p.8 #1 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
AGeoJO wrote:
Thank you for reminding me, both of you! Yes, my mindset is based on AF-C .
Ironically, just a few months ago some folks complained about that particular feature for studio shooting with studio strobes, I meant the feature that lets the camera focus to wide open when acquiring focus but actually taking picture at the set aperture.
Studio shooters usually complain about the inverse case - the camera focusing stopped-down instead of wide-open, which makes AF much more difficult due to the lower light levels reaching the AF system.
p.8 #2 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
snapsy wrote:
Studio shooters usually complain about the inverse case - the camera focusing stopped-down instead of wide-open, which makes AF much more difficult due to the lower light levels reaching the AF system.
Adam, that's exactly what I meant and if it doesn't come across that way, I blame it on the mobile device i used to type my post .
p.8 #3 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
It’s why I sold my GM 85 1.4 before the latest firmware update. I’m still curious about the performance now under low light in the studio as it would be nice to hear about maybe compared to the 1.8. I have the 1.8 now which is very fast in the studio
p.8 #5 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
The 2nd copy I ordered from B&H over the weekend just arrived one-day early.
S01-1816810-B
Not affected
So now I have two copies, one affected and one not. I'll compare the two when I have time tomorrow. Then pack up the first copy to send back to Crutchfield.
p.8 #7 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
Thank goodness! Third copy is a charm. Received the third copy today. S01-1817445-G 01/2018. Tested 50, 70 and 105mm. F4, F5.6 and F8 using AF-S, AF-A and MF and all in focus and sharp.
p.8 #9 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
GMPhotography wrote:
I’m thinking it’s more production lines than anything else. They may have 12 lines per say that go from start to finish and maybe one line got bad parts or something or was taught the wrong process on build.
I doubt that -- the production cycle on a lens is much much less than an hour. It depends on the efficiency of the manufacture, but e.g. market leaders are in the "raw materials to finished product" in 10 minute class
10 minutes * 16h/day (2 on / 1 off) * 5 days / wk = 249,600 lenses/yr.
Given that Sony only has 5 digits of SN after you put the year in, it is pretty safe to assume there is only a single line, or multiple inefficient lines.
p.8 #11 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
I’m sure it’s nothing malice in any way but a mistake on the production line or parts that did not meet the specs. This looks to be a very popular lens in sales buy a country mile and not too mention how good it really is for a 24-105 it’s outstanding. I’m sure Sony will come to the plate and make it right. We are talking zooms here that never ever are perfect. There has been copy variance in every zoom made regardless of brand. I repair friend of mine told me once zooms are made sloppy. Interesting comment
p.8 #12 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
I think so, but what about give back the money to the customer once a lens is not well done?
Simple and quick. For sure not only for Sony but also for Nikon, Canon and the others.
p.8 #14 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
Couple of observations on my new and working replacement lens compared to both my previous nonworking lens. The new one seems much sharper regardless of focal range and aperture. Another thing is on my previous two bad copies the vignetting was so bad at 24mm that in camera correction or even lens correction in light room would not correct the dark shading I would get in corners especially the upper right corner. I had to crop the picture to get rid of it. With the new and working lens I have no dark or shaded corners at 24mm. Seems after two bad copies I received a very good copy. I will take it!
p.8 #15 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
Alex W wrote:
Couple of observations on my new and working replacement lens compared to both my previous nonworking lens. The new one seems much sharper regardless of focal range and aperture. Another thing is on my previous two bad copies the vignetting was so bad at 24mm that in camera correction or even lens correction in light room would not correct the dark shading I would get in corners especially the upper right corner. I had to crop the picture to get rid of it. With the new and working lens I have no dark or shaded corners at 24mm. Seems after two bad copies I received a very good copy. I will take it!...Show more →
It's probably unrelated. My good vs focus-shift copy have identical vignetting at 24mm. Here's a quick comp I just did:
p.8 #16 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
I've completed my initial physical comparison of the two copies. I focused my attention on the aperture area inside the lens, since the working theory is the problem might be related to that. Looking through the front element, I compared the physical appearance of the blades and its surrounding circular sleeve as they change across the entire focal length, with special attention to the movement between 70mm - 105mm (the sleeve opens up as you zoom from wide-to-tele, while the aperture increases in size). Everything seems identical to me.
I then switched to looking from the rear of the lens, comparing the appearance and relative position of the assembly as I zoom between 70mm to 105mm. Again, no noticeable difference to my eyes.
p.8 #17 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
GMPhotography wrote:
It’s why I sold my GM 85 1.4 before the latest firmware update. I’m still curious about the performance now under low light in the studio as it would be nice to hear about maybe compared to the 1.8. I have the 1.8 now which is very fast in the studio
I am still struggling with this lens in studio situations....getting mostly softer images during headshots, shooting at 5.6 6.3. Tried all different modes, eye af, small spot af, afc, afs, view on/off. Compared to my 85 1.8, it is not nailing focus...yet tack sharp in most ambient light at any f stop. Myabe its something with the flash going off somehow changing the af at the last minute?
p.8 #18 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
snapsy wrote:
I focused my attention on the aperture area inside the lens, since the working theory is the problem might be related to that.
I was wondering if they -sound- any different when you dial the aperture down from ƒ4 to ƒ8? (It seems to me that for this amount of front focus shift the elements would almost have to be moving when you change the aperture.)
p.8 #19 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
Moving on to comparing the good vs bad copies photographically, my first test was to establish whether the bad copy's "incorrect" plane of focus is @ f/4, then shifting to the correct plane once stopped down (indicative of typical SA-focus shift), or if the incorrect plane occurs stopped down, with f/4 having the "correct" plane.
The way I sought to determine this was to mount both lenses on my A7rII on a locked-down setup, focusing on my Lens Align target. I then manually focused on the target at both f/4 and f/8. After comparing the images to make sure I got focus close (which is exceedingly hard to do btw), I then examined the EXIF fields that record the physical position of the focus position. For Sony these two fields are "Focus Position 2" and "Focus Distance 2" (the latter I believe is calculated from the first). The idea here is to see if the "bad" copy's focus position @ f/4 matches the "good" copy's focus position @ f/4 - if it does, that implies an identical plane of focus, which in turn means the "correct" plane is @ f/4, with the incorrect shift occuring stopped down after that.
For both the "good" and "bad" copies, focus position was identical @ f/4. It was "140", which corresponds to an EXIF-calculated distance field of 1.52m. However at f/8 the "good" copy remained @ "221", whereas the bad copy has to shift to "141" (1.58m) to achieve the correct focus. This implies that the "correct" plane of focus for the "bad" copy is correct, and that the "incorrect" shift happens once the aperture stops down, which in turn means this is not SA-focus shift. I believe this matches Roger's observations.
One caveat though - the encoded focus position of the lens in the EXIF appears to be rounded so that the full range of positions irrespective of lens type fits between 0-255, which means there's a bit of quantization error between the analog/physical position of the focus ring/element vs the digital value encoded in the EXIF field.
p.8 #20 · 24-105mm FOCUS SHIFT survey - FINAL RESULTS
echelonphoto wrote:
I am still struggling with this lens in studio situations....getting mostly softer images during headshots, shooting at 5.6 6.3. Tried all different modes, eye af, small spot af, afc, afs, view on/off. Compared to my 85 1.8, it is not nailing focus...yet tack sharp in most ambient light at any f stop. Myabe its something with the flash going off somehow changing the af at the last minute?
Was afraid of this. You need a big modeling light it seems
.