pacerr,
you are totally right.
I somehow forgot I could just try different hoods.
Only problem I really ran into is that I don't have thicker paper laying around here - let alone something black. Found something orange instead.
I like the idea of just building my own hood but I have demand in regards to quality I can't fulfill with DIY.
Even making your own petal shaped hood is a great idea but like I said I wouldn't like the result unless I had the means to do it on a CNC rotary cutter...
Either I'm too stupid to find fitting stuff that is already laying around somewhere or I really don't have anything that qualifies - because I couldn't even find anything with ~77mm diameter.
Also, I prefer my Leatherman whaich also has a scissor that is actually very nifty.
newarts,
I just tested the maths-approach with my Takumar hood.
Real diameter: 60mm, theoretical minimum diameter: 55,7mm. Very close.
Trying to verify this with the same hood and the SMC Pentax 50mm F1.4 I got that the hood's diameter had to be 66mm. So either the lens isn't really F1.4 or it's longer than 50mm because the hood doesn't vignette.
But what confuses me is the Sigma's 50mm F1.4 hood. It is designed for full frame so it is too short for APS-C. Nothing new. To get the optimum hood length/depth for APS-C I just have to make it 1,54x longer.
But its shallowest part is just 28mm away from the front element.
Calculations say it could be 64mm. That's a huge difference.
Does this lens - given the fact that it is a IF design lose so much focal lengt when focusing closer? (apparently not)
Anyway, calculations say a lens hood with 77mm diameter (filter thread size) could be ~96mm deep. That's huge.
No idea what Sigma did there because testing this with a self-made paper hood shows that I can put a hood 80mm deep and some more than 70mm diameter on it and get no vignetting - at no focus distance.
So I'll probably buy this hood
Quality 77mm 77 Tele Telephoto Lens Hood Shade Metal bei eBay.de: Lens Hoods (endet 18.03.11 23:30:37 MEZ)
What would the cup be in my case?
If everything works out I'm engineer to be but I'm also a pessimist - so does this make the glass half empty and the wrong size?
Nice to see the internet is good for more than porn...