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11-02-2017, 10:00 AM   #1
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HD Pentax-D FA* 70-200mm on a K-70???

Im eventually replacing my broken 55-300mm w/ the newer 55-300mm RE.

But I'm also contemplating splurging for the 70-200mm.

What would the Full Frame numbers translate on a K-70 body?

50-180?

Triple the price sounds crazy.

11-02-2017, 10:05 AM   #2
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70-200mm F2.8 also on the K-70. The focal length is a lens property and doesn't depend on the camera.

The D FA* 70-200 is more expensive due to it's large max. F-stop of 2.8. Also note that it remains at F2.8 through the entire zoom range.
11-02-2017, 10:30 AM   #3
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QuoteOriginally posted by BATMON Quote
What would the Full Frame numbers translate on a K-70 body?
There is no such thing. Your 55-300 is 55-300 and the 70-200 is 70-200. So the DFA*70-200 would have a much smaller focal range than your 55-300. It is also massive in comparison and far more expensive. You pay (both in weight and money) for the constant f/2.8 as well as the '*' optics and sealing.
Think that over carefully, before deciding. They are different lenses for different purposes. The DFA*70-200 is by all accounts as good a lens as Pentax has ever made but unless you are comfortable carrying it around it might get left home more than you take it. Also consider the older DA*60-250 f/4. Much smaller but still f/4 and an excellent lens I upgraded from the 55-300 to the 60-250 and have been very happy with it. It is still much heavier than the 55-300 so it stays home sometimes, but nothing like the huge 70-200.
11-02-2017, 10:37 AM   #4
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QuoteOriginally posted by Ole Quote
Also note that it remains at F2.8 through the entire zoom range.
So I cant do F11 if I wanted to photograph a group of people?

11-02-2017, 10:56 AM   #5
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What Ole means is that the maximum aperture on the 70-200 doesn't change throughout the zoom range, whereas on the 55-300 PLM for example, it changes from f4.5 at the wide end to f6.3 at the long end. The fact that this happens of course doesn't change where you can set the aperture: f11 is f11 on both lenses. You can set it where you want - except obviously, not wider than the maximum aperture.

While the focal length doesn't change, the field of view does change because the APS-c sensor is smaller, so that it only covers the centre of the image circle. So a 35mm lens would give a 'standard' perspective field of view on APS-c, and it would be a moderate wide on 35mm format. Similarly, a 50mm would be a short tele on APS-c (standard on 35mm format). Consequently the 70-200 would offer a 105-300-equivalent field of view on APS-c due to the smaller sensor - but the focal length itself does not change.

Hope this helps.
11-02-2017, 11:05 AM   #6
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QuoteOriginally posted by microlight Quote
Consequently the 70-200 would offer a 105-300-equivalent field of view on APS-c due to the smaller sensor - but the focal length itself does not change.
This....thanx.
11-02-2017, 11:11 AM   #7
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QuoteOriginally posted by BATMON Quote
So I cant do F11 if I wanted to photograph a group of people?
No no no...

The f/2.8 "through the entire range" is referring to ONLY the widest opening option. Many lenses have a variable aperture that is wider on one end of the range and narrower (effectively) on the longer end. The DA 55-300 is one of those variable aperture lenses. All of these have f/stops that are much narrower.

Also I want to address the "full frame lens vs. crop lens". The focal length doesn't care what the lens was made for. The way the lens appears in the viewfinder and on the sensor cares.

So if I put a 300mm lens on an 8x10" view camera - that lens put on a crop body will give the same basic image as a 300mm crop frame lens. The crop frame lens on an 8x10" view camera will not work - as it will fail to cover the entire area of the camera negative but the portion that will be illuminated will in fact look the same as it would from the original 300mm view camera lens.

The portion you see when using a lens is a lot like a window in the wall of your house. Imagine you have a 2x3' lens and you are seated 10' from it. If you then enlarge the window to 4'x6' you will see more things in the window - the window will show a wider amount of stuff. Effectively the window will give you a wider angle view without any change in the outside world or the "lens" (glass with no optical impact in the window).

This is why if I put a 300mm lens on a "full frame" camera that is a full frame lens and covers the entire area (like the 70-200 f/2.8 DFA) it will appear LESS telephoto in terms of what is captured than it will on a "crop frame" camera like the K-70. The crop frame lens on the other hand at the same focal length still shows the same image on the crop frame camera as the full frame lens. So if you put the DFA 70-200 f/2.8 on the K-70 at 100mm and the DA 55-300 at 100mm the basic image will be similar (quality and exposure available may vary but the overall view of the subject will be similar). The DA 55-300 placed on a K-1 will fail to cover the entire sensor and will vignette badly or even black out entirely in the corners and edges because it is not designed to have a large enough area covered by the light going through it to be used on a Full Frame sensor.

Any other arguments about equivalence and so forth are all about comparing perspective - but NONE of those are about the LENS being a different type - only about using the focal lengths on the various sensors. Any lens of XYZ focal length is going to give the same basic image view on any sensor as long as it has an image circle (fancy name for a window) that covers the full size of the sensor.

---------- Post added 11-02-17 at 02:14 PM ----------

QuoteOriginally posted by microlight Quote
Consequently the 70-200 would offer a 105-300-equivalent field of view on APS-c due to the smaller sensor - but the focal length itself does not change.

Hope this helps.
Yes but what is missing is that the DA 55-300 also offers an equivalent view of 82.5mm - 450mm - the equivalence isn't based on the lens being full frame it is based on the size of the sensor relative to the focal length on some standard size that you are measuring against. The implication that the DFA will appear longer than it is on the D70 relative to a similar DA is just confusion and is what I think the OP has in his head.

Put another way - any 200mm will have a 300mm equivalent field of view when used on a crop (APSC) sensor - RELATIVE to a 200mm or 300mm placed on a Full Frame sensor. It is simply NOT true that a DFA lens will look longer at a given focal length than a DA lens of the same focal length when viewed on any sensor. (The DA will of course fail to cover the full sensor of anything larger than a crop sensor in most cases).

Last edited by UncleVanya; 11-02-2017 at 11:16 AM.
11-02-2017, 11:25 AM   #8
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I already own the 70mm so I was looking to get past that length, and "upgrade" from the 55-300mm.
Or just stay within the 55-300mm RE price range.

I hardly ever shot over 250+ on my previous 55-300mm.

11-02-2017, 11:31 AM - 2 Likes   #9
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If you took your 55-300 and set it to 70 on the zoom ring, and took a picture, that would be just like 70 mm with the D-FA lens. Same with going to 200 on the 55-300; it'd be the same as 200 on the big lens. The image quality and all that jazz, the rendering, would be a bit different because they're different lens designs. But as far as how wide the view would be, it would be like someone put some stops in the 55-300 so that it couldn't go wider than 70 and longer than 200.

You would gain a wider maximum aperture for better light grabbing, and improved image quality due to lens design and having a full frame lens on a crop body.
11-02-2017, 11:34 AM - 3 Likes   #10
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QuoteOriginally posted by microlight Quote
Consequently the 70-200 would offer a 105-300-equivalent field of view on APS-c due to the smaller sensor - but the focal length itself does not change.
No, that is wrong.
The first problem is that a most important part is missing from your statement: equivalent to what?0
The second problem, obvious once we answer the first: there's no point for an APS-C user to relate to a system he's not using (FF). Conversion factors are an unnecessary complication.
The third problem is the temptation to apply those unnecessary conversion factors to FF lenses only (instead of all the lenses). Which I get the feeling it's happening here.

The proper answer is: the focal length is independent of the sensor size, period. It's also independent of the lettering on the barrel (e.g. those DA, D FA etc.markings)
So you can directly compare the 70-200mm with the 55-300, and at every common focal length the angle of view will be the same (camera being the same format, of course).
11-02-2017, 11:35 AM   #11
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QuoteOriginally posted by BATMON Quote
I already own the 70mm so I was looking to get past that length, and "upgrade" from the 55-300mm.
Or just stay within the 55-300mm RE price range.

I hardly ever shot over 250+ on my previous 55-300mm.
Still not sure what you are saying. The 70-200 will be the same as setting the 55-300 to 70-200 but will offer better optical quality, and f/2.8 for low light use even at 200mm which the 55-300 will not. It will be heavier and larger and more expensive. It will also work well should you ever want to use a K-1 since it is full frame. It will NOT appear to be equivalent to the 55-300 set to 100-300. That is what I am trying to convey. Sorry if that hasn't been clear and sorry if you already understood that.
11-02-2017, 11:36 AM   #12
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QuoteOriginally posted by UncleVanya Quote
Still not sure what you are saying. The 70-200 will be the same as setting the 55-300 to 70-200 but will offer better optical quality, and f/2.8 for low light use even at 200mm which the 55-300 will not. It will be heavier and larger and more expensive. It will also work well should you ever want to use a K-1 since it is full frame. It will NOT appear to be equivalent to the 55-300 set to 100-300. That is what I am trying to convey. Sorry if that hasn't been clear and sorry if you already understood that.
Yeah I got it.

Optical quality is my desire.
11-02-2017, 11:40 AM - 1 Like   #13
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QuoteOriginally posted by BATMON Quote
Yeah I got it.

Optical quality is my desire.
Then look no further! That's a nice lens. The other option would be to look at the DA* 60-250 f/4 - if speed is not a huge requirement and SDM focusing speed is acceptable. The lens is lighter and smaller and offers a great deal of very high quality optics. The DA* 50-135 is another option but gives up range for speed (f/2.8). Neither lens works on a full frame completely - though the DA* 60-250 can be modified to make it very very good on Full Frame (not quite perfect - some would say).

Other options are the 100-300 f/4 Sigma (expensive and hard to find) and the Tamron and Sigma 70-200 f/2.8 variants that are cheaper and lighter than the DFA option.
11-02-2017, 11:41 AM - 1 Like   #14
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Similar combo...

I shoot a K-3 in the wild. I used to use the 55-300, great, light, but needed more light. I moved up to the 60-250 F4 DA*. Exceptional lens in all ways, light, small (for what it is), world class IQ. Wanted more light, moved up to 70-200 DFA*. Similar IQ to the 60-250 DA*, better at low light. Heavy.. no make that HEAVY. But for work afield, no ZOOM creep (extending from gravity) while walking. I wanted the larger aperture, was willing to trade off weight. If you don't plan on going to FF or use a TC a lot, I'd look at the 60-250 DA*. Great price too. NEVER had any issues with it.
11-02-2017, 11:42 AM   #15
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It's a cost, weight, and size increase. Make sure you're okay with that.

You could also get some improvement by going to a 3rd party lens. Sigma and Tamron 70-200's, f2.8's, are available new or used right now. The D-FA* 70-200 is head and shoulders better but you may not notice as much when using a crop body like the K-70.
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