Although a few 135mms may not cover 4X5, 135 is though the standard lens for 4X5. Some folks like a 150 as they feel a 150 is sharper in the corners. I generaly use a 135mm APO for 8X10 and 11X14 and a 162 for 5X7. If you have the variable condenser head the upper condenser goes in the top rack when using a 135mm lens and is removed when a 150 or longer lens is used. If you are on a budget both Wollensack Raptars and Kodak Enlarging Extars are decent lens for very little money.