something wide and fast?

so currently ive got

18-55mm WR
35mm FA f2.0 ~ 52mm in reality (on K7)
100mm WR
50-200mm WR

the 35mm is great but its not wide enough for this application (star trails and image stacking)... 18-55mm WR needs more speed

do you think the 35mm f2.4 DA would fair well? it is 35mm on K7 right?

the Samyang 8mm FE had crossed my mind even though its F3.5

trying to keep cost down too which makes it harder...

No, 35mm is 35mm, the same factor applies to all lenses.

35mm is a standard lens on APS-C, not a wide lens, so I would suggest the SMC Pentax-DA 12-24mm f4 as the ideal wide lens.

If you want even wider the Sigma 8-16mm is pretty good too. Link

It is rectilinear rather than the FE of the Samyang and gives the widest field of view of any current DSLR lenses so I believe. It's equivalent to a 12-24mm lens on a full frame 35mm camera and for what is is it's not that pricey either.

John K

>>No, 35mm is 35mm, the same factor applies to all lenses.

But the FA is full frame and the DA not.. surely the FOV is different between these two on the K7?

unless im misunderstanding .. hence the 35mm DA suggestion.. just over a 100 quid for an extra stop over the 18-55mm.. and although not wide it should get a reasonable amount in the image

samyang 8mm FE wide and cheaper than a zoom.. but f3.5

I tried 60x 30sec exposures [with stacking] on the 18-55mm WR with ISO 400 and F4 @ 18mm on a K7 ..

I'm not sure about the balance of FOV/speed at the moment for this

more images might of helped slightly

It's as Barrie said.

Best regards

Wider isn't always better as distortion is not your friend and WA lenses will always have a degree of distortion. Also wide and fast are almost always mutually exclusive ! You don't need fast for your intended use anyway.

You are using an APS-C camera so no need to confuse yourself with what the Full Frame 35mm equivalent FoVs are. Whatever mm the lens says it is ... it is. A 35mm is a 35mm and the FoV will only appear different on a FF camera.

Check out distortion on some of the Sigma's, 24mm or 28mm. Anything around 28mm will give you far less (almost zero) distortion compared to a WA lens. There are plenty of sharp older MF 28-35mm lenses that would do a stellar job for you (sorry couldn't resist) for £50-80 you could also consider !

Given the fact that you already have an 18mm you would not win that much with a 12-24mm (I am always impressed how much more you can capture with a few mm less focal length down around 10mm. As JAK said - test the 8-16mm (the nice thing with online shopping is, you can order it, test it 2 weeks and send it back for free if you dont like it).
I first got the 10-17mm fishey from Pentax but because it was shipped damaged, I sent it back and decided to go for a corrected 8-16mm from Pentax. I knew all the disadvantages (bulb and exposed front lense, which you can easily smash against something, no possibility to mount any filters, PRICE) BUT - it is just an enjoyable lense and it gives me lots of opportunities to be creative. If you force yourself to position the camera 100% you will be surprised how little distortion you have (great also to crop a nice pano instead of endless stitching), if you tilt it, you get dramatic perspectives and if I want fishey, I can still do it in photoshop (at least a bit fisheye ). It would also nicely add the full range of focal length to the lenses you already have with no overlap to the 18-55mm.
All these features might compensate the fact, that speed is not the key asset of this lense (but so far, I never missed it)

As already stated. A good manual focus 24mm f2.8 would be an excellent start.
If you feel you really need something wider than the 18mm end of the kit lens then by all means go ahead but as you will be stacking multiple images anyway you don't really need the extra f stops. Just take more pictures for the stack.
If you really need wider then the Pentax 12-24, Sigma 10-20 and Sigma 8-16 are worth a look.

You are misunderstanding

Put you kit lens on 35 mm and take a photo. Next put the FA35 on and take the same photo. Compare the field of view; no difference.

35mm is 35mm is ... The field of view in this case (equal focal length) depends on the sensor size

A Full Frame image is 36mm x 24mm. With a 35mm lens this gives a horizontal field of view of approx 54 degrees.

An APS-C image is 23.4mm x 15.6mm (K-5, other cameras may vary slightly) i.e. the sensor is only 2/3 the size of a full frame one. So now a 35mm lens gives a smaller horizontal field of view of only approx 36 degrees.

You'll often hear the term crop factor, this refers to the equivalent focal length of a lens being used on a full frame camera. For a K-5 this factor is approx 1.5x. Therefore a 35mm lens used on an APS-C DSLR gives the same field of view as a 52.5mm lens on full frame camera.

John

I have a Sigma 10 - 20 in my bag. It's not the new faster one but is fabulous for big landscapes and seascapes or Greek temples and the like. 15mm equivalent is a very wide angle so I use it less than expected. The DA 18 - 55 lens is no slouch and is of course nice and compact.

I have a KR so can use 800 ISO with no perceptible loss of quality. A faster lens is therefore not an issue for me at wide angle. At portrait length upwards of course control of depth of field becomes fun.

The Samyang 14mm f2.8 seems like a good wide, fast lens. Although I must admit, I don't really see the point of the extra speed UWA lens. You can select lower shutter speeds before camera shake affects images, and generally UWA type shots benefit from greater depth of field.

Noticed this comparative review

https://www.pentaxforums.com/reviews/pentax-12-24mm-lens-comparison/the-bottom-l...#

Does the 15mm F4 prime come out better than these at 15mm?

Quite liking the creative shots ive seen with the Fish Eyes (the Samyang 8mm FE and the Pentax 10-17mm FE). Need to find a shot at each focal length on the pentax somewhere.