Olympus C5050 zoom teleconverter test.

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Comparative tests (and other observations) of two different Tele Converters and Digital Zoom on an Olympus C5050 Zoom digital camera regarding Magnification, Chromatic Aberrations (CA), and Image Sharpness

by Jens Birch
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Tested tele configurations: (focal lengths (FL) are given as the cameras zoom setting in 35 mm format equivalents):

Raynox DCR-1850 Pro tele converter (nominal magnification; 1.85 x), mounted on the special Raynox (41-52 mm) adapter tube, at maximal zoom (FL=101 mm) and at the limit of vignetting (FL=64 mm). (appr. $140 in Sweden, 2003)
Unknown brand with the text; 'TL-1700 Tele Converter 2.0 x, Made in Japan' on the housing, mounted on the Olympus CLA-1 (41-43 mm) adapter tube via a 43-46 step ring, at maximal zoom (FL=101 mm). ($22 at a second hand photo store)
Maximal zoom (FL=101 mm), without tele converter but with ~1.7 x digital zoom (giving the same imaged area as with the teleconverters).
Maximal zoom (FL=101 mm), without tele converter was tested at the same distance as with tele converters as reference for Magnification tests, and at a closer distance (~60% of the distance in the other tests), giving the same imaged area as with the teleconverters, as a reference for Chromatic Aberrations and Sharpness tests.

Here is a picture of the tele converters (so you can avoid the TL-1700...) mounted on their respective adapters together with an AA battery for size comparison.

Some observations about the teleconverters:

Size (including adapter):	- The Raynox DCR-1850 is a large chunk of glass; 85 mm outer diameter, 80 mm length, and the weight is almost 0.3 kilograms. - The TL-1700 more normal in size; 67 mm outer diameter, 69 mm length, and the weight is only 0.17 kilograms.
Viewfinder obstruction:	- The large diameter of the DCR-1850 totally obstructs more than half the viewfinder which makes it nessecary to use the LCD. It is possible to use the viewfinder but requires a good deal of guessing of what you are shooting. - The TL-1700 does not obstruct any part of the viewfinder that corresponds to the imaged area. It is easy to learn approximately how much of the viewfinder that corresponds to the imaged area.
Vignetting	- The DCR-1850 causes vignetting below 64 mm focal length. - The TL-1700 causes vignetting below 95 mm focal length
Flash shadowing	- The DCR-1850 shadows the internal flash over a large area in the lower left (more than just the corner) at maximal zoom (101 mm focal length). - The TL-1700 gives a faint shadow just in the corner tip.
Adapter tubes	- The Raynox adapter tube has 52 mm filter threads. This produces shadowing of the internal flash as well as some obstruction of the viewfinder. it is also 5 mm longer than the Olympus CLA-1adapter but does not cause vignetting without filter. The treads on the Raynox adapter that goes into the camera body has only 1½ turns which I think is too little considering that it is holding 300 grams of expensive glass! The look of the subdued black Raynox adapter is a bit more slick than the CLA-1.
Miscellaneous:	- No reduction of the f-number could be detected for any of the two tele converters. - No filter treads on any of the tele converters - Both housings are made of plastic, including the treads! (Be careful.)

Test conditions:

For each configuration, the Magnification and Chromatic Aberration was tested by taking head-on photos of the front page of the Olympus C5050 Zoom Reference Manual (Fig. 1) in daylight and the Image sharpness was tested by taking photos of a brick wall. The camera was set to aperture priority mode, otherwise with the factory default camera settings. The pictures were taken in HQ resolution (2560x1920 pixels fairly low compressed JPEG)
.
Overview of the test image

Figure 1. The front page of the Olympus C5050 Zoom Reference Manual with some regions of interest used for the magnification and chromatic aberration tests.

Magnification tests:

The magnification power was mesured by taking the ratio of the horizontal lengths (in pixels) of the checkered region in two photos, taken with and and without tele converter, of the C5050 camera manual front page.

Results:

Raynox DCR-1850 Pro: 1.70x magnification
TL-1700: 1.67x magnification

Comment: Raynox specifies a too high 1.85x magnification both at their home page and in the documentation with the device.
On the TL-1700 it is written "2.0 x" on the device which is not the correct magnification.

Chromatic Aberration (CA) tests:

The front page of the Olympus C5050 Zoom Reference Manual was photographed in daylight, overcast using aperture f/4.0 when taking the photos with the Raynox DCR-1850 and the digital zoom and sunny using aperture f/5.0 with the other set-ups.
Two regions of each test shot, the center 400x300 pixels and 400x300 pixels close to a corner (see image below) are presented at full resolution in table I.

Table I. Full resolution cut-outs of the chromatic aberration test images.
Row numbers correspond to the configuration numbers given above.
Columns: 1. Show 400x300 pixels in the image center. 2. Show 400x300 pixels in the upper left corner. (According to Fig 1.)

1:1. Raynox DCR-1850 Pro 400x300 pixels at center	1:2. Raynox DCR-1850 Pro 400x300 pixels at upper left corner

2:1. TL-1700 Tele Converter 400x300 pixels at center	2:2. TL-1700 Tele Converter 400x300 pixels at upper left corner

3:1. FL=101 mm + 1.7 x Digital Zoom 400x300 pixels at center	3:1. FL=101 mm + 1.7 x Digital Zoom 400x300 pixels at upper left corner

4:1. 101 mm at ~60% distance (as reference) 400x300 pixels at center	4:1. 101 mm at ~60% distance (as reference) 400x300 pixels at upper left corner

Comments: The Chromatic Aberrations (CA) can be seen as a rainbow-like color separation around edges of features with large contrast. The different colors of the images are mostly due to different light conditions for the diffrerent shots.

DCR-1850 exhibits some CA.
TL-1700 exhibits considerably more CA.
1.7 x Digital Zoom does not give any visible CA but it exhibits a considerably inferior image quality due to virtually larger pixels and anomalous contrast effects (presumably due to image processing issues of the camera).
101 mm at ~60% distance shows very small tendency of CA.

Bottom line:

Raynox DCR-1850 Pro is the best choice.
TL-1700 gives unacceptable amount of cromatic aberrations.
Digital zoom can't be used for high contrast subjects.
It is better go go closer if possible.

Image sharpness tests:

In order to see how the different configurations perform on a subject with less contrast, this comparison was made.

Row numbers correspond to the configuration numbers given above.
Column 1 shows full picture overview resized to 400x300 pixels. Column 2 show full resolution 400x300 pixels from the image center. Column 3 show full resolution 400x300 pixels from the upper left corner corner.

1:1. Raynox DCR-1850 Pro Overview	1:2. Raynox DCR-1850 Pro Center 400x300 pixels	1:3. Raynox DCR-1850 Pro Corner 400x300 pixels

2:1. TL-1700 Tele Converter Overview	2:2. TL-1700 Tele Converter Center 400x300 pixels	2:3. TL-1700 Tele Converter Corner 400x300 pixels

3:1. FL=101 mm + 1.7 x Digital Zoom Overview	3:2. FL=101 mm + 1.7 x Digital Zoom Center 400x300 pixels	3:3. FL=101 mm + 1.7 x Digital Zoom Corner 400x300 pixels

4:1. 101 mm at ~60% distance Overview	4:2. 101 mm at ~60% distance Center 400x300 pixels	4:3. 101 mm at ~60% distance Corner 400x300 pixels

Comments: All photos are taken with aperture f/4.0.

DCR-1850 gives good sharpness in the center but some blurr at the corner. The effects are not visible at reduced size.
TL-1700 gives some blurr in the center but HUGE blurr at the corner. The effects are visible at reduced size.
1.7 x Digital Zoom gives the same unsharp image in the center as at the corner. The contrast problem seen in the CA-test is not apparent here. The effects are not visible at reduced size.
101 mm at ~60% distance gives clear images all over the picture.

Bottom line:

Raynox DCR-1850 Pro is the best choice.
TL-1700 gives unacceptable amount of blurr.
Digital zoom can be used for normal contrast subjects.
It is better go go closer if possible.

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