Can Someone please help with scaling to 1/25 photo or parts when you have no idea what the scale ofthe photo is.
You need a ‘landmark’ or piece of truth. It may be something as small as a lug nut. Knowing that the nut is about 3/4 (+/-) inch, measure the photo with the nut and measure the unknown part. How many nut-sizes are in the part. Now you have inches, then divide by 25 (1:25).