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Forum: Pentax SLR Lens Discussion 01-20-2013, 09:16 AM  
Differences between Tamron and Sigma 18-200mms?
Posted By Marc Sabatella
Replies: 10
Views: 1,835
The 18-xxx and 28-xxx lenses are only f/3.5 at the short end. By 55mm, they'll be f/4-ish just like the 55-300. So you can completely forget any difference in speed - in fact, the 55-300 will actually be faster by the time you get to the longer.

You can also forget any miniscule differences in quality between the different 18-xxx or 28-xxx lenses - none of them are good enough to make anyone take notice, or so bad you can't take snapshots with them. The 55-300 *will* be noticeably better than any of the others.

Really, though, the main consideration is simply the focal length range. The 18-xxx lenses will allow you to use only one lens and not feel too limited. If sometimes you want more reach, you can always just crop. The 28-xxx lenses might trick you into thnking you can get away with only one lens, but you'll really miss the 18-28mm at the wide end. This will be *way* more significant than any quality difference between any of these lenses.

The 55-300 is indeed better enough to possibly matter, but of course, there is no way that can be your only lens.

So your choice is really between the 18-55 / 55-300 combo versus an 18-xxx, where you trade some noticeable improvement in quality against convenience.

Nut nne of these options will be worth a darn in low light - they'll all be f/5.6 or so by the time you get to the telephoto range. Much better to get a used manual prime lens like a 100 or 135 if you are trying to do concert photography on the cheap.
Forum: Pentax SLR Lens Discussion 01-20-2013, 09:01 AM  
Teleconverter for normal fast prime?
Posted By Marc Sabatella
Replies: 7
Views: 1,574
You'll almost certainly do far better simply cropping an image from the 50 than using a TC with it, and it's less to carry and fiddle with. But I can also vouch for M100/2.8 as a great option if you want that focal length. Although you might actually find the M135/3.5 - only marginally larger/heavier - a better choice. Easier to find, cheaper, and it's probably more often you'd find 100 too short than 135 too long. And for the cases where 135 *is* too long, you can always go back to the shoot-50-and-crop plan.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:55 PM  
M Lenses - Purple Fringe Masters
Posted By Marc Sabatella
Replies: 39
Views: 4,520
Purple fringing (PF) can be caused by lens chromatic aberrations (CA) as well as by other things. And lens CA does not always manifest as PF. But because lens CA is one cause of PF, there definitely are differences between lenses with regard to PF.

I have or have had most of the common/ cheap M lenses and a couple less common ones: 28/2.8 (I), 50/1.7, 50/2, 100/2.8, 120/2.8, 135/3.5, and 200/4. I've never done a controlled PF or CA test except between the 100, 120, and 135. Among these three, the 100 and 135 are both pretty bad, the 120 noticeably better. I don't tend to shoot 50mm in the sort of situations where PF would manifest, so it's hard to say with those. The 28 seems about average with respect to PF.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:42 PM  
Owners manual for DA 18-55 WR?
Posted By Marc Sabatella
Replies: 5
Views: 3,223
Well, not too far from zoom lenses that label themselves as macro in order to pump up sales figures, but not close to a true macro lens.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:40 PM  
Fast lens for low-light photography
Posted By Marc Sabatella
Replies: 24
Views: 3,438
Says who? Sharpness is a relative term, and DOF is shallow enough at f/1.7 that very little is in focus. But the part that is is as sharp as any other lens used wide open, more or less. And in case case, shooting in low light, I *guarantee* that differences in sharpness between lenses is of almost no significance. The biggest limiters to sharpness will camera shake, subject motion, high ISO noise, and focus issues (whether using MF or AF, getting focus *exactly* where you want it is difficult with fast lenses). You might as well forget anything you heaqr about such and such a lens being 7% softer wide open than some other lens - it just has no real world relevance.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:35 PM  
Comparing my M28/2.8 v1 and Vivitar 28/2.8 k06
Posted By Marc Sabatella
Replies: 8
Views: 1,534
I see no reason to assign any differences in color have anything to do with lens - it's much more likely a simple matter of the camera picking a slightly different WB.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:30 PM  
50MM 1:2 M VS A (film era lenses)
Posted By Marc Sabatella
Replies: 14
Views: 2,451
It might seem that way at first glance, but this is not true. With M lenses, the aperture ring has no effect whatsoever when not in M mode. You can set it to f/2, f/5.6, or f/22, and you'll get the exact same shutter speed and the exact same image - and f/2 image. That is, it is impossible to get a picture at any aperture other the f/2 - no matter where you set the aperture ring, f/2 is what you get. Only in M mode does the aperture ring actually function to control aperture. Whereas with A lenses, while the aperture ring continues to be completely ignored in all modes other than M, you can control aperture using the camera just as you would with a modern lens.
Forum: Pentax SLR Lens Discussion 01-12-2013, 04:21 PM  
Super wide for people photography
Posted By Marc Sabatella
Replies: 14
Views: 1,616
The distortion you see is about 1% due to lens defects and 99% due to simple perspective. That is, the most distortion-free lens in the entire world as measured objectively would still show what you perceive extremely distorted people in the corners, because that's what happens when you take a frame that is considerably wider than the printed/display image itself and distort it to fit. If you want a large group of people to not look distorted, you need to shoot with a longer lens from farther away (or distort the image in PP to counteract the natural and correct perspective the lens is showing you).
Forum: Pentax DSLR Discussion 11-08-2012, 09:05 PM  
Posted By Marc Sabatella
Replies: 16
Views: 1,967
Jim gave a technical explanation, and Google would surely supply with your hundreds upon hundreds more pages of information. But let me try to give a non-technical explanation that will hopefully be more immediately helpful.

A given lens can behave very differently from one camera to another, depending on the sensor size. A 40mm lens, for example, produces a slightly wide angle image on a traditional film camera, but a narrower view - like a telephoto lens - on an a traditional DSLR like yours. A 50mm lens produces a "normal" image - neither wide nor telephoto - on a film camera, but a definitely telephoto image on your camera.

"Crop factor" is a term used to describe how much the images changes between cameras. Specifically, the crop factor of 1.5 means a 50mm lens on your camera produces an image similar to what you'd get from a 75mm lens on a film camera.

So the question of what focal length lens you want depends on what camera you want to use it on. And as I said, 50mm is a decent portrait focal length on your camera, but not so good as a general purpose indoor lens because it is too long. Conversely, 50mm is a good general purpose indoor lens on film, but not so good as a portrait lens because it is too short.
Forum: Troubleshooting and Beginner Help 11-08-2012, 08:41 PM  
Dumb question about resolution on Optio RS1500
Posted By Marc Sabatella
Replies: 6
Views: 1,106
Or, a 14x11" print at 300 dpi. The same exact image can be printed at any size you print. The bigger you print, the fewer dots per inch that works out to be. You don't do have to do a thing, and neither does the paper. Anyone in the print business already knows they can print your image any size they want, and the resolution will be the number of pixels divided by the number of inches.

Here's another way of looking at it. Say you have a 48-oz box of breakfast cereal, and it says it contains 12 4-oz servings. Would you have to do anything to change that into a box containing 16 3-oz servings? 8 6-oz servings? No, that takes care of itself. Similarly, you don't have to do anything to change your image from 60x45 at 72dpi to 14x11" at 300dpi. It takes care of itself.
Forum: Troubleshooting and Beginner Help 11-08-2012, 08:26 PM  
Lens filter a good idea?
Posted By Marc Sabatella
Replies: 22
Views: 2,551
Do a search and you'll find at least 100 previous threads on the subject, plus web articles. Some people are convinced the small degree of protection they offer is worth the image degradation. Others just try to be careful.
Forum: Troubleshooting and Beginner Help 11-08-2012, 08:24 PM  
SMC Pentax-A 50mm F1.7 Problem
Posted By Marc Sabatella
Replies: 18
Views: 3,352
Not sure if you've already figured this out or not, but the above is *not* true. I mean, yes, it's true that you don't get an indication of aperture, but that doesn't meant you can't get an indication of over/underexposure. You just need to get the camera to stop down the lens for you, by doing DOF preview. Or simply hit the Green button so the camera will automatically stop the lens down, take a meter reading, and set an appropriate shutter speed for you. Do a search and you should be able to find any number of articles explaining more about how to use manual lenses. Some of us use them a lot! With the Green button and DOF preview, it's really not much less convenient than using an "A" lens.
Forum: Pentax DSLR Discussion 11-06-2012, 11:17 AM  
K200D battery drains very fast :(
Posted By Marc Sabatella
Replies: 18
Views: 6,001
Three year old rechargeable batteries will indeed not do as well as fresh ones. Probably just time to buy a new set.
Forum: Pentax DSLR Discussion 11-06-2012, 11:16 AM  
Posted By Marc Sabatella
Replies: 16
Views: 1,967
To echo what others have said - 50mm is fne, if one the short side, for portraits on APS-C (the format/size of your camera), since it corresponds to 75mm on the most popular format for film cameras (variously called 135, 35mm, or FF). And you can get used 50mm lenses very cheap if you're OK with manual focus. But 50mm is much too long for "most" indoor photography. Was fine for 135 format, but too long for APS-C due to the "crop factor".

Meaning, if I were you, Id be looking at the DA35 (similar price as the 50) for most indoor usage, and maybe an old manual 50 for portraits.
Forum: Pentax DSLR Discussion 11-06-2012, 11:11 AM  
New K7 bad results
Posted By Marc Sabatella
Replies: 30
Views: 3,399
Looks to me like you might have aimed focus at the right eye, but in the second picture, the hands were close enough to the selected focus point that the focus was there instead. As for color difference, all I see is a minor difference in how they happened to interpret WB in that particular shot. Shoot 100 images and you'll see similar minor variations in all of them, but chances are you'd find you preferred the K10D half the time, K-7 the other half in a blind test.
Forum: Troubleshooting and Beginner Help 11-06-2012, 11:06 AM  
White Balancing questions
Posted By Marc Sabatella
Replies: 10
Views: 1,422
"Exactly as they looked" is subjective. Everyone's eyes perform their own internal WB, and everyone does it a little differently. If the light is orange (eg, typical incandescent bulbs), then the color really *is* orange. It's just that your eyes fool you into thinking you seeing white and other colors. Setting WB tries to get your camera to perform the same lie your eyes perform, but again, its subjective. So no, there is no way a camera can reproduce the exact same lie your eyes are telling you. It will try to come close, though. So to a rough approximation, sure, setting WB in camera will get you kind of close to what you imagied yourself to have seen - to the lie your eyes told you. But you may still want to fine tune it in PP.
Forum: Troubleshooting and Beginner Help 11-06-2012, 11:02 AM  
White Balancing questions
Posted By Marc Sabatella
Replies: 10
Views: 1,422
If you shoot RAW, setting WB in camera is not necessary. It will affect the starting point for your PP, but you'll be able to get the exact same results regardless of where WB was set in camera. Not true for JPEG - the further off your WB is, the harder it will be to correct.
Forum: Troubleshooting and Beginner Help 11-06-2012, 10:59 AM  
Focusing issues with a K-m (K2000)
Posted By Marc Sabatella
Replies: 10
Views: 1,986
No it doesn't. You need to explicitly turn it off. It is automatically turned off if you use the 2-second timer, though.
Forum: Pentax SLR Lens Discussion 11-03-2012, 08:48 PM  
Focus problem with 18-55WR on K5
Posted By Marc Sabatella
Replies: 12
Views: 1,287
As always, sample pictures will be necessary to say whether the problem is the lens, the camera, your technique, or your expectations.
Forum: Photographic Industry and Professionals 10-27-2012, 07:21 PM  
Pentax Outlet In Denver!
Posted By Marc Sabatella
Replies: 22
Views: 7,850
No, I'm in Wheat Ridge, and the Wolf->Mike's location I am referring to is at 38th & Wadsworth. Interesting to see that it's not just my location, though!
Forum: Pentax SLR Lens Discussion 10-27-2012, 07:13 PM  
Suitable wide angle for K5?
Posted By Marc Sabatella
Replies: 26
Views: 3,334
I think you're confused. Sure, some lenses have a small amout of barrel distortion, but that's not what you're seeing. Yu're seeing the *inevitable* effect of taking a wide scene and compressing it into a print or computer screen that is nowhere near as wide as the scene. This is called "perspective distorton" and it is not a lens defect. In fact, any lens that failed to produce this effect would be highly defective.

What do you mean, "regular 18-24 wide angle"? I'm not aware of 18-24mm lens and would be surprised if one existed. Maybe you mean, what's the difference between the 18-24 portin of the range of two different lenses - the 18-55 and 12-24, say? Answer: nothing. All lenses when set to 18mm (assuming they include that focal length) produce exactly the width of image. The 12-24 is only wider that the 18-55 if you use the former in the 12-18 range.
Forum: Troubleshooting and Beginner Help 10-27-2012, 06:58 PM  
Indoor Shooting
Posted By Marc Sabatella
Replies: 8
Views: 2,287
What I always say:

Stop thnking in terms of "settings". Most settngs *no not matter*, except for the three that *always* matter: shutter speed, aperture, and ISO. These are the basics of exposure. The trick in low light is to get a fast enough shutter speed, and that is done by using a lagre and apertur ena as high an ISO as you need. None of these are simple "settings" you'd make in a menu then leave alone (well, ISO, maybe) - they are thingns you control shot by shot. Or set up to allow the camera to control shot by shot. Again, your starting point is to learn everything about these three parameters,a nd forget that any other camera settngs even exist.
Forum: Troubleshooting and Beginner Help 10-27-2012, 06:47 PM  
K-M focus confirmation bypass
Posted By Marc Sabatella
Replies: 9
Views: 1,099
Look for a way to program one of the rear buttons to temporarily cancel AF. On my K200D, it's the OK button that can be programmed to do that, via one of the custom functions.
Forum: Troubleshooting and Beginner Help 10-27-2012, 06:41 PM  
Pentax K200 - pictures in low light
Posted By Marc Sabatella
Replies: 15
Views: 4,423
No camera can do everything perfectly, but as e images show very clearly, the problem is not a camera limitatin but the simple fact that you can't stop motion on low light with slow shutter speeds. No camera can. There is no getting around the need for more light and/or hgher ISO to get the shutter speed. The K200D, like any camera, will do better with more light. Sports photography in low light, especially with slow lenses is difficult, and that remain true regardless of what camera you use.

For the OP: you specifically ,entioned getting better results from your P&S, bt I think you will find on cloer examination that any shot that looked better pon your P&S was taken in better light and thus was able to get faster shutter speeds. Or, you used flash. Again, there is absolutely no way any P&S camera is going to do better in the same light. More modern DSLR's will do *slightly* better that the K200D in that you'll be able to get a stop or so less noise for the same shutter speed, but you'll still have to make sure you ahve fast enogh shutter speeds, and you're not even slightly close to having fast enough shutter speeds as it is.

Bottom line: you need more light, not a new camera. A faster lens will help somewhat, but again, you're *way* off of having fast enough shutter speeds, and a faster lens won't make up the difference.
Forum: Photographic Industry and Professionals 10-21-2012, 09:09 AM  
Pentax Outlet In Denver!
Posted By Marc Sabatella
Replies: 22
Views: 7,850
I haven't made it by yet, but hope to soon. Meanwhile, though, I've noticted a sign at the neighborhood Wolf (which is now completely closed that says Mike's Camera is coming soon. They stopped carrying Pentax long ago, but still, I'm glad I'll still have a nearby camera store for accessories and so forth. And who knows, maybe someday they'll carry Pentax again.
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