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02-18-2021, 02:25 PM   #16
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QuoteOriginally posted by stevebrot Quote
When the 18-35 gets back from repair (?!) do check FOV against the FA 35 at 2 meters and closer. Most internal focus lenses have significant focus breathing at the long end with loss of working distance if used for portraits and closeups.


Steve
I did a quick FOV test, and they are so close that it is insignificant. Focus breathing on the other hand...the Sigma wins by a mile. I could not detect any in the Sigma (again, I am a novice, but to my eye there was none), but the FA35 had a very noticeable change in FOV when focusing. For me it wouldn't matter, as I had never thought to check any of my lenses for it, but now I know.

In the interest of fully educating myself, I will keep the FA35 for a bit and move my other lenses first. I'll put it in the back of the shelf, and if it ends up covered in dust I will sell it. I have the kit lenses that I no longer need either (and they ARE covered in dust), so I will divest myself of those first.

That will leave me with an 18-135 WR, 18-35 Art, the FA35 2.0, 43 LTD, FA50 1.4, FA* 300 and soon an 85 of some flavor (probably a Samyang).

---------- Post added 02-18-21 at 03:28 PM ----------

QuoteOriginally posted by pres589 Quote
Might as well sell the glass you aren't that interested in keeping around. Curious what 85 you plan to pick up. Think you'll get anything to fill in between the 18-35 and the 85?
I posted above, but I have the 43 LTD and the FA50 1.4 as well as the 18-135 WR. For the 85 I might go with the Samyang. I thought about getting a 77 LTD or an FA* 85, but I don't have the budget for either right now.

02-18-2021, 02:40 PM   #17
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QuoteOriginally posted by 5shot Quote
I did a quick FOV test, and they are so close that it is insignificant.
Did you test at 2 meters or closer? I probably should not have used the terms "FOV" or "Focus Breathing". Both have multiple meanings on the Web. It would simply be easier to suggest framing a portrait subject with both lenses and compare whether you get the same working distance. Chances are you will be enough closer with the Sigma to create volumetric distortion of features. OTOH, perhaps not...

The only reason I brought it up is that my Sigma 17-70/2.8-4.0 (C) shoots provides working distance more similar to a 50mm lens when doing portraits. That was a bit of a disappointment when I figured it out. That is one reason why I don't shoot portraits with the 17-70, preferring to get the FA 77/1.8 out of the bag instead.


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02-18-2021, 02:50 PM   #18
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According to OpticalLimits, both of these lenses are near the same for sharpness, I found the Sigma lens in the Canon APS-C reports. If you intend to shoot subjects with linear content- buildings, interiors, etc. the Sigma's pincushion distortion at 35mm is significant. Not so with the FA 35mm lens. Light falloff- vignetting is also quite significant wide open with the Sigma lens, not so with the FA 35mm at f/2. The Canon's APS-C sensor is slightly smaller than that of Pentax, so the vignetting might be slightly worse with that Sigma lens on Pentax.

Last edited by mikesbike; 02-18-2021 at 03:20 PM.
02-18-2021, 03:58 PM   #19
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QuoteOriginally posted by stevebrot Quote
Did you test at 2 meters or closer? I probably should not have used the terms "FOV" or "Focus Breathing". Both have multiple meanings on the Web. It would simply be easier to suggest framing a portrait subject with both lenses and compare whether you get the same working distance. Chances are you will be enough closer with the Sigma to create volumetric distortion of features. OTOH, perhaps not...

The only reason I brought it up is that my Sigma 17-70/2.8-4.0 (C) shoots provides working distance more similar to a 50mm lens when doing portraits. That was a bit of a disappointment when I figured it out. That is one reason why I don't shoot portraits with the 17-70, preferring to get the FA 77/1.8 out of the bag instead.


Steve
I did. Framing appeared to be identical with both at 2m and 1m. I'll take a look at distortion later tonight.

---------- Post added 02-18-21 at 04:59 PM ----------

QuoteOriginally posted by mikesbike Quote
According to OpticalLimits, both of these lenses are near the same for sharpness, I found the Sigma lens in the Canon APS-C reports. If you intend to shoot subjects with linear content- buildings, interiors, etc. the Sigma's pincushion distortion at 35mm is significant. Not so with the FA 35mm lens. Light falloff- vignetting is also quite significant wide open with the Sigma lens, not so with the FA 35mm at f/2. The Canon's APS-C sensor is slightly smaller than that of Pentax, so the vignetting might be slightly worse with that Sigma lens on Pentax.
Not shooting architecture, but I'll look into the distortion. Thanks.

02-18-2021, 05:25 PM   #20
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I took a pic of some graph paper, and I can barely see any Pin Cushion distortion. I ran the manual adjustment, and a -2 was all it took to get the image to match the superimposed grid in Lightroom.
02-18-2021, 05:38 PM - 1 Like   #21
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If you plan on getting an MZ-S in the future (great camera) then the aperture ring will come in handy
02-18-2021, 07:40 PM   #22
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QuoteOriginally posted by stevebrot Quote
When the 18-35 gets back from repair (?!) do check FOV against the FA 35 at 2 meters and closer. Most internal focus lenses have significant focus breathing at the long end with loss of working distance if used for portraits and closeups.


Steve
Mine was right here and you have me curious.

The 18-35 is great close up. I just informally checked mine at 35mm I framed a 3' picture with a little over and measured to 5.5' away. AOF calculator says 40mm should have give my results. I checked my 40m xs which was almost exactly 3' so the Sigma at 35mm giving me 38-40" from 5.5' shows negligible focus breathing. all discrepancies are within the accuracy of my measurements.
02-18-2021, 09:59 PM   #23
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QuoteOriginally posted by swanlefitte Quote
Mine was right here and you have me curious.

The 18-35 is great close up. I just informally checked mine at 35mm I framed a 3' picture with a little over and measured to 5.5' away. AOF calculator says 40mm should have give my results. I checked my 40m xs which was almost exactly 3' so the Sigma at 35mm giving me 38-40" from 5.5' shows negligible focus breathing. all discrepancies are within the accuracy of my measurements.
5.5' is pretty impressive. Sigma is doing some real magic under the covers in many ways with that lens. Calculated distance for a 3' object on APS-C is 4' 5.5" and my FA 35/2 focused in at 4' 8", a little on the long side.


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02-19-2021, 05:39 PM   #24
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QuoteOriginally posted by stevebrot Quote
Calculated distance for a 3' object on APS-C is 4' 5.5" and my FA 35/2 focused in at 4' 8", a little on the long side.


Steve
I laughingly wish you hadn't done that. It made me wonder how accurate my measurement was quickly standing behind a coffee table and moving the coffee table to hit my knees and using that distance. To satisfy my OCD and rid my mind of the nagging thought I had another go. This time I put the tape on the floor against the wall and the camera on the ground and lay down to see while using the floor boards to keep parallel. Then my camera strap was hiding the sensor mark and I spent time trying to figure out where it was without moving the camera. It turns out the SIgma 18-35 at 35mm will frame 3' at 4'10.5". So now I wonder if it is a true 35mm at infinity. Thankfully I don't have a football field near enough to go measure! That could lead to testing all my lenses for true FL and then mapping the breathing. Can I assume the different Pentax apsc have very close working sizes? or is the ks-2 20mp sensor just different enough to shift things >say 1%?
02-19-2021, 07:28 PM - 1 Like   #25
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QuoteOriginally posted by swanlefitte Quote
So now I wonder if it is a true 35mm at infinity. Thankfully I don't have a football field near enough to go measure! That could lead to testing all my lenses for true FL and then mapping the breathing. Can I assume the different Pentax apsc have very close working sizes? or is the ks-2 20mp sensor just different enough to shift things >say 1%?
Yes, it is good that I don't have a sports field nearby as well. As for frame size, there is some variation depending on sensor. The K-3, K-S1, K-S-2, K-70, and KP have 23.5x15.6mm while the K-30, K-50, and K-500 is 23.7x15.7mm. I did not look any further back.


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