Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Sony Alpha dSLR / Konica Minolta dSLR, Sony SLT

Reply
 
Thread Tools Search this Thread
Old Mar 9, 2006, 8:28 AM   #11
Senior Member
 
Join Date: May 2005
Posts: 338
Default

Focal length is a reference to the distance between the lens and the film on a camera. For your 5d, you will need to multiply the focal length for any lens by 1.5 to get a 35mm equivalent because the APS-C sensor is smaller than a 35mm film frame. It sounds complicated, but it really is not, for example... The 90mm Tamron (that Jim recommended above) when mounted to a 35mm camera has a focal length of 90mm. On a KM 5d, the focal equivalent is 1.5x90, or 135mm. For the 100mm lens (that Jim also recommended above) the focal length equivalent is 150mm on the 5d, as 100mm x 1.5 = 150mm . As far as magnification goes, the higher the focal length, the more magnification. The magnification on a 100mm lens is twice that of a 50mm lens and half that of a 200mm lens.

I hope that helps, I'm not positive that I am answering the question you're asking. Here's a couple links that I hope explain focal length...

http://www.dpreview.com/learn/?/key=focal+length

http://hyperphysics.phy-astr.gsu.edu...pt/foclen.html

The bottom one also has links defining chromatic aberraton (CA) and spherical aberration (SA) of lenses. Very graphic and simple.

I think 400mm is a bit long to start with, given the 1.5 multiplication factor of the camera's sensor- making it a 600mm lens. You could probably get a good 70-210 or 75-300 for the same price. I recently bought a nice Minolta 70-210 f3.5-4.5 for ~$100. It's not quite as good as the constant f4 version by most accounts, but it is compact, light and about half the price. It is quite sharp and actually a bit brighter at the short end (70mm) though a bit dimmer at the long end (210mm). Since all lenses are a compromise, you will need to define for yourself where you will compromise. Typically 3x zooms are considered the high end of acceptable optical performance (sharpness). The 70-210 is an example of such a zoom ( 70 x 3 = 210). Zooms with higher internal magnification than that tend to be very dim, and fuzzy. They are generally cheaper because of that, and new photographers often buy such zooms. The factors you will compromise on are- optical quality, focal length, zoom,aperture brightness (or speed, measured in f numbers), and cost. One or more of these will have to give ground to get one of the others. The good news is that optical quality and cost are easy to determine. The higher the cost, the better the optical quality. It is an unavoidable and almost universal truth in lenses. After you know how much you want to spend, you can narrow down the zoom, focal length and aperture. Again, I tend to steer clear of zooms greater than 3x. Focal length is a bit harder. The mid ranges 35mm-200mm tend to be cheaper (and brighter) while the short and long lenses tend to cost more. This is both because of popularity and the ease of making a good lens in a given focal length. 55mm lenses are cheaper to produce than 20mm or 500mm lenses. You will eventually want to cover a wide range of focal lengths, but start near the middle and work your way up to the more expensive lenses. By then, you will know better what you want from them, and maybe have brand preferences. The 18-70 you already have covers a pretty wide range, I wouldn't overlap too much at first. (excepting Macro) As for macro, if you are only photographing circuit boards, a 50mm macro should work fine. It won't get spooked, and you can work off a trpod under controlled lighting.Almost all macro lenses are of superb quality. That is the nice thing about them. (Note, I am not referring to the so-called zoom macros- they suck for macro, I only mean fixed length macro lenses.) Aperture, also called speed, brightness, is defined by the f number. The lower the number, the bigger the aperture and thus the brighter, or faster the lens is. Since all lenses can stop down (reduce the aperture size) you are only concerned with the biggest the aperture can be at any focal length. So, look for the lowest f# you can afford in any given focal length. The f#'s are a bit decieving too, small differences (say f 2.8 vs f4) make a huge difference in the amount of light hitting the sensor.

I hope that isn't too confusing, It is hard even for me to read.

KEH has a 50mm sigma Macro f2.8 that is a nice lens for $94 right now. They also have an abundance of 70-210 lenses, from ~$50 to $200. The $200 lens is the highly rated f4 constant aperture, one of the best zooms Minolta produced for the Maxxum mount. It won't be there long. Link to KEH zoom lenses below.

http://www.keh.com/OnLineStore/ProductList.aspx

Good luck, and keep asking. People here are very helpful and generous with their expertise.

One last word. I have never been sorry that I saved and waited for a good lens. I have been sorry several times when I jumped on a "deal".




Mercury694 is offline   Reply With Quote
Old Mar 9, 2006, 12:47 PM   #12
Member
 
Join Date: Feb 2006
Posts: 59
Default

I don't see this 70-210 f4 for $200 that you are referring to.
DJMic is offline   Reply With Quote
Old Mar 9, 2006, 12:56 PM   #13
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

DJMic wrote:
Quote:
I don't see this 70-210 f4 for $200 that you are referring to.
There is one there now in Excellent Condition for $199

If you're patient, you may be able to do better on the used market. But, KEH has a warranty with their lenses (60 days from invoice date on used gear), and you'll find their ratings to be very conservative compared to most vendors. Their return policy is better than most, too (so you can check out a lens and decide if it's as good as advertised).

http://www.keh.com/onlinestore/faq.aspx#aWarrantyPolicy

Go to the Camera Store Tab at the top of their main page.

Then, go to the Minolta Autofocus choice you'll see under 35mm.

Then, go to Zoom Lenses (where you'll see Minolta branded zoom lenses for Minolta Autofocus cameras).

There are 8 pages Minolta Autofocus Zoom lenses by default in this category there right now. But, you can change the number of items on a page (or just tell it to show you all lenses in that category on one page). You'll find one shown as 70-210mm f/4 Macro for $199

JimC is offline   Reply With Quote
Old Mar 9, 2006, 1:03 PM   #14
Member
 
Join Date: Feb 2006
Posts: 59
Default

What conditions would that lense be good for shooting?
DJMic is offline   Reply With Quote
Old Mar 9, 2006, 1:27 PM   #15
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Most outdoor conditions requring that focal range. For some subjects and distances, you may need an even longer lens.

Personally, most of my photos are on the wider end of the scale. I don't even own a lens that goes that long yet in Minolta mount.

But, if I were shooting more outdoors, with subjects located further away, I'd want something longer than I have now (my longest lens for my KM 5D is a Minolta 135mm f/2.8 ). You could also use a longer lens indoors with flash (but you'd usually want something brighter than f/4 without a flash indoors).

That particular lens is probably one I'll end up acquiring myself at some point. But, I'll wait until I see one at a bargain price first. :-)

Right this minute, they're a bit hard to come by on the used market, thanks to what appears to be some "panic buying" by KM DSLR owners in response to the Sony/KM announcements. I'll make sure to get one *before* Sony starts shipping DSLR models, too (because then, we'll have a lot more people scouring the used market for bargains). LOL

If I needed a lens for something like indoor sports, I'd probably want a brighter lens compared to the 70-210mm f/4. Something like a Sigma 70-200mm f/2.8 EX lens would probably be on my shopping list (f/2.8 is exactly twice as bright as f/4).

But, I wouldn't want to lug one around all the time for outdoor use. A brighter lens is going to be larger, heavier, and more expensive for any given focal length.

Another option in this range without about the same usability (lens brightness/focal range), would be the Minolta 70-210mm f/3.5-4.5. These are getting harder to come by, too. But, it's a bit lighter lens compared to the 70-210mm f/4.

The Minolta 70-210mm f/4 is a good compromise choice. It's not as dim as most inexpensive zoom lenses, it's much sharper with better optical quality than most, yet not as bright as the f/2.8 zooms you can find). Most users really like this lens (sharp with very good build quality for a lens at this price point and brightness).

Some advise...

I wouldn't rush out and spend a lot of money on lenses, until you have a better idea of your needs, and where you are running into limitations.

You can end up getting lenses that don 't do what you want (brightness, sharpness, focal range, Autofocus Speed, color, contrast, ergonomics, size, weight, etc.).

Any lens choice is a compromise.
JimC is offline   Reply With Quote
Old Mar 9, 2006, 1:44 PM   #16
Member
 
Join Date: Feb 2006
Posts: 59
Default

What do you think of this one for $80 bucks?

Vivitar 70-210mm f/2.8-4 APO Series 1 Autofocus Zoom Lens





Minimum Focus Distance:
3.6 ft.

Magnification:
1:[email protected]

Focus Modes:
Autofocus and Manual Focus

Aperture:
f/2.8-4.0

Aperture Range:
f/2.8-22

Filter Size:
62mm

Dimensions (DxL):
2.6 x 5.3 in. (66 x 135 mm)

Weight:
25 oz. (708g)
DJMic is offline   Reply With Quote
Old Mar 9, 2006, 1:46 PM   #17
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Junk, and I don't need any more door stops.

It's a very poor quality lens.

JimC is offline   Reply With Quote
Old Mar 9, 2006, 1:57 PM   #18
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

Here is a good source for user opinions on lenses.

Go to the bottom of this page, and select Minolta AF from the choices under User Performance Surveys.

http://www.photozone.de/8Reviews/index.html

On the page it goes to, press the Start Query button you'll find under the heading titled Browsing the Lens Database, and you'll see all lenses reported on in Minolta AF mount listed if you don't change the default parameters.

The Vivitar you're looking at is second from the very bottom, rated at an amazing low 1.08 for Optical Quality (on a scale from 1 to 5). But, it's not the very lowest quality lens you'll find, as some of the other Vivitar zooms are rated below a 1. ;-)

It's junk.

Another good source is http://www.photodo.com/nav/prodindex.html (

Select a lens manufacturer to see how a lens is rated, based on MTF charts versus user opinons. Some lenses may be listed one place but not another.

The user reviews at http://www.dyxum.com/lenses/results.asp?IDLensType=3 (link to zoom lenses) is another place to get opinions (but read the reviews versus going by the ratings, keeping in mind that these are opinions versus tests).


JimC is offline   Reply With Quote
Old Mar 10, 2006, 8:05 AM   #19
Senior Member
 
Join Date: May 2005
Posts: 338
Default

You can get a better lens than that Vivitar for the same price. (or less) The only Vivitar Series 1 lens I have heard anything good about is the 19-35- I hear that one is better than it's price would indicate, though build quality is still very low.

KEH now has a "bargain" minolta 70-210 f4 for $159, if you're interested. (I don't work there, but their site is easier to use than B&H or Adorama, IMO.)

Also on ratings, take them with a grain of salt. I think ratings are artificially low for a couple of reasons- some people think that a $70 lens should perform as a $500 lens, and more dissatisfied customers rate products than satisfied customers. Most lenses in the middle of the quality range are actuallyfairlygood lenses, and should do fine for shooting the family reunion or trip to disneyworld.
Mercury694 is offline   Reply With Quote
Old Mar 10, 2006, 8:55 AM   #20
Member
 
Join Date: Feb 2006
Posts: 59
Default

To late the 70-210 is on it's way to me already purchased.

Who knows maybe I'll have to put it on eBay.
DJMic is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 3:17 AM.