[leonine]

Hello everyone,

I will be doing some night aerial photography using a Helicopter on an Asian city. I need all the light that I can grab. I have a Pentax K1 and am hoping to get Pentax K3 iii through a friend coming from US in next two weeks.

I have the Pentax A 50mm f1.2 lying with the friend in US (who doesn't do photography). I am getting a good deal on a brand new Pentax FA 50mm f1.4 at USD 200.

Can someone please share the results of these lenses wide open and focused at infinity? That will help me a lot in making a decision about whether I need to buy a new lens.

I was thinking of buying the Sony A7 iii (for its excellent with the Sigma 35mm f1.2 as a last resort. But I have heard so much about the HIGH ISO performance of the K3 iii, that I thought of saving the money and efforts in investing into a completely new camera system.

This is a once in a lifetime opportunity. I would be thankful to get actionable advice from the members.

Thank you.

[steephill]

The DFA* 50mm f1.4 would be much better than either of those older lenses. Edge and corner performance of the older lenses is poor wide open and the f1.2 has a distinct glow wide open. However if you have to go with one of the older lenses I would suggest the A50f1.2 stopped down to f2 and let the ISO rise, the K1 will perform well.

[zapp]

You will realize that f/2 and even f/2.8 will be quite sufficient. A colleague of mine did aerial mapping with with Canon 5d and 2/35 to map street illumination at night. Windows, lamps, … are quite bright at night. High ISO performance of K1 should outclass the 5d, so don’t go wide open in the first step.
DFA50 will offer best corner to corner sharpness if you do area based mapping. Currently your discussion is only f-stop based. Do you really need 50mm focal length? For mapping of areas, 35 mm will work better.

[Henrico]

I own the K1.2 which is optical identical with the A1.2. This lenses suffer some field curvature, in the center infinity is spot in calibrated, in the far edges the highest sharpness available is found a little before infinity. The M1.4 (optical identical with the FA1.4) shows a similar behavior.

These lenses were made for object isolation nearby wide open, they deliver enough center sharpness for that use. At infinity they are a bit soft and hazy wide open. From F2.8 this gets much better and from F4 they perform almost as good as their modern siblings.

Wide open you also can expect a lot of aberrations like coma. Although not at infinity the picture attached shows that perfectly.

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[UncleVanya]

I concur with the analysis of others so far. The 50mm f1.4 lenses from the FA and older series are very soft wide open and unsuitable for really sharp edge to edge shots wide open. The. DA* SMC 55 f1.4 is a little better but still isn’t in the same league for this type of use.

For my own use, The limited wide open performance can be used to creative effect or simply subject isolation, but that’s not what you are likely to want in this case.

The k3iii being a crop camera will make the dfa 50 mildly telephoto. Is that the right choice for this shot? I have no clue, but you should evaluate that before going up in the air. The K1 mk II might be a better choice. The Sigma 35 f1.4 is another lens to consider as this is a full frame fast lens with a wide angle of coverage and a reputation for good edge to edge sharpness. On apsc it will give you the “normal” lens field of view and on full frame a bit wider.

In any case good luck with the shoot.

[ismaelg]

It is more complicated than that but my simplistic suggestion: Whatever lens you choose, shoot at least 1 stop from wide open (~f2.8), careful focus at infinity and crank up the ISO as needed like there is no tomorrow.
It is easier to deal with noise in PP than "wide open lens softness"

Thanks,

[tuco]

I say tonal scale is often more important than noise. Cranking up the ISO gets you low dynamic range and poor tonal scale. Pick your poison.

[leonine]

The DFA* 50mm f1.4 would be much better than either of those older lenses. Edge and corner performance of the older lenses is poor wide open and the f1.2 has a distinct glow wide open. However if you have to go with one of the older lenses I would suggest the A50f1.2 stopped down to f2 and let the ISO rise, the K1 will perform well.

Hi,

I have the K1 and I tried it last time with FA 77mm wide open at f1.8. ISO at 6400. The results I got with shutter speeds as low as 1/90 sec with the expert pilot trying his best to reduce the vibration to the absolute minimum. The IBIS worked well. The images were sharp. But the light intensity of the city is pretty low (not like say NYC or Tokyo or London etc) and the images were not as well exposed as I would have liked. And the big city lights had horrendous purple blobs around them. Maybe the modern HD coatings of the new DFA 77mm would help control that. The old FA 77mm is absolutely superb during daylight, but looks like it can't handle so much contrast as in the city lights.

Ideally a f1.2 lens will give me one stop more light. That would certainly help. But I understand that the old lenses are quite soft wide open. So maybe stopping down to f1.4 or f1.8 would help. But the purple blobs would still be there in my opinion.

So maybe the DFA* 50mm is a good via media if used on the K3 iii. Of course it will have an effective field of view of 75mm, but I am OK with it. I can manage to move the chopper around to get the angle and field of view that I need. I don't know if the Sigma 35mm f1.4 is as good as the Pentax DFA* 50mm f1.4. If it is, its field of view at around 52mm on the K3 iii will be better for me than that of the DFA* 50mm. And I really need to do something about those big purple blobs around point sources of light.

---------- Post added 05-23-21 at 11:16 AM ----------

You will realize that f/2 and even f/2.8 will be quite sufficient. A colleague of mine did aerial mapping with with Canon 5d and 2/35 to map street illumination at night. Windows, lamps, … are quite bright at night. High ISO performance of K1 should outclass the 5d, so don’t go wide open in the first step.
DFA50 will offer best corner to corner sharpness if you do area based mapping. Currently your discussion is only f-stop based. Do you really need 50mm focal length? For mapping of areas, 35 mm will work better.

As I said earlier, the city isn't very brightly lit. So any fast lens giving good wide open performance focused at infinity would help me. Or else, if the K3 iii does as well at ISO 12800 as does the K1 at ISO 6400, I could then be in a sweet spot with such a lens. I heard a lot of good things about the Sigma 35mm f1.2 on Sony E mount.

And I am shooting streets, monuments lit up at night etc. So a 50mm to 75mm field of view is manageable, while a 35mm field of view would be the best.

The K3 iii is supposed to surpass even the K1 ii in high ISO performance, and it would also help me in wildlife photography, which is another genre I love. Hence getting the K3 iii would be better than getting the K1 ii in my opinion.

I also thought of the Kenlab gyro. But I am not fully convinced about it for this application and getting it to Asia in the Covid times is going to be difficult.

---------- Post added 05-23-21 at 11:19 AM ----------

I own the K1.2 which is optical identical with the A1.2. This lenses suffer some field curvature, in the center infinity is spot in calibrated, in the far edges the highest sharpness available is found a little before infinity. The M1.4 (optical identical with the FA1.4) shows a similar behavior.

These lenses were made for object isolation nearby wide open, they deliver enough center sharpness for that use. At infinity they are a bit soft and hazy wide open. From F2.8 this gets much better and from F4 they perform almost as good as their modern siblings.

Wide open you also can expect a lot of aberrations like coma. Although not at infinity the picture attached shows that perfectly.

Thanks Henrico. This will help. The picture tells the story perfectly.

---------- Post added 05-23-21 at 11:28 AM ----------

I concur with the analysis of others so far. The 50mm f1.4 lenses from the FA and older series are very soft wide open and unsuitable for really sharp edge to edge shots wide open. The. DA* SMC 55 f1.4 is a little better but still isn’t in the same league for this type of use.

For my own use, The limited wide open performance can be used to creative effect or simply subject isolation, but that’s not what you are likely to want in this case.

The k3iii being a crop camera will make the dfa 50 mildly telephoto. Is that the right choice for this shot? I have no clue, but you should evaluate that before going up in the air. The K1 mk II might be a better choice. The Sigma 35 f1.4 is another lens to consider as this is a full frame fast lens with a wide angle of coverage and a reputation for good edge to edge sharpness. On apsc it will give you the “normal” lens field of view and on full frame a bit wider.

In any case good luck with the shoot.

Thanks UncleVanya for valid points as always. Due to the conflicting requirements (since you can't have it all), I am OK with FOV upto 77mm on full frame or APSC. What I need is reasonable sharpness at very large apertures, minimum lens aberrations in very high contrast lighting situations and best possible high ISO performance. If the Sigma 35mm f1.4 is almost as good as the Pentax DFA* 50mm f1.4, then I will take the Sigma. It appears that despite its large aperture, the Pentax 50mm f1.2 won't be of much use for my purpose.

---------- Post added 05-23-21 at 11:30 AM ----------

It is more complicated than that but my simplistic suggestion: Whatever lens you choose, shoot at least 1 stop from wide open (~f2.8), careful focus at infinity and crank up the ISO as needed like there is no tomorrow.
It is easier to deal with noise in PP than "wide open lens softness"

Thanks,

Thanks Ismael for the valid points.

---------- Post added 05-23-21 at 11:38 AM ----------

I say tonal scale is often more important than noise. Cranking up the ISO gets you low dynamic range and poor tonal scale. Pick your poison.

Yes indeed. For such applications like night aerial photography, there are lots of compromises to be made. You get something, but then you need to sacrifice something.

Sony A7 iii with Sigma 35 f1.2 seems the best compromise. The next maybe the Fujifilm 100s with the 80mm f1.7. But I really don't want to invest into another system. So sticking to Pentax, the K3iii with DFA* 50mm f1.4 or Sigma 35mm f1.4 seem the best compromise. This assumes that the K3iii is substantially better than the K1/ K1ii in high ISO performance.

[Just1MoreDave]

...The DA* SMC 55 f1.4 is a little better but still isn’t in the same league for this type of use.

The AF is probably too slow for shots from a moving vehicle - I know this is true for my copy. It's not bad to manually focus.

[mikesbike]

The K3 iii is supposed to surpass even the K1 ii in high ISO performance,

This has not been proven in images. As you are in an airborne moving vehicle, you will need substantial shutter speed for clarity in your shot, so you will need higher ISO regardless. Any of the vintage lenses can produce green or purple fringing in high contrast situations. I have often used the FA 77mm for night shots, or just after sunset with fine results. Just lucky, I guess. But with a 50mm lens on your K-1, you will get much more in your shot than with the FA 77m lens. The "F" or "FA" 50mm f/1.7 is pretty good wide open and yet better at f/2, better-performing than the FA 50mm f/1.4 at these larger apertures. You might even consider a DA 40mm lens wide open, if available. You can of course run test shots at night when on the ground.

[kiwi_jono]

It may not be helpful but I have A 50 f1.2 and the FA 50 f1.4 and from my experience these lenses are not their best wide open and infinity and better focusing wide open on subjects say < 10m.
However that said my A 50 f1.2 seems to be say a stop better than FA 50 over the range of f1.4 - f4. By that I mean if I stop down the A 50 to f1.4 the IQ is more like the FA 50 at f2 (and in fact I quite often use the A 50 at f1.4 when I'm looking for better sharpness). Still probably not enough for you at infinity though.

[UncleVanya]

This has not been shown.

Photons to photos does show a dynamic range advantage for the k3iii over the k-1ii the difference is at iso 12800 about a half stop. The k-1ii is about 1 full stop better than the k-1 at that same iso. This isn’t consistent across the board and at base iso the k-1 models outperform the k3iii. Put another way. At iso 12800 the k3iii should perform like the original k-1 set to iso 4000 or so as far as dynamic range is concerned.

With that in mind a 1.5 stop gain in dynamic range is very nice but the iso may still need to go up farther to get the shot.

[Andrea K]

f/1,2 and f/1,4 lenses from the past era aren't built to have sharpness wide open... above all in the borders

[pinholecam]

I gave it a quick try yesterday night with my FA50/1.4 (have the K50/1.2, but did not try it ).
Assumed the settings TAv mode, 1/250, f1.4
The so called infinity for my lens wasn't even acceptably sharp (it may vary copy to copy; but I would say don't assume what you have is better (best to try it beforehand ) )
ISO was something like 20K on that setting (can be 12K if exposure -ve compensating for the shadows )
f2 is probably acceptable for smaller images and infinity focus seems correct.
f2.8 and ISO was a bit too high imho vs f2 (so the lens got sharper, but the grain went up to a point that I feel ended up to be worse )

Remember, I am assuming 1/250 and not compensating for shadows.
If you do both (eg. -1ev, 1/125, you get back 2 stops which can go to f-stop and/or ISO )

[Sandy Hancock]

If sharpness wide open is important (and I guess in this situation it is), the Sigma 35/1.4 Art or the DFA* 50/1.4 will suit you perfectly.

The Sigma is much cheaper, as well as giving you a wider field of view.

I also have both the FA 50/1.4 and A 50/1.2, and neither would be my choice for this assignment. Softness wide open, relatively poor edges, and chromatic aberration are all significant minuses.