Since buying my Devere 507 I have been looking for a couple of nice enlarging lenses (at a reasonable price), although it came with a 210mm Componon on close inspection it was a bit cloudy. I have since purchased a Nikkor 135mm f5.6 from a member on here, a 240mm f5.6 Componon (a bit dusty internally and seemingly no way to mount it) from Italy and a really nice condition 180mm f5.6 Componon from France which I got at a great price of $50 delivered.

I have had a play with them all this evening (needed additional 39mm and 50mm Devere mounts which arrived today) and amazingly they all seem to cover the 5x7 negative, seemingly with little fall off.

Now to be fair, I did expect the 210mm and 180mm to cover 5x7 okay but I was amazed that the 135mm also seemed to cover the 5x7 well. I checked the corners of the enlargements as best I could with my Omega grain magnifier against the centre of the image and could see little difference between any of the lenses once focused except that there was a little difference between them with all lenses which I put down to my use of a 5x7 negative in a glassless negative holder.

I am toying with keeping the 135mm Nikkor for my 4x5 negatives and the 180mm Componon for my 5x7 negatives which would ensure that the sweet spots of each would be in use.

So, back to my question, is there any way to identify the lens coverage of an enlarging lens?