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02-23-2010, 08:59 PM   #1
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Which Lens Would you choose for dark?

Id like to experiment with some night shooting and want to have a lens that is fully capable and can offer the best results for that. Ive seen what this 20817 Pentax SMCP-FA 50mm f/1.4 Standard Auto Focus Lens
lens can do during the day as well as night too and WOW. Ive also read reviews on this lens
Sigma | W/A 28mm f/1.8 EX Aspherical DG DF Macro AF Lens

They are about the same price but the Sigma is a wider angle and macro too, but im sure the Pentax is of better quality.

Im not sure which is the better choice, and was just wondering if i could get some suggestions or have some things pointed out that i might not be aware of. Will be using these on a k7.

thank you

02-23-2010, 09:13 PM   #2
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Depending on what you're taking pictures of, having a fast lens may not be the most important — it may be more about having a good tripod.
02-23-2010, 09:54 PM   #3
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Very good point. I guess i dont have anything real specific in mind, but i imagine id like to try to shoot city scapes, buildings. Im a railfan also so train yards too. Ive read someone comment on using a prime 1.4f during the day and they didnt know why you would use it during the day, but from these pictures Zenfolio | Alfisti | Pentax FA 50mm f/1.4 i cant see why you wouldnt want to use it..is there something im missing?
02-23-2010, 10:40 PM   #4
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The FA 50mm/f1.4 is the most used lens in my kit for either day or night. I find it nice and sharp in either situation. I can't comment on the sigma you mentioned, but you wont go wrong with the Pentax. Plenty of examples on my flickr page of how the 50mm handles the night.

Its great indoors as well, mind you some people feel FOV is a bit too far in doors, but it hasn't been a problem for myself.

02-23-2010, 10:51 PM   #5
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Sounds like the 28mm is the better option; it would be mine from a focal length perspective.

Without knowing the exact comment, it's difficult to say what people mean. What the comment might be saying is that you will not use the 1.4 aperture during the day. The reason is that it let's too much light in that can not be compensated for with lower ISO and shorter shutter speeds.

On a bright sunny day, a K100D with ISO200 and FA31 @ 1.8 can require a shutter speed faster than 1/4000s in certain circumstances. I can not lower the ISO (200 is the lowest) and can not use a faster shutter speed (1/4000s is the shortest) so I'm forced to use a narrower aperture (e.g. 2.8) to prevent over exposure. So I just as well could have carried a lens with max aperture of 2.8 around from that perspective (e.g. 28mm/2.8).
02-24-2010, 08:39 AM   #6
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Thanks guys i appreciate the responses.

Tootall, those are some excellent photos on your flickr. some of the best ive seen.
Sterretje, this is a dumb question im sure but the FA31 is referring to?

Also Im wondering if there is a link somewhere to a graph maybe or chart explaining/showing the usable ranges of the different setting(iso, apeture, shutter) on a dslr for different shooting situations like night with no movement, or bright sunlight with no movement or fast action. or probably evening outdoors with movement would be a tougher one to capture. I know the P mode would set you up, but can you learn these techniques from using the P mode or other modes other than M. Just as a base to get you in the general area.
02-24-2010, 08:59 AM   #7
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I think you are a little confused. Don't forget the depth of field issues using a fast lens, you are btter off using a tripod and the focal length that works for you. 50mm is longish on digital SLR's .... awkward long to be honest.

Use the kits or a 28mm manual lens on a tripod
02-24-2010, 09:50 AM   #8
jas
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QuoteOriginally posted by Alfisti Quote
I think you are a little confused. Don't forget the depth of field issues using a fast lens, you are btter off using a tripod and the focal length that works for you. 50mm is longish on digital SLR's .... awkward long to be honest.

Use the kits or a 28mm manual lens on a tripod
Lol, no doubt Im confused. Might add that to my Signature.

Can you explain "Don't forget the depth of field issues using a fast lens".

I understand what dof is but how is it affected by a fast lens? and what is a fast lens exactly, AF? Thank you for chiming in on the 50mm being longish. I was thinking the 28mm would be a nice wide lens plus with macro too. It could serve as a macro and a night shooting lens....right? A manual would be cheaper. Can you recommend one? am i still sounding confused?

02-24-2010, 10:17 AM   #9
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QuoteOriginally posted by jas Quote
Lol, no doubt Im confused. Might add that to my Signature.

Can you explain "Don't forget the depth of field issues using a fast lens".

I understand what dof is but how is it affected by a fast lens? and what is a fast lens exactly, AF? Thank you for chiming in on the 50mm being longish. I was thinking the 28mm would be a nice wide lens plus with macro too. It could serve as a macro and a night shooting lens....right? A manual would be cheaper. Can you recommend one? am i still sounding confused?

Ok, a fast lens has a wide aperture 9say f/1.4 to f/2.8 being regarded as fast), it's called fast because the wider the aperture the faster the shutter speed for said exposure assuming you keep your ISO in the same place.

Thing is, aperture changes the depth of field. Use f/1.8 and bugger all will be in focus, use f/8 and bang ... most of the image is in focus. Go here ..... Online Depth of Field Calculator

So you can't just stand there and fire off an f/1.4 landscape .... there will not be enough depth. You used my gallery as an example, look at the bridge, see how so much of it is OOF? That was intentional but you see what I mean.

What lens do you hacve right now? 28mm is really not wide on APS, it's the same as 44mm on film ..... 50mm is like 75mm on film. My image of Sam the Record man was taken from a long way back ... a long way.
02-24-2010, 10:55 AM   #10
jas
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Ok, that makes sense. Fast is the speed at which the shutter needs to be for the wide Aperture.

Ok i didnt realize that. So there are draw backs to using a fast lens at night. its not the end all solution to taking great Night shots? So basically the wide aperture lens being used at night for a city scape is turned up to a higher F number because you wont get it all in focus? So you must play with the shutter speed then. hmm.

Did i get that right?

yes i remember the bridge shot And i understand that now. Which category is the Sam the record man in? Only lens i have which i haven't played with yet is a DA* 16-50mm. Still waiting on my camera.

So when someone is taking night time City Scapes they may have a fast lens but they have turned the F up to maybe 7 or 9( just guessing a higher number, dont know what the correct value would be) and have slowed the shutter and used a tripod? I figured the tripod would be used anyway at night and a slower Shutter, but didnt take into account the wide Aperture would limit the DOF.

Thats DOF calculator is handy, but its a bit confusing. thank you
02-24-2010, 11:01 AM   #11
jas
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Found the Sam the Record Man. that looks close, id never guess it was taken far away.
02-24-2010, 11:32 AM   #12
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Yep, you have it figured out.

Sam the record man is a relaly good example, click on "Photo Info" and you'll see I used f/4 even though I needed ISO400, I just needed the extra depth, f/1.4 would be too narrow.

Here is another example .... Zenfolio | Alfisti | Pentax FA 77mm f/1.8

I used f/8 even though the lens is way, way faster than that (f/1.8), now there was enough light thanks to the sun but i still needed ISO400.

Remember the wider the lens the more depth you get, hence your 16-50 is frankly ideal for what you need. Go to my 12-24 gallery, this is an f/4 lens and you'll see i often use f/4 because f/4 at 14mm has way more depth than f/4 at 50mm or75mm.

In the 77mm gallery, you can see here Zenfolio | Alfisti | Pentax FA 77mm f/1.8 that I was struggling. I used f/2.2 on a 1.8 lens but my shutter speed was 1/30 ....... that's too slow ... but i really needed the extra depth of field ... frankly i needed f/8 but was already at 1/30th second and ISO800.

QuoteOriginally posted by jas Quote
Ok, that makes sense. Fast is the speed at which the shutter needs to be for the wide Aperture.

Ok i didnt realize that. So there are draw backs to using a fast lens at night. its not the end all solution to taking great Night shots? So basically the wide aperture lens being used at night for a city scape is turned up to a higher F number because you wont get it all in focus? So you must play with the shutter speed then. hmm.

Did i get that right?

yes i remember the bridge shot And i understand that now. Which category is the Sam the record man in? Only lens i have which i haven't played with yet is a DA* 16-50mm. Still waiting on my camera.

So when someone is taking night time City Scapes they may have a fast lens but they have turned the F up to maybe 7 or 9( just guessing a higher number, dont know what the correct value would be) and have slowed the shutter and used a tripod? I figured the tripod would be used anyway at night and a slower Shutter, but didnt take into account the wide Aperture would limit the DOF.

Thats DOF calculator is handy, but its a bit confusing. thank you
02-24-2010, 11:51 AM   #13
jas
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Wow, what a great Help your replies were. AND having your images with the photo details really helps explain how you obtain them in similar situations too. I didnt realize you could see the details before when i was browsing. Thanks a ton for the help and im going to go study the links you just posted as i looked quickly but wanted to thank you first. But ill definitely be coming back to this thread to re read as i start experimenting, and hopefully this thread helps other in the future as i dont think i found another thread that was as helpful on the subject.

So basically the lens i have is all i need for night shooting? I bought it based on the reviews that told what a great High quality image it produces for a general walk around lens. Not sure on the durability though. Lots of people said they had problems with its AF.

one more question....so what is a really fast lens good for then I mean to utilize the widest F, whats it designed for? Portrait- low light situations/ indoor low light?
02-24-2010, 11:58 AM   #14
jas
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Zenfolio | Alfisti | Pentax FA 77mm f/1.8

Has to be one of my favs. Incredible shot. Probably a great example of what a fast lens is made for.
02-24-2010, 12:29 PM   #15
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QuoteOriginally posted by jas Quote
one more question....so what is a really fast lens good for then I mean to utilize the widest F, whats it designed for? Portrait- low light situations/ indoor low light?
Basically control over depth of field so portraits being number one or times when both shallow DOF and a fast shutter speed is needed.

You can do buildings at night (well let's say late dusk) at say f/4, you just need something to lean on if you don't want to use a tripod. browse the 12-24 gallery, pleanty in there.

If you have the 16-50, wander about a while with the lens at 50mm, that's gonna be exactly what the FA50 loooks like .... as you see, it's narrow.
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