[Craigbob]

All,

I currently have the FA-J 18-35 f/4-5.6, and while it's an okay lens, it can be a bit soft. I'm wondering if I gain anything by going with the Pentax FA 20-35mm F4, or if I'm just losing 2mm on the wide end for the constant f/4 aperture.

EDIT: The camera is a K-1

Has anyone compared the 2 lenses? I do have the 15-30 and while that's a sharp lens,it's a bit un-wieldy to use in an aquarium, and finding a rubber lens hood for it is a no-go. Even my Ultimate Lens Hood won't fit over it.

---

Last edited by Craigbob; 10-11-2019 at 03:01 PM. Reason: Added camera Info.

[Gerbermiester]

Between the two lenses You already own, there's not much to gain with the 20-35mm. The 20-35mm has a better optics than the 18-35mm, but both of these are rather weak wide open (which is what you'll be shooting in an aquarium, I'd assume). Either stop down the 18-35mm or shoot the with the DFA would be my advice.

[kiwi_jono]

Maybe something like Samyang 20mm might fit the bill?

[bdery]

If I had decided to purchase the 15-30, I would have known about the size and accepted it And I wouldn't use an FA-J lens in its stead, it's a vastly superior lens optically.

The FA 20-35 is fine, probably noticeably better than the FA-J, but its sharpness does not compare with the 15-30. Its rendering, especially at night, is very good though.

[mikesbike]

All,

I currentloy have the FA-J 18-35 f/4-5.6, and while it's an okay lens, it can be a bit soft. I'm wondering if I gain anything by going with the Pentax FA 20-35mm F4, or if I'm just losing 2mm on the wide end for the constant f/4 aperture.

Has anyone compared the 2 lenses? I do have the 15-30 and while that's a sharp lens,it's a bit un-wieldy to use in an aquarium, and finding a rubber lens hood for it is a no-go. Even my Ultimate Lens Hood won't fit over it.

What camera are you using? Both those lenses are for full frame bodies, being designed for 35mm film use. If you are shooting with an APS-C DSLR, and since you obviously would benefit greatly from having a fast aperture pro-style zoom lens for low light use, I highly recommend the Sigma 17-50mm f/2.8 EX DC HSM constant aperture lens which is now being offered at a non pro-style price by B&H. $358 with free shipping. A $311 savings from a reasonable original price for such a lens. I took advantage of this outstanding deal some weeks ago and I have been very impressed with this lens. I use it on both my K-5 IIs and KP bodies.

Fast, accurate, quiet AF and a very sharp lens.

[Ash]

Agree with the above. Whilst I don’t have the 15-30, I know there is nothing that compares to it in terms of image quality on a full frame camera. So leaving that one home due to size means you’re going to sacrifice image quality no matter what else you take in its stead.

So far I’ve avoided the 15-30 for a similar reason but thankfully have the FA 20 and Rokinon 14. Both of these are fast lenses but still don’t have the distortion control and colour contrast of the 15-30. But the 20 is reasonably wide, can take filters and is a very small and lightweight lens. That’s the trade off.

[Craigbob]

What camera are you using? Both those lenses are for full frame bodies, being designed for 35mm film use. If you are shooting with an APS-C DSLR, and since you obviously would benefit greatly from having a fast aperture pro-style zoom lens for low light use, I highly recommend the Sigma 17-50mm f/2.8 EX DC HSM constant aperture lens which is now being offered at a non pro-style price by B&H. $358 with free shipping. A $311 savings from a reasonable original price for such a lens. I took advantage of this outstanding deal some weeks ago and I have been very impressed with this lens. I use it on both my K-5 IIs and KP bodies.

Fast, accurate, quiet AF and a very sharp lens.

Sorry, I thought I mentioned it in the OP, I have the K-1 so both of my current lenses and the 20-35 are fine on it.

---------- Post added 10-11-19 at 03:04 PM ----------

Between the two lenses You already own, there's not much to gain with the 20-35mm. The 20-35mm has a better optics than the 18-35mm, but both of these are rather weak wide open (which is what you'll be shooting in an aquarium, I'd assume). Either stop down the 18-35mm or shoot the with the DFA would be my advice.

In my aquarium shooting I typically shoot TVA ISO AUTO (up to 8000) and shutter speeds between 1/125 and 1/250. Aperture varies from wide open to 2 stops down.

[Gerbermiester]

In my aquarium shooting I typically shoot TVA ISO AUTO (up to 8000) and shutter speeds between 1/125 and 1/250. Aperture varies from wide open to 2 stops down.

I'd keep the 18-35mm in that case if you're willing to keep the ISO's in your higher range. The IQ difference between the 20-35 and the 18-35, while present, is more or less negligible when shot indoors, handheld, with high ISO. Plus you already have the 15-30mm f/2.8!

Don't succumb to LBA!

I sold my 18-35mm about a year ago. I didn't use it past 24mm, so I opted instead for an ultra-wide prime. (The Vivitar 13mm f/2.8 which is a rebranded Samyang). This probably won't suit your needs, but I've been happy with the results for me.

[disconnekt]

Don't succumb to LBA!

To (loosely) quote a famous Star Wars chatacter

L.B.A. leads to G.A.S.
G.A.S. leads to a more money being spend
More money being spend leads to suffering (in your wallet, shelf space, and from your significant other)

😂😂

Maybe something like Samyang 20mm might fit the bill?

I was wondering something similar. Do you need a zoom lens to photograph the contents of an aquarium? I was thinking maybe the 35mm macro would work better? (Obviously, I'm assuming something about the size of the aquarium.)

[mikesbike]

Sorry, I thought I mentioned it in the OP, I have the K-1 so both of my current lenses and the 20-35 are fine on it.

---------- Post added 10-11-19 at 03:04 PM ----------



In my aquarium shooting I typically shoot TVA ISO AUTO (up to 8000) and shutter speeds between 1/125 and 1/250. Aperture varies from wide open to 2 stops down.

Another consideration might be the Sigma 10-20mm f/3.5 EX DC HSM, which B&H is also running at a great special price. I got one of those also and think very highly of it. You could run it with the K-1 in crop mode with IQ at least as good as the K-5 IIs, which is very good indeed, and it would be like a compact, lightweight version of the Pentax DFA 15-30mm in FF mode. The price is very reasonable, and linear distortion at 15mm is virtually absent. Build and design are very, very good.

[aslyfox]

I like the sigma, it isn't a full sensor lens:

This is a super-wide angle lens with a relatively bright F3.5 maximum aperture throughout its zoom range. The lens is in particular suitable for indoor shooting and landscapes. The image format is APS-C and it has a wide angle diagonal viewing range of 102.4-63.8°. The lens has a built-in HSM autofocus motor and offers no provision for screw-drive autofocus.

The lens incorporates an inner focusing system and is constructed with two ELD (Extraordinary Low Dispersion) glass elements and an SLD (Special Low Dispersion) glass element. Further more it has four aspherical lens elements to help correct for distortions.

The minimum focusing distance is 9.4" (24cm) throughout the entire zoom range, which yields a maximum magnification ratio of 1:6.6.

Judging from the field of view specified by Sigma this lens is closer to being a 12-23mm lens than being a true 10-20mm lens.

but I don't know how it would work with the K 1, even in crop mode



Read more at: Sigma 10-20mm F3.5 EX DC HSM Lens Reviews - Sigma Lenses - Pentax Lens Review Database

[aslyfox]

All,

I currently have the FA-J 18-35 f/4-5.6, and while it's an okay lens, it can be a bit soft. I'm wondering if I gain anything by going with the Pentax FA 20-35mm F4, or if I'm just losing 2mm on the wide end for the constant f/4 aperture.

EDIT: The camera is a K-1

Has anyone compared the 2 lenses? I do have the 15-30 and while that's a sharp lens,it's a bit un-wieldy to use in an aquarium, and finding a rubber lens hood for it is a no-go. Even my Ultimate Lens Hood won't fit over it.

since you live in the US, you might investigate the opportunity to spend a little $ and rent lenses that might work and conduct your own trials before buying a lens:

Information on Businesses that offer cameras and lenses for rent - Page 2 - PentaxForums.com

[Craigbob]

since you live in the US, you might investigate the opportunity to spend a little $ and rent lenses that might work and conduct your own trials before buying a lens:

Information on Businesses that offer cameras and lenses for rent - Page 2 - PentaxForums.com

Thanks, I'm already aware of renting lenses and cameras. I was hoping someone here had used them both and could offer an assessment.

[aslyfox]

Thanks, I'm already aware of renting lenses and cameras. I was hoping someone here had used them both and could offer an assessment.

it might be helpful to others if you would add your experiences with renting equipment to that thread