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07-03-2010, 08:20 PM   #1
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Photo quality difference between DA Star 55mm F1.4 vs FA 31mm F1. 8 Limited

Dear Fellow Pentax users,

I am still beginner with D-SLR. I'd like to get some suggestions about these 2 lens.
I understand that DA lens is for the "half frame" DSLR and the FA Len is designed to use with Full Frame or regular film SLR. However, it can still use on the K10D, K20D and the K7.

When the FA 31mm lens is used on a k10D, it won't be 31mm. It would be like a 48mm lens because of the cropping.

I'd like to know a few things. When using lens on a K10D
1.) even after the crop, which one has wider angle?

2.) which one has sharper image outdoor?

3.) which one has sharper image indoor? I believe the DA 55mm should have better image in this category. However, I wonder if the FA lens will cover more view due to wider angle..

4.) If I buy both lens new now, are they still make in Japan ? or there are chance that they will be made in Vietnam? I know the new FA 50mm no longer manufacture in Japan.

5.) for long run, which one is better investment?

6.) this is not related to lens. I will be visiting Japan. I wonder if the k-7- limited really worth getting if I jump from K10D ??

a lot of thanks in advance..

Tin

07-03-2010, 08:27 PM   #2
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*55/1.4 is a lens trying to replicate *85/1.4 on APS-C, but the depth of focus is different from *85

FA 31 is wide-angle on 35mm film camera with a classic view-angle, however on your APS-C, it is like 43mm lens.

Anyway, both of the two lens are known as good lens with sharpness and beautiful bokeh. I think they are good for potrait shooting, giving you a dream bokeh.
07-03-2010, 08:44 PM   #3
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Hi henryjing,

Thanks for your quick reply and information.
So, you are saying the FA 31mm/1.8 should have shorter focus depth comparing with the DA* 55mm/1.4 when using on my K10D .

I would say 60% of my use would be indoor and 40% would be outdoor. And 90% of the photos are for babies between 1 month to 2 years old.

So, I kind of need a faster lens. At the same time, because they can't stand still, I think wider angle would help.

Which one would you suggest? I already have a FA 50mm/1.4. thinking to trade-in for one of those ..

Thanks
07-03-2010, 09:39 PM   #4
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QuoteOriginally posted by tin008 Quote

When the FA 31mm lens is used on a k10D, it won't be 31mm. It would be like a 48mm lens because of the cropping.

I'd like to know a few things. When using lens on a K10D
1.) even after the crop, which one has wider angle?



a lot of thanks in advance..

Tin
31mm is always wider than 55mm. The true focal length of all lenses is what is written on them. The size of the sensor changes the angle of view.

07-04-2010, 04:16 AM   #5
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The FA 31mm is LEGENDARY. Of the two I'd say that's your pick, especially if you already have an FA 50mm.

The 31 is sharper, renders bokeh beautifully and is much better built.
07-04-2010, 06:26 AM   #6
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QuoteOriginally posted by noahpurdy Quote
The FA 31mm is LEGENDARY. Of the two I'd say that's your pick, especially if you already have an FA 50mm.

The 31 is sharper, renders bokeh beautifully and is much better built.
I disagree. Though the 31 admittedly has a much nicer feel to it, being all metal and kind of "old school", the build quality of the DA*55 is actually quite excellent. The 31 is known as a "magical" lens that transcends the usual description of a good lens. Whether you believe in its magic or not you won't know until you've tried it. Most people around here do, but there are a few of us that haven't drunk the kool-aid. Don't get me wrong, it's an excellent lens, but no way is it appreciably sharper than the DA*55. And the bokeh, though it may have a slightly different look to it, is no less desirable on either lens. It really just comes down to what focal length you want and how much you want to spend. You're not going to make a mistake with either one of these. I should add, though, that if portrait ability is in any way a consideration, then I would lean heavily toward the 55. It's a fantastic portrait lens. I use it nearly every day for that purpose and consider it a vital tool for my business.
07-04-2010, 06:54 AM   #7
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I have both of the lenses (DA* 55 and FA31 Limited) and both are superb lenses if you know what to look for. The 31 is not very suitable for portraiture because of the exaggerated perspective (noses will appear larger). It all depends on what you want to do with it.

I think that the FA31 is a better lens for running children (it focuses faster than the DA*55).
07-04-2010, 09:01 AM   #8
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Basically, FA 31mm is better for baby shooting.

*55 may be a bit longer for taking pic of baby and *55 focus more slowly.

not sure, but i heard that SDM may have some problem on K10D.

QuoteOriginally posted by henryjing Quote
*55/1.4 is a lens trying to replicate *85/1.4 on APS-C, but the depth of focus is different from *85

FA 31 is wide-angle on 35mm film camera with a classic view-angle, however on your APS-C, it is like 43mm lens.

Anyway, both of the two lens are known as good lens with sharpness and beautiful bokeh. I think they are good for potrait shooting, giving you a dream bokeh.


07-04-2010, 10:33 AM   #9
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SDM works perfectly fine on a K10 as long as you have up-to-date firmware.
07-04-2010, 10:48 AM   #10
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I have the 31mm plus the other two Limited lenses, but not the DA 55mm. Of the three limited, the 31mm gets used more than the 43mm and the 77mm. I also had the FA 50mm 1.4 which sold because it almost never get used. I find the 31mm focal length more suitable for my shooting style plus the 31mm is more suitable for indoors. When you say Portrait, do you mean head and shoulder shots? If that is the case, I would say 55mm to 77mm is more suitable. However, I much prefer the 43mm in that regard, again, only in my situation.
07-04-2010, 11:29 AM   #11
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QuoteOriginally posted by DogLover Quote
I disagree. Though the 31 admittedly has a much nicer feel to it, being all metal and kind of "old school", the build quality of the DA*55 is actually quite excellent. The 31 is known as a "magical" lens that transcends the usual description of a good lens. Whether you believe in its magic or not you won't know until you've tried it. Most people around here do, but there are a few of us that haven't drunk the kool-aid. Don't get me wrong, it's an excellent lens, but no way is it appreciably sharper than the DA*55. And the bokeh, though it may have a slightly different look to it, is no less desirable on either lens. It really just comes down to what focal length you want and how much you want to spend. You're not going to make a mistake with either one of these. I should add, though, that if portrait ability is in any way a consideration, then I would lean heavily toward the 55. It's a fantastic portrait lens. I use it nearly every day for that purpose and consider it a vital tool for my business.
The 31 is indeed sharper at wider apertures (Noticeably so up to f/2.8 in my use). And if the OP is taking pictures of babies, he will likely be using a shallow depth of field and thus desire sharper wide apertures. I own both lenses and while the build quality of the 55 is great, I like the all metal construction and adjustable aperture diaphragm.

If he'd like to branch out into portraiture, or if money was a concern my recommendation would be the 55 hands down however.
07-04-2010, 12:52 PM   #12
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QuoteOriginally posted by tin008 Quote
When the FA 31mm lens is used on a k10D, it won't be 31mm. It would be like a 48mm lens because of the cropping.
Compared to ow that same lens would look on a film camera, yes. Do you own a film camera? If not, forget you ever heard the term "crop factor". The FA31 is still 31mm, which means it is barely half as long as the DA*55. If you've got the kit lens (18-55), the FA31 will have exactly the same focal length and field of view as your kit lens set to 31mm, and the DA*55 will be exactly the same in these respects as the 18-55 as set to 55mm. Only if you need to compare a digital camera to a film camera do crop factors come into play; it has no relevance when comparing different lenses but both on a digital camera.

QuoteQuote:
2.) which one has sharper image outdoor?
Both are incredibly good. Unless you are setting up tripods and shooting resolution charts, there's basically no reason to assume you'd be able to see the incredibly tiny differences that might exist in quality. Actually, even if you *are* setting up tripods and shooting resolution chart, chances are excellent you'd never be able to tell the difference in quality.

The difference in field of view is huge, though. The 31 is a "normal" lens, the 55 a telephoto.

QuoteQuote:
which one has sharper image indoor?
See above.
07-04-2010, 02:36 PM   #13
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QuoteOriginally posted by tin008 Quote
1.) even after the crop, which one has wider angle?
Cameras do not change the focal length of a lens attached on them. A 31mm lens is still 31mm; a 55mm lens is still 55mm.

However, they do change the angle of view. So the FA31 (which is actually 32mm) will have the equivalent angle of view of 48mm on a full-frame film camera. And the DA*55 will have the equivalent angle of view of a 84mm lens. This in no way matters unless you are sharing lenses across different systems. As Marc said, forget the crop factor nonsense if you are only using APS-C.

QuoteOriginally posted by tin008 Quote
2.) which one has sharper image outdoor?

3.) which one has sharper image indoor?
Where you shoot has nothing to do with sharpness. However, the aperture you are using does. Both lenses are sharp. The FA31 is sharper until about f/4 but not so much that you'd likely notice. Your technique and skill as a photographer will have a lot more to do with how good your images look.

QuoteOriginally posted by tin008 Quote
If I buy both lens new now, are they still make in Japan ? or there are chance that they will be made in Vietnam?
It doesn't matter, but yes, they will likely be made in Vietnam.

QuoteOriginally posted by tin008 Quote
I wonder if the k-7- limited really worth getting if I jump from K10D ??
The K-7 will not take better pictures. But if you strongly need some of the newer features (eg video) it may be worth it to you.
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