How does FE 55mm perform in crop as a 85mm lens??

Started Jan 21, 2014 | Discussions
zither Regular Member • Posts: 240
How does FE 55mm perform in crop as a 85mm lens??

I'm currently having A7 and Nikon 85mm/f1.8 D lens with adaptor.

FE 55mm got very good review as a standard prime. But i'm just wondering how it will perform under crop mode as a 85mm (82.5mm precisely) compared with the Nikon lens.

I know I will only be able to use 10M pixels out of A7, but I also got AF so it's not a bad deal and 10M is enough for most of my usages.

My biggest concerns are DOF, IQ and shutter speed. Will they be shallower/better or at least comparable with the Nikon lens or any other 85mm full frame prime under the same aperture settings?

 zither's gear list:zither's gear list
Sony RX100 IV Sony a7R II Sony FE 55mm F1.8 Fujifilm XF 10-24mm F4 R OIS Sony Vario-Tessar T* FE 16-35mm F4 ZA OSS +1 more
Sony a7
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SQLGuy Veteran Member • Posts: 6,311
Re: How does FE 55mm perform in crop as a 85mm lens??

There will be more DOF from a 55/1.8 @ 1.8 cropped than from an 85/1.8 @ 1.8 FF.

IQ is good: http://www.dpreview.com/forums/post/52878225

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A7 with kit lens and a number of legacy lenses (mostly Canon FD)

 SQLGuy's gear list:SQLGuy's gear list
Canon PowerShot G9 Nikon D200 Sony Alpha DSLR-A900 Sony Alpha NEX-7 NEX-5T +13 more
Kiril Karaatanasov Senior Member • Posts: 2,098
Re: How does FE 55mm perform in crop as a 85mm lens??

zither wrote:

I'm currently having A7 and Nikon 85mm/f1.8 D lens with adaptor.

FE 55mm got very good review as a standard prime. But i'm just wondering how it will perform under crop mode as a 85mm (82.5mm precisely) compared with the Nikon lens.

I know I will only be able to use 10M pixels out of A7, but I also got AF so it's not a bad deal and 10M is enough for most of my usages.

My biggest concerns are DOF, IQ and shutter speed. Will they be shallower/better or at least comparable with the Nikon lens or any other 85mm full frame prime under the same aperture settings?

I use the lens in it's full frame glory. It ties a bit of practice for accurate and reliable focusing. It is bait frustrating until you get used to small, big zones and the shallow DOF.

For portraits 55 is a bit of a challenge but manageable. Distortion can become a problem right?

In terms of sharpness I would say on 24MP it is similar to the Nikon 85/1.8 G (I used the later with D600).

50/1.8 on crop is an ooh option for portraits. Perspective is same as 85mm on full frame. I used 50/1.8 on NEX-7 a lot. Problem is when you take picture that is full length or waist and up... the DoF is just not the same as 85/1.8 on full frame. Even the 55/1.8 on A7 is better than 55/1.8 would be on crop.

So perhaps you may use cropped mode for close ups - may be step back and leave room for cropping in post processing.

When you want a full length then you may be better off just using the lens in its full frame glory.

Inserting pictures here is nightmare so you can loo into my gallery on Flickr.

http://www.flickr.com/photos/kirilk/

 Kiril Karaatanasov's gear list:Kiril Karaatanasov's gear list
Sony a6300 Sony a7R III
OP zither Regular Member • Posts: 240
Re: How does FE 55mm perform in crop as a 85mm lens??

This actually bring me another question:

How does the DOF get computed when using FE55 in crop mode?

Actually, I'm pretty sure FE55 will give good IQ in most case, but really not sure about the the DOF and shutter speed.

Could anybody rank the DOF and Shutter speed using the following combinations? assuming the settings are the same.

A7 + FE 55 full mode

A7 + FE 55 crop mode

A7 + Nikon 85 full mode

NEX + FE 55 crop mode

 zither's gear list:zither's gear list
Sony RX100 IV Sony a7R II Sony FE 55mm F1.8 Fujifilm XF 10-24mm F4 R OIS Sony Vario-Tessar T* FE 16-35mm F4 ZA OSS +1 more
tesilab
tesilab Veteran Member • Posts: 3,001
Re: How does FE 55mm perform in crop as a 85mm lens??

You should check a site like http://www.dofmaster.com/ to get an idea of DOF with different focal lengths at the same aperture.

 tesilab's gear list:tesilab's gear list
Sony RX1R II Panasonic Lumix DMC-GX8 Sony a7 III Panasonic Leica Summilux DG 25mm F1.4 Sony FE 85mm F1.8 +1 more
dave92029 Contributing Member • Posts: 802
Re: How does FE 55mm perform in crop as a 85mm lens??

Kiril Karaatanasov wrote:

zither wrote:

I'm currently having A7 and Nikon 85mm/f1.8 D lens with adaptor.

FE 55mm got very good review as a standard prime. But i'm just wondering how it will perform under crop mode as a 85mm (82.5mm precisely) compared with the Nikon lens.

I know I will only be able to use 10M pixels out of A7, but I also got AF so it's not a bad deal and 10M is enough for most of my usages.

My biggest concerns are DOF, IQ and shutter speed. Will they be shallower/better or at least comparable with the Nikon lens or any other 85mm full frame prime under the same aperture setting

Inserting pictures here is nightmare so you can loo into my gallery on Flickr.

http://www.flickr.com/photos/kirilk/

Thank you for the link to your Flicker gallery.  Glancing at your images, it is very apparent when you switched to the a7 from the NEX 7. There is a very noticeable improvement in the IQ between the two camera bodies. I don't know how much of this improvement was due to different glass, if any or simply the aps-c vs FF, but it is a big difference in IQ.

Dave

 dave92029's gear list:dave92029's gear list
Sony a7 III Sony FE 55mm F1.8 Sony FE 28mm F2 Sony 1.4x Teleconverter (2016) Sony FE 100-400mm F4.5-5.6
viking79
viking79 Forum Pro • Posts: 14,148
Re: How does FE 55mm perform in crop as a 85mm lens??

zither wrote:

This actually bring me another question:

How does the DOF get computed when using FE55 in crop mode?

Depth of field is based on aperture size and focal length, so depth of field of the FE 55mm f/1.8 on APS-C is the same as on full frame. What is different is your field of view (the APS-C is just a crop of the image you would get from the full frame). So the 55mm f/1.8 use on APS-C will give the same field of view and depth of field as an 85mm f/2.8 used on full frame, both have an entrance pupil/apparent aperture size of about 31mm (55 / 1.8 ~= 85 / 2.8).

Actually, I'm pretty sure FE55 will give good IQ in most case, but really not sure about the the DOF and shutter speed.

Same as any other 55mm f/1.8 lens on APS-C, or again, same as 85mm f/2.8 on full frame.

Could anybody rank the DOF and Shutter speed using the following combinations? assuming the settings are the same.

Set the full frame at 1 1/3 stop higher ISO to maintain shutter speed with aperture set 1 1/3 stop smaller (same composition), set the same ISO and longer shutter speed to improve image quality, set the same aperture and 1 1/3 stop higher ISO to get higher shutter speed but less depth of field, etc. It is a trade off with full frame, it only adds flexibility.

A7 + FE 55 full mode

55mm f/1.8. In APS-C terms this is 35mm f/1.2. 24 MP

A7 + FE 55 crop mode

Still a 55mm f/1.8, just like you cropped the above image after taking it. In FE terms this is 85mm f/2.8. 10 MP.

A7 + Nikon 85 full mode

85mm f/1.8, in APS-C terms this is 55mm f/1.2 24 MP

NEX + FE 55 crop mode

Still a 55mm f/1.8, same as A7 in crop mode. 16 or 24 MP (whatever your NEX is)

So focal length and aperture are both fixed properties of a lens that never change no matter what camera you put them on, but to get an "equivalent" image, you have to multiply the focal length and aperture by the crop factor.

Eric

 viking79's gear list:viking79's gear list
Sony a7R Samsung NX1 Samsung NX 30mm F2 Pancake Samsung NX 85mm F1.4 ED SSA Samsung NX 60mm F2.8 Macro ED OIS SSA +5 more
OP zither Regular Member • Posts: 240
Re: How does FE 55mm perform in crop as a 85mm lens??

viking79 wrote:

zither wrote:

This actually bring me another question:

How does the DOF get computed when using FE55 in crop mode?

Depth of field is based on aperture size and focal length, so depth of field of the FE 55mm f/1.8 on APS-C is the same as on full frame. What is different is your field of view (the APS-C is just a crop of the image you would get from the full frame). So the 55mm f/1.8 use on APS-C will give the same field of view and depth of field as an 85mm f/2.8 used on full frame, both have an entrance pupil/apparent aperture size of about 31mm (55 / 1.8 ~= 85 / 2.8).

Actually, I'm pretty sure FE55 will give good IQ in most case, but really not sure about the the DOF and shutter speed.

Same as any other 55mm f/1.8 lens on APS-C, or again, same as 85mm f/2.8 on full frame.

Could anybody rank the DOF and Shutter speed using the following combinations? assuming the settings are the same.

Set the full frame at 1 1/3 stop higher ISO to maintain shutter speed with aperture set 1 1/3 stop smaller (same composition), set the same ISO and longer shutter speed to improve image quality, set the same aperture and 1 1/3 stop higher ISO to get higher shutter speed but less depth of field, etc. It is a trade off with full frame, it only adds flexibility.

A7 + FE 55 full mode

55mm f/1.8. In APS-C terms this is 35mm f/1.2. 24 MP

A7 + FE 55 crop mode

Still a 55mm f/1.8, just like you cropped the above image after taking it. In FE terms this is 85mm f/2.8. 10 MP.

A7 + Nikon 85 full mode

85mm f/1.8, in APS-C terms this is 55mm f/1.2 24 MP

NEX + FE 55 crop mode

Still a 55mm f/1.8, same as A7

in crop mode. 16 or 24 MP (whatever your NEX is)

So focal length and aperture are both fixed properties of a lens that never change no matter what camera you put them on, but to get an "equivalent" image, you have to multiply the focal length and aperture by the crop factor.

Eric

Thanks a lot for your details info. So overall, shooting FE55 in crop mode is exactly the same as I shooting in FF mode and crop it in post-processing.

Ok, then looks like it doesn't make me any benefit (except storage size) by shooting FF lens in crop mode. Even in EVF or LCD, it's equivalent to a enlarged picture from a portion of my original one.

 zither's gear list:zither's gear list
Sony RX100 IV Sony a7R II Sony FE 55mm F1.8 Fujifilm XF 10-24mm F4 R OIS Sony Vario-Tessar T* FE 16-35mm F4 ZA OSS +1 more
radissimo
radissimo Regular Member • Posts: 144
Re: How does FE 55mm perform in crop as a 85mm lens??

Yes , the main advantage to shoot in crop mode in this scenario is better framing of the shot.

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Sigma DP2 Merrill Ricoh GR Panasonic LX100 Canon PowerShot G7 X Canon G7 X II +5 more
socode Regular Member • Posts: 356
Re: How does FE 55mm perform in crop as a 85mm lens??

viking79 wrote:

Depth of field is based on aperture size and focal length, so depth of field of the FE 55mm f/1.8 on APS-C is the same as on full frame.

It's not the same, you should work to a smaller circle of confusion on the smaller format. DoF varies by subject distance too.

Julienrld
Julienrld New Member • Posts: 6
Re: How does FE 55mm perform in crop as a 85mm lens??

Are there any pics out there to show the difference ??
Thanks

Julienrld
Julienrld New Member • Posts: 6
Re: How does FE 55mm perform in crop as a 85mm lens??

a little precision : if someone could be kind enough to shoot the same subject entirely (so to move when using the crop mode to get the same field of view - to compare sharpness and DOF)

thanks for your help !!

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