Mark_L Posted February 11, 2012 Share #1 Posted February 11, 2012 Advertisement (gone after registration) I am performing the test of the focussing at 2.8 at different distances to check if I need to get it adjusted. Looking at the pictures it seems it back focusses around 2m. But I also have 2m distances that worked out fine. Is it possible that there is nothing wrong, but that I miss once in a while. The Depth of Field at 2m at f2.8 is only a few centimeters still. Any one a similar experience with this lens and that it just takes more practice focussing with a 90 mm, I have been used to 35 all the time and that is going smooth. I would liket to avoid sending all to Solms of course, if needed it must happen, but I would like to be sure then. The 4982 has the back focus, focus on the first knight. The 4983 does not have it for same focus, at same distance. Link to post Share on other sites More sharing options...
Advertisement Posted February 11, 2012 Posted February 11, 2012 Hi Mark_L, Take a look here back focussing M8 and Elmarit 90. I'm sure you'll find what you were looking for!
WestMichigan Posted February 11, 2012 Share #2 Posted February 11, 2012 Query: Were you shooting from a tripod? I ask because The framing is slightly different between the two images. That alone could account for the problem just from a slight shift fore or aft in your body placement. Sincerely R in Mi Link to post Share on other sites More sharing options...
tobey bilek Posted February 11, 2012 Share #3 Posted February 11, 2012 Focusing in the center, then swinging the lens will bring the focus point forward. But I have no idea how you got the figures off center in the bottom pic. Traditional M cameras have two focus calibration points, infinity and one meter from film plane. The M digital may have 3. Further you can not tell if the problem is the lens or the camera without more lenses. Tolerence stack up can give false results which is some thing to guard against when doing home testing. Link to post Share on other sites More sharing options...
lct Posted February 11, 2012 Share #4 Posted February 11, 2012 Better keeping the subject matter on the RF patch to be sure. Also you're not very far from the limits of the M8's RF accuracy at f/2.8 so you might wish to focus bracket a bit. Link to post Share on other sites More sharing options...
Mark_L Posted February 11, 2012 Author Share #5 Posted February 11, 2012 Query: Were you shooting from a tripod?I ask because The framing is slightly different between the two images. That alone could account for the problem just from a slight shift fore or aft in your body placement. Sincerely R in Mi No I don't use a tripod, and indeed the angle must have changed a bit, distance was the same though Link to post Share on other sites More sharing options...
lct Posted February 11, 2012 Share #6 Posted February 11, 2012 Better use a tripod as well. Link to post Share on other sites More sharing options...
WestMichigan Posted February 12, 2012 Share #7 Posted February 12, 2012 Advertisement (gone after registration) Better use a tripod as well. I completely agree with and second all that lct has advised. :-) Despite how wonderful and magnificent the human body is, there is no way to shoot test sequences handheld as precisely and repeatedly as your experiment requires in order to achieve a meaningful result. The variables will simply stack up across the sequences and make a hash of the data. Sorry. Focus bracketing is advised because one of the variables you are coping with is the fact the human eyeball is not as infallible or repeatable as our brains think it might be. I believe Sean Reid has an entire article on his fine, fine website which meaningfully describes the morass of variables he has to cope with conducting the Lens Tests which are a part of the lens reviews he writes. Richard in Michigan Link to post Share on other sites More sharing options...
IWC Doppel Posted February 13, 2012 Share #8 Posted February 13, 2012 Mark, hi For what it's worth I have seemingly 'had' potential back focus with my M8 and 90mm Elmarit-M f2.8 I then (unscientifically) tested and did not find the problem as consistently. I then carefully cleaned the wheel (It had some black whiteness marks of some deposits) and then the lens with swap and alcohol. Seems much better afterwards and I no longer have any problems, I have just shots indoors at f2.8 some close 1-2m and others up to 40 foot away. Out of seven shots the speed at ISO 1250 was between 1/15th and 1/60th one was out (me) one was okay, the rest were spot on. I am not sure if I was unlucky when I first became concerned but I no longer am. Did the clean solve the issue ? Not sure ! Link to post Share on other sites More sharing options...
Mark_L Posted February 15, 2012 Author Share #9 Posted February 15, 2012 Mark, hi For what it's worth I have seemingly 'had' potential back focus with my M8 and 90mm Elmarit-M f2.8 I then (unscientifically) tested and did not find the problem as consistently.! I must say that I can't reproduce it myself anymore, which is good news, I didn't clean it but perhaps by just using it a little dirt might have been removed. It is one of the first of the latest Elmarits and it might not have been used for a long time. Anyway, this is for the better, no extra cost and no being without my camera. Thanks Mark Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.