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05-22-2011, 02:34 AM   #1
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50mm old lens equivalent to 85mm digital?

Can a 50mm lens (film days/A or M) considered as an alternative to the current day 85mm digital camera lens? I would then look at it as an alternative as I am also aiming for 85mm to be in my collection but they are all expensive.

05-22-2011, 02:46 AM   #2
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No. An old 50mm lens is the same as a new 50mm lens. However, the field of view of a 85mm lens on a film camera is similar to a 50mm lens on a digital Pentax camera.
So it depends on what you want, do you want do replicate the look of a film camera with a 85mm lens? If so, a 50mm lens is an excellent option.
05-22-2011, 05:19 AM   #3
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QuoteOriginally posted by sany Quote
Can a 50mm lens (film days/A or M) considered as an alternative to the current day 85mm digital camera lens? I would then look at it as an alternative as I am also aiming for 85mm to be in my collection but they are all expensive.
No, it's the other way round. A 85mm lens used on a 35mm film camera will give app. the same angle of view, as a 50mm lens used on a Pentax DSLR.It doesn't matter, whether a lens is old or new or made for film or digital. The focal length is a fixed parameter.

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05-22-2011, 05:20 AM   #4
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When you use a 50mm lens on a digital SLR the resulting image is "equivalent" to an image taken with a 85mm lens in the film camera. The lens does not change. What changes is how much of the image is recorded. Since the sensor that replaced the film is smaller than the 35mm negative, you get less of the scene, equivalent to a 1.5x the focal lenght.
If you put an 85mm lens in a digital, the resulting image will look like an image taken with ~ 127mm (85 x 1.5) in film.
As Eric said, If you are trying to replicate the results of a 85 in film, yes a 50 in digital will do. Of course that is only in terms of field of view. There are many other factors to consider when comparing lenses.
Hope this helps.

Thanks,

05-22-2011, 06:11 AM   #5
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QuoteQuote:
When you use a 50mm lens on a digital SLR the resulting image is "equivalent" to an image taken with a 85mm lens in the film camera. The lens does not change. What changes is how much of the image is recorded. Since the sensor that replaced the film is smaller than the 35mm negative, you get less of the scene, equivalent to a 1.5x the focal lenght.
If you put an 85mm lens in a digital, the resulting image will look like an image taken with ~ 127mm (85 x 1.5) in film.
So, would not a 50mm lens on a DSLR be "equivalent" to 75mm not 85mm?
05-22-2011, 06:22 AM   #6
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If the OP wants an 85mm lens - and he makes no mention of an *35mm-film-equivalent* 85mm lens - he'll need something like the old Pentax M85mm or the new Samyang 85mm - or why not the Tamron 90mm macro?
05-22-2011, 06:42 AM   #7
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QuoteOriginally posted by TomK Quote
So, would not a 50mm lens on a DSLR be "equivalent" to 75mm not 85mm?
You are correct. I was focusing more on the concept and did not pay too much attention to the numbers itself.
05-22-2011, 07:46 AM   #8
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Thanks for bombarding me with those replies.
My idea for posting that lens was driven by some of the thread that were discussing how cheaper the old 50mm lenses are - since I was planning for a 85mm lens for a portraiture use so that i am not too close not too far from the subject. And since the 85mm new lenses were expensive, I wanted to explore this option and mainly i was concerned with the FOV same as an 85mm could provide.

Currently i am using a 35mm f2.4, which is too hard for me to capture my 2 year old daughter in action, so some what a fair distance can help me I thought and decided 85 mm would be ideal (like mentioned earlier, since I own the 35mm I don't want the 50mm as that is not too much of a difference).

So I was a bit of selfish when i thought if old 50mm can cover the view same as an 85mm I could get some for a steal, but it looks like the truth is really the opposite.

thanks again

05-22-2011, 07:57 AM   #9
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QuoteOriginally posted by sany Quote
since I own the 35mm I don't want the 50mm as that is not too much of a difference
There's actually a very large difference in the FOV between 35mm and 50mm on a crop sensor camera. 50mm is a pretty nice length for portraiture on pentax DSLRs. You would almost certainly find 85mm to be very restrictive for indoor portraiture, you won't be able to get your full subject in the frame in most rooms.
05-22-2011, 08:39 AM   #10
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Not sure if the crop factor is the same on a K-x/ K-r, but the 1.52 on the K-5 would sit you around 56mm and change.. so the absolute closest is a 55mm, lots of Super Taks and SMC tak 55's out there! Or buck up and there is a DA* 55mm.
05-22-2011, 10:40 AM   #11
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QuoteQuote:
ismaelg - You are correct. I was focusing more on the concept and did not pay too much attention to the numbers itself.
sO then to achieve a 85mm FOV in the new modern dslr will something in the range of 100mm or 135mm from the old M or K or M2s achieve?

QuoteQuote:
acrollet - There's actually a very large difference in the FOV between 35mm and 50mm on a crop sensor camera. 50mm is a pretty nice length for portraiture on pentax DSLRs. You would almost certainly find 85mm to be very restrictive for indoor portraiture, you won't be able to get your full subject in the frame in most rooms.
then what are the basic usage differences between a 50mm lens and 85mm,for indoor i can continue to use my 35mm so i thought 85mm would be an ideallength that I can look for and also that these days i hear a lot of hypes on this focal length.

QuoteQuote:
Chex - Not sure if the crop factor is the same on a K-x/ K-r, but the 1.52 on the K-5 would sit you around 56mm and change.. so the absolute closest is a 55mm,
Hi Chex, I am not following what you mentioned there in the first sentence,about that number 1.52,can you elaborate on this please..thanks
05-22-2011, 12:01 PM   #12
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QuoteOriginally posted by sany Quote
Hi Chex, I am not following what you mentioned there in the first sentence,about that number 1.52,can you elaborate on this please..thanks
As Ismael has already mentioned earlier, its a crop factor. Lets keep things simple

Film Camera: They are full frame cameras, dimension of the sensor are 36 x 24mm. Nikon D700 is an example of that.

APS-C Camera: Camera sensors are small as compared to full frame sensor. For Pentax k-r, its 23.6 x 15.8 mm. So basically the sensors are cropped by a factor of 1.5

35mm Equivalent: So if you use any lens on Digital sensor, the image circle wont match and the whole image will be cropped by the cropping factor i.e. 1.5 in all APS-C cameras
This implies to all lenses, so if you use Pentax-A 50mm F2 on your Pentax K-r, the 35mm equivalent focal length will 50mm x 1.5 = 75mm
That means if you used a 75mm lens on full frame camera and used 50mm lens on APS-C camera, both will have same field of view.

Read this to know more: Crop factor - Wikipedia, the free encyclopedia
05-22-2011, 02:02 PM   #13
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QuoteOriginally posted by sany Quote
then what are the basic usage differences between a 50mm lens and 85mm,for indoor i can continue to use my 35mm so i thought 85mm would be an ideallength that I can look for and also that these days i hear a lot of hypes on this focal length.
this may be a bit over-simplified, but a 50mm is pretty much a "portrait" length on apc-c, and 85mm is basically telephoto. I would suggest you get a zoom that covers the range and experiment to find out what length works for you. The pentax 50-200mm is available quite cheaply...
05-22-2011, 02:10 PM   #14
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QuoteOriginally posted by acrollet Quote
this may be a bit over-simplified, but a 50mm is pretty much a "portrait" length on apc-c, and 85mm is basically telephoto. I would suggest you get a zoom that covers the range and experiment to find out what length works for you. The pentax 50-200mm is available quite cheaply...
I wont recommend telephoto lens for portraits and indoor shooting. They are not as fast and snappy as primes are. DA 35mm F2.4 is a good portrait lens for indoor shooting. If you can live with Manual focus Pentax-A 50mm is a good option too. Its cheap fast and simply awesome
05-22-2011, 04:07 PM   #15
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QuoteOriginally posted by sany Quote
Thanks for bombarding me with those replies.
My idea for posting that lens was driven by some of the thread that were discussing how cheaper the old 50mm lenses are - since I was planning for a 85mm lens for a portraiture use so that i am not too close not too far from the subject. And since the 85mm new lenses were expensive, I wanted to explore this option and mainly i was concerned with the FOV same as an 85mm could provide.

Currently i am using a 35mm f2.4, which is too hard for me to capture my 2 year old daughter in action, so some what a fair distance can help me I thought and decided 85 mm would be ideal (like mentioned earlier, since I own the 35mm I don't want the 50mm as that is not too much of a difference).

So I was a bit of selfish when i thought if old 50mm can cover the view same as an 85mm I could get some for a steal, but it looks like the truth is really the opposite.

thanks again
I think you are getting yourself confused by the crop factor concept. The concept is only useful if you have shot with 35mm film cameras a lot, otherwise it is completely useless and the source of confusion for newbies.

If 35 f.5 is too short, then I think you would be better off looking for a DA 70mm. I do think 50 & 35 is too close, especially if you have only 1 prime currently. Actually maybe a DA 55-300 would be good if you don't already own one.

I assume you have a kit lens, use that to confirm what focal length you want.

Forget crop factor!
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