Alpha 7 For Legacy OM Superwides

<p>I currently use mostly legacy film lenses with my EM-1 m4/3.<br>

I miss being able to use my OM 24mm and 24mm shift (plus my Tamron SP 17mm) at their intended focal lengths. I was considering investing in an A7 for mainly this purpose.<br>

I have read elsewhere that the design of the A7 sensor degrades the edge performance of such lenses. Does anyone have relevant experience?</p>

<p>Harold, it seems that legacy wide angle film lenses made for RF cameras (Nikon, Canon pre 1970, Leica, old and current, Voigtlander-Cosina) are the most difficult, due to the short distance between the rear element and the film plane (now sensor plane) and the thick (a few mm) cover glass. Wide angle SLR lenses are apparently less problematic as their retrofocus design (required to allow intermediate mirror placement) and further distance to the sensor overcome the problem of oblique ray impingement on the edge pixels to some degree. However, each lens can constitute a special case. More recent lens designs take into account the nature of the sensor (not just the case for the Sony sensor although it may be more sensitive than others) by having the rays from the back of the lens converge on the sensor closer to an ideal 90 degree angle than the case for older lenses, especially RF camera wide angle optics. I am not an optics engineer nor a seasoned user of the A7 series, but some Photo.Net members are, including Edward Ingold. You can see his comments in a former forum discussion here:</p>

<p>http://www.photo.net/digital-camera-forum/00dLqV?start=10</p>

<p>Unless someone has made tests using your OM optics, I think the best thing may be to try to borrow an A7 (and OM to E mount adapter) from a dealer or photographer in order to try your lenses on the A7. I purchased my first zoom in a long time for the A7 series (16-35mm E mount Sony) and wanted to test it in the first few days at short and long distances and at maximum aperture in daylight. A convenient stone wall allowed the former distance and tree branches at a few hundred feet served for near infinity focus. The test enabled me to discern small fuzziness in one extreme corner at close range, but within my expectations. You might find a similar test useful if specific replies to your question are not available.</p>

<p>The Olympus OM name encompasses both DSLR and micro 4/3rds formats.</p>

<p>The problem with short focus lenses on the A7 (and orther mirrorless cameras) stems from the thickness of the sensor cover glass, and the increasing angle of incidence from the lens toward the corners of the sensor. If the lens is designed for an SLR, the back focus must be long enough to clear the mirror. As a result, the angle of incidence is much less than for a short RF lens.</p>

<p>I have found that Nikon SLR lenses work about as well on the A7 (A7ii) as on a Nikon D3. The high resolution of the A7 (24 MP) brings out any problems in the lens which may not be noticed otherwise, but they do not exhibit the corner smearing like you find with a lens designed for a film Leica, for example.</p>

<p>In short, I think the OM 24mm would work fairly well, but not as well as a lens designed for the A7. If the 24 is something you use only on occasion, the OM lens may be enough. A mount adapter is a lot cheaper than a new lens. I find I use a 24 (25 Batis) quite a lot on the Sony, so performance is important. My Nikon 24mm AFD is just not sharp enough anywhere to suit me.</p>

<p>This photo was taken last week near Lake Wenatchi in Washington, after a 24" snowfall that nearly left me stranded east of Seattle.<br /> Sony A7Rii + Loxia 35 mm 1/60 @ f/8<br /> <img src="http://d6d2h4gfvy8t8.cloudfront.net/18152371-lg.jpg" alt="" width="600" height="400" /></p>

<p>As the A7 is only a possibility for you at this stage and one of your wide angle lenses is a more expensive shift type, I would reiterate my feeling that short of a specific user experience reference with your lenses on the A7 it might be best to rent or borrow the A7 model you are considering in order to get a first hand experience. </p>

<p>Harold,</p>

<p>I have the same issue as you. I'm also considering a Sony A7 for using OM wide angles. The 21mm f/3.5 works very well with the A7 (and I have one :) ).</p>

<p>Here's some good advice from A7 users on DP review using Olympus OM glass on the A7:</p>

<p>http://www.dpreview.com/forums/post/56891259</p>

<p>I've decided to purchase the A7II. I have a number of repairs/mods to have done to my film cameras and 85 rolls of 120 B&W to process and about 130 rolls of developed film to proof & edit before I can purchase the A7II. I'm afraid that if I get the A7 II now I will never get my backlog of work cleared up :) </p>

<p> </p>

<p>Thanks, everyone.<br>

It looks like it might be worth the investment in the original version. Any wide-angle use is likely to be after the winter months, so I have time to think about whether the later version is worth the expense as IS is not important for these lenses. Other use would be with macro, where I mostly use flash (have not looked into cost justification for Sony guns, not to mention additional bulk to carry). I have some very high quality lenses (Printing Nikkors) where I could get more resolution (do I need it?) from a larger sensor.<br>

Somewhere, the rear projections of these lenses have been mentioned as a physical impairment to fitting the A7 but those would be inside the adapter,</p>

<p> </p>

<p>I think that mention of rear projection issues was not related to SLR retrofocus type WA designs but to the shorter distance back focus WA RF optics, where the angle of impingement on the sensor outside pixels would be more acute. The thicker adapters of the SLR WA lenses for the A7 reproduce the greater back focus distances within the DSLR or SLR and that helps to make non RF lenses more compatible with the mirrorless camera. </p>

<p>An annoying thing I've noticed about adapters for OM lenses in other mounts that may still apply to E is that, since the lenses all have stop-down buttons, they don't bother incorporating a stop-down ring into the adapter. As a result you might be stuck holding in the DOF preview button on your lens any time you take a shot in order to get you aperture.</p>

<p>Stephen,<br>

Thanks.<br>

Not something I have come across with OM to 4/3 or Canon FD to m4/3, but something I will ask about with sellers.</p>

 

<p>I've been using a Olympus 24mm F/2.8 MC lens on the A7. Been getting some nice results, if stopped down to f/5.6 or 8. Fairly sharp right to the edges. I'm still getting the hang of focusing manually. Need more practice on that.</p><div></div>

<p>Here is another with more distant focus. The lens seems to lose a little with closer focusing.</p>

<p> </p><div></div>

<p>Thanks, Ron.<br>

That is the lens I bought for possible macro to distance stacking, the only one I never used with film. If I had any doubts you blew them away.<br>

I use almost exclusively manual focusing, having found AF lacking.</p>

<p>Ron, credos for providing relevant tests with the wide angle Olympus lens.</p>

<p>One of the problems in judging the response of a lens may be the effect of wind if the shutter speed was not short enough (as may be its possible effect on the branches and foliage in the bottom corners of the more distant photo, also bottom left of the nearer one), the extent of near to far distances (DOF) and their possible effect on the overall focus at the particular aperture chosen (left bottom in first photo, fuzzy rocks in the bottom right corner of the second). Use of a tripod is important if the shutter speed is longer than 1/250th second (even with a 24mm lens).</p>

<p>To reduce these possible effects have you thought of photographing a brick or stone wall at close or medium distances (allowing coverage of the full wall for picture edge analysis) and with both maximum and optimum apertures (f8?)? A long distance photo at near infinity setting of the lens and with tree branches or foliage at distance and in the corners is a good way to check long distance resolution uniformity across the frame.</p>

<p>My A7 camera has trouble with RF lenses where some smearing of detail occurs in the corner. Ron, is that what is occurring to the rocks in your second photo (bottom right) or are the rocks simply too close for the focus setting and aperture chosen?</p>

<p>I hope these points are useful to you and to Harold and that the SLR lenses will work well on the A7 camera. I don't want to get hung up on details, but sometimes it is important to know what are the limiting capacities of our camera system, especially for landscape and architectural shots.</p>

<p>One thing intrigues me. Is there a trick for getting an attached image to display a magnification cursor (as your open files do and that is really neat) or is that simply a part of the PNet viewing system?</p>

<p>Arthur, I probably did do some brick wall shooting when I first got the lens, but don't have those photos anymore. My experience is that the lens stopped down can be very sharp center and border, but does lose resolution in the very corners. At maximum aperture, the lens is noticeably less sharp and lower contrast, but still okay in the center. I bought it for landscape photography, so I can work around that.</p>

<p>The Great falls picture was shot at 1/200 and probably f/5.6 or f/8. The spring house picture probably does suffer from lack of DOF at the top. I was standing close to the house, so the trees at the top were quite a bit further away. </p>

<p>PNet provided the magnifier. That is a nice feature!</p>

<p>I use older OM lenses on a Sony E-Mount and I am pretty darn happy with the combination. For OM-old school, I still have a 28,2.8 , a 50,1.4 and a 135,2.8 all of which I think work really well. I also use my legacy M mount lenses including my favorite, a v1 35mm Summicron...BUT, I would add a wrinkle, I found the a7s to be a better match, especially for the short focal length rangefinder lenses. I ended up buying a used a7s and it has really been a great decision. Even though I still have to grab my 5d when I do sports ( autofocus) I have not really put the a7s down since I got it. I don't necessarily miss the additional resolution, (the a7s is only 12mp) most of the time, though I am guessing the second a job will pay for an a7rII, I will grab it. I was also really drawn to the usable high ISO and I do think the dynamic range is discernibly better than the 5d...and I REALLY like the quality of the dynamic range of the 5d. None of those are scientific measurements and I still feel like I can get better out of the a7s, but it has really let me and forced me ( be a man, focus! ) to do better work.</p>

<p>Just dropping in to say thanks for the further contributions.</p>

<p>I was trying to snag an A7 on Ebay when an A7R got in my way. I put in a bid which I expected to be left well behind but the camera will be in my hands next week.<br>

Although not my prime purpose, I want the capability to do some macro, when the need arises, and would welcome and info on TTL RC flash, to be used off the hot shoe. (I currently use 2 or 3 with my EM-1). I am also enquiring in specialist blogs.</p>

<p>The A7R arrived yesterday and I attached the OM 24mm shift today. I used the brick wall of our house, at 90 degrees and at about 45 degrees, the latter with full shift, as the subject, and in-camera review of the images is very encouraging.</p>