[knightzerox]

I'm in a bit of a dilemma and I am not sure if I made the right decision. I am heading off on a trip to Italy and have decided to take my Sigma 10-20, Pentax 18-135, and needed a indoor low-light lens. My two options were my 50 1.4 and my FA 43 1.9. Both the 50 and the 43 were too long to be useful indoors when needing to take group photos, sitting at a table on a restaurant, close focus shots etc... Otherwise, the FA43 is what I always use.

I was originally planning to get the 20-40 LTD as I have been very interested in it and it seemed like it would give me the "flexible prime" I would need and some low light performance. I had added the lens to my cart and at the last minute asked for it to be changed to the 31 mm limited as it checked all the boxes. Close focusing, larger aperture for low light, wider field of view and so on and it seemed perfect.

After receiving the lens, I'm a bit underwhelmed. It's beautiful, build quality is excellent, and images are very sharp from f 2.2 and above. But, at 1.8 it's very quirky. Sometimes it's very sharp and others, it's just barely ok. I know about AF focusing issues and have all my lenses calibrated and have been comparing it to CDAF to verify.

After getting all of it calibrated in, now the comparisons come in. I have the 35mm DAL 2.4, which is an excellent lens and is very similar to the 31 in focal length, close focusing, and sharp. What I have found is that while the FA 31 is sharper at the same apertures, it's hard to justify. The biggest reason is that I am able to get sharp clear photos at open apertures on my FA 43 but with the FA 31 it's a hit or miss at 1.8. Oddly enough, when I stop down to 2.2 or 2.4, I get that same wow factor i'm used to in really great and beautiful sharpness on the image. But if I have to stop down to 2.4, the low-light performance and IQ benefits start to wear thin as I could just use the 35 DAL 2.4. Again, the both lenses at 2.4 are sharp but the 31 is slightly sharper. I'm just not sure it's worth the $800 in cost over the 35mm DAL that I already have.

The 20-40 I had originally wanted may not be the best in lowlight either as it is usually at f4 for most of the range, but it may be more viable? I've found the 18-135 to be so good when shot appropriately at the right aperture that other than indoor lighting, I am happy with that lens.

Saying all that, I have a FA 77 coming tomorrow and will be going through this exercise again with my HD DA 70 ltd haha. There is something about the FA's that make you fall in love with them and while hard to justify, I just "feel" like I am getting better photos with a better quality lens usually. Just wish I could understand why at 1.8 it seems to be very sharp but when I shoot at a little longer distance ( 1 foot versus 2-3 feet ). it just doesn't sharpen up. I have read most users here feel that it is sharp but soft at 1.8 but after stopping down it is great and I have seen that for sure.

I'm not sure if I should return the FA 31 and just use my 35mm 2.4 or if I am expecting to much from the lens.

[Ole]

Have you considered using the 18-135 indoors and crank up the ISO a bit? I would think that 31mm (or 35mm) isn't quite wide enough for your purpose. Also, using a large aperture for shots of people at a table creates depth of field challenges, so even though the 18-135mm is kind of slow it might be the better option. If you occasionally should need the extra stop you have your 35 mm F2.4.

I think you can safely save the $800 plus unless you have some more fitting use for the 31mm.

[knightzerox]

Have you considered using the 18-135 indoors and crank up the ISO a bit? I would think that 31mm (or 35mm) isn't quite wide enough for your purpose. Also, using a large aperture for shots of people at a table creates depth of field challenges, so even though the 18-135mm is kind of slow it might be the better option. If you occasionally should need the extra stop you have your 35 mm F2.4.

I think you can safely save the $800 plus unless you have some more fitting use for the 31mm.

I have used it indoors in what would be considered low light conditions and it is acceptable to certain ISO levels. It's actually not bad at all, but, there may be cases where I want a wide FOV with shallow depth of field or need that extra low light. Of course these are just assumptions but you are right, shooting at a table with 1.8 might be too shallow regardless and I may not be able to take advantage of it. I will shoot some more today as I have a sometime to decide before I have to return the lens. I don't use the 35mm FL much thought I found it wide enough to use instead of the 43 or say a 21mm. I think it's the FL I need, just not sure it's worth the price difference. I could afford to keep all the lenses, but I feel I could divert money into a more applicable lens. If the 20-40 was full frame compatible through ti's entire range, I'd probably switch it for that.

[6BQ5]

First : Which body are you using?

Second : The lens sharpens up significantly as the aperture is stopped down. Check out the test data : Pentax smc FA 31 mm f/1.8 AL review - Image resolution - Lenstip.com

Third : I have had worse luck with CDAF than PDAF on my K-3. Sometimes I feel like the CDAF overshoots the perfect AF point because the screw drive AF motor can't stop in time. After calibrating my lenses on my K-3 I can achieve better focus which occurs at f/1.8. As Ole said above, depth of field at f/1.8 is really thin, even at 31mm, and it's easy to miss focus if the K-3 is powering through the focus range.

Fourth : Make a few portrait shots before you dismiss the FA 31mm Limited and compare the out-of-focus areas between it and the DA 35mm. Compare the colors, contrast, and general rendering. A good test of resolution is photographing something dusty. Dust is very fine and small. Many camera sensors and lenses together have a hard time resolving details as small as that.

[DeadJohn]

The Sigma 10-20 might fill your indoor low-light requirement. Wide angles are more forgiving of camera shake as long as you don't crop heavily. Shake Reduction + slow shutter + high ISO might be adequate for your low light photos.

[seventysixersfan]

After receiving the lens, I'm a bit underwhelmed. It's beautiful, build quality is excellent, and images are very sharp from f 2.2 and above. But, at 1.8 it's very quirky. Sometimes it's very sharp and others, it's just barely ok.

I'm just not sure it's worth the $800 in cost over the 35mm DAL that I already have.

Thank you for the feedback on your experiences/opinion of the lens. I have thought a lot about getting the FA 31 to replace my FA 35 but I am doubtful that the benefits gained will be worth the huge cost.

I have the DA 20-40 and it's an excellent performer. I usually shoot at the wide end (20mm) when I'm indoors, in order to get the f/2.8 aperture. The lens handles beautifully and I'm very pleased with the sharpness of the images.

[savoche]

I don't think your 31 sounds very different from mine. That said, I prefer the results from the 31 over the 35. I prefer the size of the 35, though. And is the difference worth $800? Well, if you have the money...

I still like the 43 more, but as you say it's a tad long indoors. I like the DA21 a lot for use inside. Not blazingly fast, but 3.2 is just half a stop slower than the 2.8 of the 20-40.

Another good option is an F/FA28 if the 35 should be too long and the 21 doesn't fit the bill.

Or the FA*24/2, maybe?

[knightzerox]

First : Which body are you using?

Second : The lens sharpens up significantly as the aperture is stopped down. Check out the test data : Pentax smc FA 31 mm f/1.8 AL review - Image resolution - Lenstip.com

Third : I have had worse luck with CDAF than PDAF on my K-3. Sometimes I feel like the CDAF overshoots the perfect AF point because the screw drive AF motor can't stop in time. After calibrating my lenses on my K-3 I can achieve better focus which occurs at f/1.8. As Ole said above, depth of field at f/1.8 is really thin, even at 31mm, and it's easy to miss focus if the K-3 is powering through the focus range.

Fourth : Make a few portrait shots before you dismiss the FA 31mm Limited and compare the out-of-focus areas between it and the DA 35mm. Compare the colors, contrast, and general rendering. A good test of resolution is photographing something dusty. Dust is very fine and small. Many camera sensors and lenses together have a hard time resolving details as small as that.

I'm using the K-3 which seems to be working fine and is consistent with my other lenses. I think i will need to do more tripod and real world tests again today to compare both, as if the 31 is sharper and more consistent I will keep it. I think the mis-focus point is what is bugging me, though in manual mode it's all of course perfectly fine. I 'm able to get it to AF on close subjects fine, but as the distance expands it gets worse. I may need to check my calibration again as I'll move from -6 to -2 depending on subject distance.

I've taken many portrait shots of my dog, and this is where the FA 31 has been failing me unless I shoot at 2.2+ my DA 70 and FA 43 are just fantastic here, but at 1.8 this lens just misses focus to easily I think without some further calibration. I will keep trying again as I feel that it should be fine, and I a mover analyzing, but since I have an option to return it and get something else I and scrutinizing it more. I will have to find someone other than my dog to pose for me. I have a husky and his hair is very fine and many cameras and lenses will easily blend his fur into a white blob instead of the fine -grained hairs which is why I like to photograph him. I'll post some samples later.

---------- Post added 06-04-15 at 01:40 PM ----------

The Sigma 10-20 might fill your indoor low-light requirement. Wide angles are more forgiving of camera shake as long as you don't crop heavily. Shake Reduction + slow shutter + high ISO might be adequate for your low light photos.

I agree, it might be ok but I feel the 20 mm is too wide for me a bit. I just don't shoot at that FL as often but can if I need to. Honestly, the lens is having a AF motor issue and I would get it fixed but I don't think I can get the lens repaired before m trip. I'm going to shoot it in manual mode or use the AF if I can, works half the time.

---------- Post added 06-04-15 at 01:45 PM ----------

Thank you for the feedback on your experiences/opinion of the lens. I have thought a lot about getting the FA 31 to replace my FA 35 but I am doubtful that the benefits gained will be worth the huge cost.

I have the DA 20-40 and it's an excellent performer. I usually shoot at the wide end (20mm) when I'm indoors, in order to get the f/2.8 aperture. The lens handles beautifully and I'm very pleased with the sharpness of the images.

If the lens was $600, I would keep it without thought and it would justify the higher price. Maybe even $800 at the most. I paid $996 over the weekend sale and it's around that price at some retailer still. I've heard very good things about the 20-40, and I'm tempted to purchase it as well. It would fit well where I want a flexible prime but not the full 18-135 range and need a little better low light performance. Otherwise the 18-135 is a marvelous lens. I never used it much before but once I really started to use it and see how it should be used, it's truly a amazing lens and has made compromises where they make the most sense.

---------- Post added 06-04-15 at 01:47 PM ----------

I don't think your 31 sounds very different from mine. That said, I prefer the results from the 31 over the 35. I prefer the size of the 35, though. And is the difference worth $800? Well, if you have the money...

I still like the 43 more, but as you say it's a tad long indoors. I like the DA21 a lot for use inside. Not blazingly fast, but 3.2 is just half a stop slower than the 2.8 of the 20-40.

Another good option is an F/FA28 if the 35 should be too long and the 21 doesn't fit the bill.

Or the FA*24/2, maybe?

Oh don't give me more lens choices! I may end up with the FA 31, FA 77, 20-40, and keep the HD 70 and 35 DAL. I guess it's only money in the end....

[jrpower10]

I wouldn't trade my 31 for any other lens, but truthfully I use it in manual focus more than autofocus, and usually not wide open. It'll be the last lens I part with when I'm done with DSLR's. That said, it's a very personal choice as to what's important in a lens and only you can decide.

[sungibr]

The 31mm is, with no doubt, a very expensive lens. When I bought mine, I was also intrigued by a lack of sharpness in some picture at wide open aperture. I shot with a K5II and calibrating seemed to have little effect, but using it more i kinda learn how to get wide open picture that are sharp.
Of course, the DA35 or the FA 35 are also two high quality lenses, that compete in almost same league as the 31, and cost wise, is difficult to justify the price for the limited FA, so in my opinion, the decision to one over another will be purely by personal taste.
In my kind of shooting, the bokeh, the vignettes at wide aperture and the shallow dept of field of the FA31 matches my liking, so is hard to advises to you what you can do.
The only thing I could say is think about what you want it to do for you. The answer might be another lens indeed.

[clackers]

In addition to the DA20-40, there's the Sigma 18-35mm if you want f1.8, Knightzerox.

[jonby]

Yes I was thinking of the 18-35 too. Several primes in one, but I'm guessing the OP may not appreciate the size/weight. What about the Sigma 30mm 1.4 Art? A lot cheaper than the 31 and I would guess a bit sharper at max aperture in the centre. Then there's always the Sigma 35mm 1.4 - stunning performance, full frame compatible and still cheaper than the 31. Sorry yes more choices I'm afraid!

[starjedi]

I'm in a bit of a dilemma and I am not sure if I made the right decision. I am heading off on a trip to Italy and have decided to take my Sigma 10-20, Pentax 18-135, and needed a indoor low-light lens. My two options were my 50 1.4 and my FA 43 1.9. Both the 50 and the 43 were too long to be useful indoors when needing to take group photos, sitting at a table on a restaurant, close focus shots etc... Otherwise, the FA43 is what I always use.

I was originally planning to get the 20-40 LTD as I have been very interested in it and it seemed like it would give me the "flexible prime" I would need and some low light performance. I had added the lens to my cart and at the last minute asked for it to be changed to the 31 mm limited as it checked all the boxes. Close focusing, larger aperture for low light, wider field of view and so on and it seemed perfect.

After receiving the lens, I'm a bit underwhelmed. It's beautiful, build quality is excellent, and images are very sharp from f 2.2 and above. But, at 1.8 it's very quirky. Sometimes it's very sharp and others, it's just barely ok. I know about AF focusing issues and have all my lenses calibrated and have been comparing it to CDAF to verify.

After getting all of it calibrated in, now the comparisons come in. I have the 35mm DAL 2.4, which is an excellent lens and is very similar to the 31 in focal length, close focusing, and sharp. What I have found is that while the FA 31 is sharper at the same apertures, it's hard to justify. The biggest reason is that I am able to get sharp clear photos at open apertures on my FA 43 but with the FA 31 it's a hit or miss at 1.8. Oddly enough, when I stop down to 2.2 or 2.4, I get that same wow factor i'm used to in really great and beautiful sharpness on the image. But if I have to stop down to 2.4, the low-light performance and IQ benefits start to wear thin as I could just use the 35 DAL 2.4. Again, the both lenses at 2.4 are sharp but the 31 is slightly sharper. I'm just not sure it's worth the $800 in cost over the 35mm DAL that I already have.

The 20-40 I had originally wanted may not be the best in lowlight either as it is usually at f4 for most of the range, but it may be more viable? I've found the 18-135 to be so good when shot appropriately at the right aperture that other than indoor lighting, I am happy with that lens.

Saying all that, I have a FA 77 coming tomorrow and will be going through this exercise again with my HD DA 70 ltd haha. There is something about the FA's that make you fall in love with them and while hard to justify, I just "feel" like I am getting better photos with a better quality lens usually. Just wish I could understand why at 1.8 it seems to be very sharp but when I shoot at a little longer distance ( 1 foot versus 2-3 feet ). it just doesn't sharpen up. I have read most users here feel that it is sharp but soft at 1.8 but after stopping down it is great and I have seen that for sure.

I'm not sure if I should return the FA 31 and just use my 35mm 2.4 or if I am expecting to much from the lens.

Be patient! Enjoy this legendary lens. :-)

[aleonx3]

I have the 18-135, 31, 43, 77 and the 20-40. I think it depends on your application and how you want to use them for. For me, I would pick the 18-135 and the 20-40 as a travelling lenses covering both day (outdoor) and night (indoor) activities (add the 360 II of course). I would use the trio if it is a day trip when I know I would have plenty of time to change lenses and also when I want to get some creative shots with wide-open aperture.

[Venom3300]

you have to keep in mind how old the design is...