessory shoe, flash accessories can be connected via a sync terminal. D Use Only Nikon Flash Accessories Use only Nikon flash units. Negative voltages or voltages over 250 V applied to the accessory shoe could not only prevent normal operation, but damage the sync circuitry of the camera or flash. Before using a Nikon flash unit not listed in this section, contact a Nikonauthorized service representative for more information. 210 Optional Flash Units