Cal Posted February 24, 2015 Share Posted February 24, 2015 Hi there.Having a bit of trouble with a focus issue and wondering if anyone can help? I notice a few of these posts cropping up on google but no answers.Anyway...after a tonne of reading and test video watching I ditched my low end Canon and bought a GH4 with EF flavoured Speedbooster, and got myself a Sigma 18-35mm 1.8. I love this thing for video, set it up with a Cine V custom profile based on Andrew's Ebook with a few changes, and have been really impressed with what I'm getting out of a cheap "video" camera.However, I can't seem to take a sharp photo if my life depended on it. I reckon I'm one in five on a good day.I'm not a photographer, should get that out the way first, and while I used to get nice stuff out of my Canon it was more to do with the wonders of RAW than skill on location. But they were always sharp.With the GH4 combo I'll be on a shoot and the video looks great. I need to get stills for web promo stuff so I flick it over to one of the photo modes (usually aperture priority but even tried on full auto when desperate), check my focus using peaking assist (the same ones I get my video in focus with every time) and snap the pic. And it goes horribly wrong. Sometimes will look sharp enough on the LCD but put it on a computer and it's way off. And a lot of the time it will look way off even on the GH4 LCD.Any ideas?? Driving me a little nuts.Know the lens doesn't have stabilisation but mainly shooting off sticks, and haven't had issue with the same lens on my old camera. So, thinking it's most likely a speedbooster thing, but as I don't have any M43 native lenses the GH4 can't clear its name either. Thanks a lot. Quote Link to comment Share on other sites More sharing options...
Nick Hughes Posted February 24, 2015 Share Posted February 24, 2015 Could be a lot of different things happening. If your videos are looking nice and sharp, then I don't think that there are any issues going on with the glass. Perhaps your shutter speed is getting set too low. I usually try not to shoot photos at anything below 1/125, or faster for longer focal lengths. Some people can get good shots with slower speeds, but I like to play it safe. Try shooting in Manual and see if that helps at all. Use the LVF if you aren't already. I would also advise against using focus peaking alone on the 18-35. I can get good results with an 85 and longer using just focus peaking, but don't recommend it for wider lenses. Try zooming in (Fn.3 by default) and see if you can nail the focus that way. Personally, I try to avoid shooting stills with MF only lenses. There are some decent options for native MFT prime lenses between $200 and $500 that would work well for photos and have decently quick AF. A good zoom would be more expensive. Quote Link to comment Share on other sites More sharing options...
nahua Posted February 24, 2015 Share Posted February 24, 2015 Get yourself a Panasonic 20mm pancake. It's not really cheap, but it's so small that you can swap out the lens quick and take awesome sharp photos. Like Nick said, shooting photos wide open and trying to use focus peaking will not mean sharp photos. Trust me, the 20mm is a winner and it's just so small, fast AF, sharp photos. Quote Link to comment Share on other sites More sharing options...
Nikkor Posted February 24, 2015 Share Posted February 24, 2015 Post sample photos with exif data so I can tell you what you are doing wrong. Quote Link to comment Share on other sites More sharing options...
AaronChicago Posted February 24, 2015 Share Posted February 24, 2015 Do you have the Speedbooster wide open? I know if you have it turned all the way to 0 the edges are really soft. Quote Link to comment Share on other sites More sharing options...
Cal Posted February 24, 2015 Author Share Posted February 24, 2015 Thanks a lot for the help.The shutter does vary as you'd expect but doesn't seem slow.I've experimented with different apertures with similar results. Don't think I have any manual controls on the Speedbooster? The thing that bugs me, which I probably didn't explain well, is that the whole image isn't soft - it's like my focal length has moved (often fairly drastically) from what it looks to my eye and confirmed rightly or wrong by the peaking. So a car I thought was sharp is soft and a sign 3 metres behind it now looks in focus.The other thing I didn't mention is that the picture are often very under exposed too. Not always but maybe 50% of the time.I'll try and dig out a photo which I haven't deleted in shame and upload!Thanks for the lens advice. My only hesitation there is most of my stuff is doco style and with little to no setup, often no lighting etc. So to carry and change out a lens would be a pretty big hassle. Quote Link to comment Share on other sites More sharing options...
leeys Posted February 24, 2015 Share Posted February 24, 2015 Peaking is not accurate. Check with the magnification assist instead.Exposure problems, what metering mode are you using, and what situations are you getting improper exposure? Matrix/evaluative metering is not 100%, and it can be fooled in certain situations. Quote Link to comment Share on other sites More sharing options...
Nick Hughes Posted February 24, 2015 Share Posted February 24, 2015 Also, make sure "Constant preview" is enabled. That will make sure that you exposure you see on screen will match the actual photo once you take it. Quote Link to comment Share on other sites More sharing options...
Cal Posted February 24, 2015 Author Share Posted February 24, 2015 Been trying for the last 15 mins to recreate the problem. And you guessed it, I can't! Everything behaving perfectly.Point taken re the peaking reliability but the focus is out by metres, not just a little soft.Constant preview is on - but yes, that's the issue I suppose - the image looks nothing like what I see on the LCD or viewfinder.I'm using the default metering mode. Think it's called Multiple. Just reading about those now and I think there's certainly room for improvement there on my part, changing to a more selective option to get that closer rather than just lifting where need be in post.But yeah, it's the crazy focus that's the main problem. I have another shoot on Friday so will try and either sort it out or post my further failings!Thanks again, really appreciate the advice. Quote Link to comment Share on other sites More sharing options...
leeys Posted February 24, 2015 Share Posted February 24, 2015 Hmm, could you have accidentally nudged the focus ring as you were taking a shot? If it looks fine in the viewfinder and suddenly it's not in the image something quite significant has changed. Quote Link to comment Share on other sites More sharing options...
Cal Posted February 24, 2015 Author Share Posted February 24, 2015 Hmm, could you have accidentally nudged the focus ring as you were taking a shot? If it looks fine in the viewfinder and suddenly it's not in the image something quite significant has changed.If I'm bumping something, then I'm doing it an awful lot!The annoying thing is that it's happened a few times now but I can never seem to recreate the issue back at home. Quote Link to comment Share on other sites More sharing options...
Cal Posted February 24, 2015 Author Share Posted February 24, 2015 Coincidence? Maybe...http://photo.net/digital-camera-forum/00d2Dt Quote Link to comment Share on other sites More sharing options...
leeys Posted February 24, 2015 Share Posted February 24, 2015 Hmm! This is an interesting issue. I wonder what could it be. Erratic aperture controls? Something causes the lens to AF on its own suddenly? If you recreate it let us know the steps involved. Quote Link to comment Share on other sites More sharing options...
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