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04-15-2008, 01:42 PM   #31
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Timarete, the problems you face are manyfold and cannot be solved with the lens alone. You need to fix several things in your workflow:

a fast, wide lens is of course very desirable. Options include the Sigma 1.(/20 or 1.8/24 or the older Pentax FA 2.0/24 mm (the difference between 1.8 and 2.0 is less than half an f-stop)

but for many objects you need to close the aperture down anyway to have a decent and necessary depths of field. Otherwise you get the same effect your friend complained about: the nose is sharp, but the eyes are not.

the latter statement would imply, that under many circumstances a not-so-fast lens would do, like a more wide-spread 2.8 variety

I personally would consider a 28-300 zoom lens as a no go for museums, because the image quality is poor wide open and needs considerable stepping down (at least two steps) to really improve

the cheapest fast and really good lens I can think off is the Pentax FA 2.0/35 mm , which is not really wide on a DSLR, but a capable tool. It is even good enough to add a close-up lens (preferably of the achromatic variety, available cheaply from Canon or Minolta via ebay) for really small details

Otherwise for really wide settings the Sigma 17-70 might be an option, because it sports 2.8 at the widest angle, as does the considerably more expensive Pentax 16-50.

if you work in poor artificial lighting, you should not only get your white balance adjusted, you should also try to set the exposure correction to +1 f-stop (which prolongs the exposure time accordingly) and I expect you to whitness a marked improvement in image quality. (That is, because camera meters usually underexpose in artificial light, which leads to heavy shadows etc.)

the "string tripod" is an old school trick, which was widely in use (and there were even dedicated strings sold) in the 50s and 60s - and it still works

as often as possible I try to use a wall as a tripod. This works best in portrait orientation of the camera, where you can press the camera bottom forcefully against the wall. This enables you to hold steadily quite long exposure times.

My own low light equipment usually consists of three lenses: 2.0/24 - 1.4 or even 1.2/50 and 1.4/85. For really wide angles I don't have a fast lens, because there is none, which I can think off. But as you can hold longer exposure times with shorter focal lengthes, actually a 2.8 or even 3.5 is not too bad. For me, this is covered by my Sigma 18-50 2.8 (I use sometimes a Sigma 15-30mm 3.5 and otherwise the old Pentax 20mm 2.8 - if I need the best quality).

Ben

04-15-2008, 01:49 PM   #32
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Can I just repeat (since people have made contrary suggestions since) that the physics of the situation demands a fast 20mm lens (or wider). That way with 6 feet of clearance you can shoot a 6 foot tall object in portrait mode. And you will not need to worry about DOF then.

The 35mm lenses are nice but in this application will not do the job.
04-16-2008, 11:36 AM   #33
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Speed versus width

Deni: Yes, I might end up printing some of the photos, but the largest possible size would be about 8x10. Most of the shots will be printed smaller, if at all. My goal is to have shots that would be good enough for printing in an average-sized book.

Ben_Edict: Many thanks for the very helpful reply! You are absolutely right about the speed I had targeted as being too fast to give me enough DOF. I found this online calculator that helped me get some concrete numbers to evaluate:

Online Depth of Field Calculator

rparmar: You are absolutely correct about my need for a lens wider than 35mm, as the "Dimensional Field of View Calculator" on this page confirmed for me:

http://www.tawbaware.com/maxlyons/calc.htm

I worked out a chart for three different focal lengths, attached here. If these numbers are correct, then I'll need to stop down for the portrait busts and smaller objects in order to have them fill more of the frame.
Attached Images
 
04-16-2008, 05:53 PM   #34
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Timarete

To keep you under your $400 budget you could choose some older Pentax lenses. Two very fine lenses with the same focal length are the smc PENTAX-A and F ZOOM 1:4 24~50mm. Both are exceptional for the price. For your needs you will have to use at least f4 anyway.

For smaller and tighter objects the smc PENTAX-F ZOOM 1:3.5-4.5 35-70 mm has great sharpness. It also has a macro feature at 70mm. There is an A version of this lenses as well.

The 24~50's go for around $200 and the 35~70's less than $100. The A versions are manual focus and the F versions have autofocus.

You wouldn't go wrong either with the new 35mm Ltd macro or even the 50 macro to photograph smaller objects. You will not match the macro sharpness of either of these lenses with a zoom.

One nice thing about all of these lenses are their compactness. Even the 24~50.

04-17-2008, 12:01 AM   #35
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Do you have the kit lens? If yes give it a shot in a museum, or place with similar light to that of a museum.

Also try the string trick and see if it helps you. Don't expect to get it working at the first try though.
04-17-2008, 02:04 AM   #36
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QuoteOriginally posted by rparmar Quote
Can I just repeat (since people have made contrary suggestions since) that the physics of the situation demands a fast 20mm lens (or wider).
Of course, it would be nice to have a 18mm or 20mm lens with an F/1.4 aperture. Unfortunately it doesn't exist. As the original poster insisted on shooting in available light in poorly lit museums, it seems that it would be better to opt for a slightly longer focal length, as there are many fast 24mm to 31mm lenses available.

Here are the lenses that I own in this range, with some comments regarding their usefulness for the task (I purposely omitted zooms, as most wide angle zooms are too slow and have too much distortion and aberrations when used wide open):
- Tamron Adaptall SP 17/3.5: not very fast, ugly greenish tinge, corners soft until F/8.
- Super Takumar 20/4.5: good lens but flares easily and definitely too slow.
- Zeiss Jena Flektogon 20/4: a bit soft wide open, it becomes a superb lens at F/8. No distortion. Much too slow.
- Pentax FA 20/2.8: good lens, sharper and more contrasty than the Takumar 20/4.5, but some distortion and aberrations visible at f/2.8. Still usable though.
- Sigma 20/1.8 EX: fast but not sharp until at least F/2.8, even in the center of the frame, effectively negating the wide aperture advantage.
- Super-Takumar 24/3.5: very good lens but not fast enough.
- Tamron Adaptall 24/2.5: not quite usable wide open (borders too soft), making it too slow at working apertures.
- Sigma 24/1.8 EX: sharp and contrasty, even wide open. Useful close up feature. Fast. The best compromise IMHO.
- Super-Takumar 28/3.5: Very sharp but not fast enough.
- Tamron Adaptall 28/2.5: Good from F/4, making it not very fast for a 28mm lens.
- Sigma 30/1.4: good contrast but poor edge performance. Even at F/8, the corners are still visibly soft, making this lens suited only for centered subjects (no bas-reliefs shots covering the whole frame).

Cheers!

Abbazz
04-17-2008, 04:41 AM   #37
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I'm surprised that nobody has yet suggested the King of Lenses for the Pentax - the 31mm f/1.8 Ltd

I have one - and they're not cheap - and it is the sharpest lens I own, just about at all apertures. It should be fast enough to do the handheld low light thing, and 31mm should get you in control of most situations I would have thought.

Having said all that, however, I must admit to not having tried my 31mm in a museum - I'm afraid I don't "do" museums... Each to their own, I guess.

But I have used it in low light situations elsewhere, and it has been surprising just what good results I've had from it. You can also boost the ISO, or use flash, to allow you to stop down a bit as well and increase your depth of field when needed.

I'd certainly agree with the post recommending a camera with built-in shake reduction, like the Pentax. I have a K10D and a K20D, and both give outstanding results, with the new CMOS sensor of the K20D being somewhat better at higher ISOs than the K10D.

Hope that helps just a bit...
04-17-2008, 05:13 AM   #38
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QuoteOriginally posted by Derridale Quote
I'm surprised that nobody has yet suggested the King of Lenses for the Pentax - the 31mm f/1.8 Ltd
Probably because he said he has a budget of $400, I doubt the 31mm f/1.8 ltd goes for that sort of money, and he needs a wide lens. The 31mm is more of a normal lens.

04-17-2008, 06:20 AM   #39
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I've recently got myself a Sigma 17-70 f2.8 and it might work for you. Here's some shots I got at the War Memorial which aren't very good but will show you if it'll work for ya. Some use flash, some don't all are hand held.







And some better shots in this thread https://www.pentaxforums.com/forums/post-your-photos/24520-stained-beauty.html

This lens also falls within your price range Hope it will help you make a choice.

EDIT: You can see the exif data when the images are opened.

EDIT PS: If you can still frame your object a trick I recently learned (regarding flash and glass enclosures) is to get a rubber lens hood and press that against the glass. You wont get any reflection from flash back off the glass at all.

Last edited by KrisK10D; 04-17-2008 at 06:30 AM.
04-17-2008, 06:27 AM   #40
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I quickly skimmed the posts, but did anyone mention that the museum objects are STATIONARY? You don't really need a fast lens. Just use the Shake reduction to get steady shots at 1/5s with whatever lens(es) you have. Additionally you'll have plenty of depth-of-field.
04-17-2008, 06:34 AM   #41
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My standard museum lens has been the 35mm f/2. I am usually shooting pieces that range from an inch or two to six or seven feet in height.

I recently received a 12-24 and will be trying it in my favorite museum shortly. The 35mm works well, though.

One advantage to musuems is nothing moves so I can take as many shots as I want.
04-17-2008, 07:17 AM   #42
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I vote for DA* 16-50 f/2.8

Edit: I just saw the $400 budget... never mind.
.
04-17-2008, 03:50 PM   #43
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QuoteOriginally posted by Abbazz Quote
Here are the lenses that I own in this range, with some comments regarding their usefulness for the task...
A useful list that was fun to read through. Assuming f/2.8 is fast enough -- and it had better be since there are few options otherwise -- I'd say the Pentax FA 20/2.8 ("usable" wide open) and the Sigma 20/1.8 EX (sharp at f/2.8) are the best options from what you say.

QuoteOriginally posted by Abbazz Quote
(I purposely omitted zooms, as most wide angle zooms are too slow and have too much distortion and aberrations when used wide open
This is mostly true. If f/4 was fast enough the Pentax 16-45mm would be an option since it is remarkably accurate wide open and to the edges.
04-17-2008, 05:42 PM   #44
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QuoteOriginally posted by rparmar Quote
A useful list that was fun to read through.
Thanks.

QuoteOriginally posted by rparmar Quote
Assuming f/2.8 is fast enough -- and it had better be since there are few options otherwise -- I'd say the Pentax FA 20/2.8 ("usable" wide open) and the Sigma 20/1.8 EX (sharp at f/2.8) are the best options from what you say.
If you insist on 20mm, the Pentax FA is your best bid (the DA 21mm Limited seems to be a good lens as well, but it is 0.5 stop slower than the FA and limited to crop format cameras). Unfortunately, the FA 20mm is hard to find and its current price on the second hand market exceeds the budget of the original poster. Regarding the Sigma 20/1.8, I said it was "not sharp until at least F/2.8, even in the center of the frame," which means that it is barely sharp in the center at F/2.8, with blurry edges. Believe me, the Sigma 24/1.8 is a much much better lens, fully usable wide open. 24mm is still adequate for museum photography and there are two more advantages against the 20mm: the 24 is cheaper and it exhibits less distortion.

Cheers!

Abbazz
04-17-2008, 06:12 PM   #45
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Thanks for the clarifications! After I got my kit I was originally looking for a 20, 24 or 28mm prime but ended up with the 16-45 since nothing was available reasonably and nothing seemed likely to be better quality than the zoom. I was willing to take the extra stop hit but the OP is likely better with what you recommend.
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